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F40 6 Speed 3.09 Final Drive Upgrade by fieroguru
Started on: 08-20-2017 05:22 PM
Replies: 65 (3647 views)
Last post by: sourmash on 11-22-2020 08:17 PM
fieroguru
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Report this Post09-08-2017 05:53 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
I had a guy email me about what I would charge to do the 3.09 final drive swap and ship him the transmission once done. Here is a rough breakdown of costs. Like I said earlier, this isn't an inexpensive upgrade.

$1100 - zero mile MT2 F40.
$950 - 3.09 F40 purchased in the UK and shipped to the US
$250 - new bearings for the main shafts, ARP bolts for differential, shims, and other supplies
$500 - labor for the disassembly, machining of VSS boss and case for starter clearance, and reassembly
$175 - shipping the hybrid 3.09 F40 to the customer

$2975 total and the lead time could be 3-6 weeks.

$1250 additional if you wanted a Quaife Limited Slip

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Report this Post09-09-2017 01:56 PM Click Here to See the Profile for J GunsettClick Here to visit J Gunsett's HomePageClick Here to Email J GunsettSend a Private Message to J GunsettEdit/Delete MessageReply w/QuoteDirect Link to This Post
Paul, how is the fuel milage working out with the 3.09? And what size tire are you running on the rear of the Fiero?

Thanks, Jack
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Report this Post09-09-2017 06:31 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
My first trip was 287 miles at 75 mph and averaged 28 mpg. I want to do another one at 70 mph to see if I can't get over 30 (my 29 mpg with the other wheels and tires was at 70 mph) . The 235 and 285 tires certainly are not helping the mpg. My rear tires are 24.8" tall.

The next one I am going to bring the laptop and scan the drive. I want to make sure the timing in the lower RPM/higher load cells is where it needs to be.
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Report this Post09-14-2017 06:28 PM Click Here to See the Profile for Alex4mulaClick Here to Email Alex4mulaSend a Private Message to Alex4mulaEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fieroguru:

I had a guy email me about what I would charge to do the 3.09 final drive swap and ship him the transmission once done. Here is a rough breakdown of costs. Like I said earlier, this isn't an inexpensive upgrade.

$1100 - zero mile MT2 F40.
$950 - 3.09 F40 purchased in the UK and shipped to the US
$250 - new bearings for the main shafts, ARP bolts for differential, shims, and other supplies
$500 - labor for the disassembly, machining of VSS boss and case for starter clearance, and reassembly
$175 - shipping the hybrid 3.09 F40 to the customer

$2975 total and the lead time could be 3-6 weeks.

$1250 additional if you wanted a Quaife Limited Slip


Now you are making me want to break my current F40 I already have a spare new F40.
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Report this Post11-17-2020 10:04 PM Click Here to See the Profile for ArchieClick Here to visit Archie's HomePageClick Here to Email ArchieSend a Private Message to ArchieEdit/Delete MessageReply w/QuoteDirect Link to This Post
Hey guru, How's it going?

Back when I had my Shop in Rockford, we disassembled 5 or 6 F40's to have the internals Cryo'ed.

I took part in disassembly of the first one, then Rob & Kris disassembled the rest of them.

So, the problem is old age, I can't recall how to unlock this mechanism. Can you let me know?

Archie 847-212-3909 or Archie@v8archie.com or just reply here.

Thanks a lot.

Archie

Edited to add....... I figured it out. It was the simplest thing in the whole teardown.

Thanks

Archie


 
quote
Originally posted by fieroguru:


Under the gear set removed by pry bars is a different locking mechanism. There is an outer ring holding two half moon pieces with a locking tab that fits into the hole.


[This message has been edited by Archie (edited 11-18-2020).]

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fieroguru
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Report this Post11-18-2020 07:11 AM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Archie:
So, the problem is old age, I can't recall how to unlock this mechanism. Can you let me know?

Archie


Once you have it disassembled this far, the only thing holding the next gear in place are the two C-clips that slide into a groove in the shaft. They slide right out and away from the shaft, then the gear can slide off.

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Report this Post11-19-2020 10:45 AM Click Here to See the Profile for Rickady88GTClick Here to Email Rickady88GTSend a Private Message to Rickady88GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
Guru, you have said that 1st and 2nd gear ratios are a part of the shafts, I see the differential drive gear at the end of the shaft. But where is the input gear for the shaft? I assume it is the synchro gear,..correct? Could it be possible to change out those gear sets?
My train of thought is a higher first and a lower second. I know I have mentioned this before and you gave an answer, but I still haven't understood why the first and second are permanent?
Thanks for your patience with my questions.
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Report this Post11-19-2020 11:43 AM Click Here to See the Profile for WillClick Here to Email WillSend a Private Message to WillEdit/Delete MessageReply w/QuoteDirect Link to This Post
It's easier to manufacture everything that way.

A taller first is something a hairy problem. In reverse, power flows from the first input gear (input shaft) to the first output gear (lower output shaft) to the reverse gear (upper output shaft) to the final drive. The first output gear and reverse gear are permanently meshed. This allows reverse to the synchronized, since the reverse gear runs on the upper output shaft just like 3rd and 4th.

This means that for the first input to be larger and first output to be smaller (taller first), the reverse gear must grow as well. While there's always room to make a large gear smaller, and almost always room to make a small gear larger, having the space to make a large gear larger is not a foregone conclusion.

[This message has been edited by Will (edited 11-19-2020).]

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fieroguru
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Report this Post11-19-2020 08:01 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Rickady88GT:

Guru, you have said that 1st and 2nd gear ratios are a part of the shafts, I see the differential drive gear at the end of the shaft. But where is the input gear for the shaft? I assume it is the synchro gear,..correct? Could it be possible to change out those gear sets?
My train of thought is a higher first and a lower second. I know I have mentioned this before and you gave an answer, but I still haven't understood why the first and second are permanent?
Thanks for your patience with my questions.


The two shafts that this thread focused on are the Main Upper and Main Lower, which are also the two output shafts. These both have the pinion gear formed and cut into the actual shaft. We are fortunate in that GM offered several versions with different gear ratios. 3.091, 3.348, 3.545 (G6), 3.762, 3.895, 3.909, 4.176. Since the G6 version came with the 3.545, we have options for shorter and longer gears.

The shaft the clutch disk rides on is the input shaft and 1st and 2nd gear are formed into the shaft. Here is a drawing of what the input shaft looks like.


If only one gear had been formed into the input shaft, you would be able to change gear ratios independently... but that simply isn't the way GM did it, so we can only swap 1st and 2nd gears as a paired unit. There are 4 pairs from GM: 3.769/2.040 (G6), 3.917/2.040, 4.167/2.130, 4.167/2.190. Unfortunately, the G6 version has the longest first of the entire group, so there isn't any stock GM option for a longer 1st. Your only option would be have a custom input shaft and corresponding gears on the main shafts made.

As I mentioned in the other thread, fix the shortness of 1st with the final drive swap. Even with the "wider than ideal" 1-2 upshift, you will still be within 5 lb/ft from peak torque given the super flat torque curve of the LS4.
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Report this Post11-19-2020 08:29 PM Click Here to See the Profile for WillClick Here to Email WillSend a Private Message to WillEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fieroguru:

3.091, 3.348, 3.545 (G6), 3.762, 3.895, 3.909, 4.176.


Do you know what applications actually received the 4.176?
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Report this Post11-19-2020 09:47 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
No idea...
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Report this Post11-21-2020 07:09 AM Click Here to See the Profile for Rickady88GTClick Here to Email Rickady88GTSend a Private Message to Rickady88GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
Cool thanks for the explanation.
My next question is about the noise that people have complained about from the transmission. Do you know what it is and how to fix it?
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Report this Post11-21-2020 08:02 AM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Rickady88GT:

Cool thanks for the explanation.
My next question is about the noise that people have complained about from the transmission. Do you know what it is and how to fix it?


The rattle is from the gears on the shafts rocking back and forth with engine crankshaft pulsing. Keeping the camshaft stock (smooth idle) and using a dual mass flywheel (better crankshaft pulsing dampening) will make it better.

Mine is worse than most due to the camshaft, choppy idle and the 12lb flywheel. I have experimented with lots of transmission oil combos, but the way to completely stop the rattle is to press down on the clutch when idling. As you can hear in this video, I can make it rattle less or more as well as make it stop completely with motions of the clutch pedal.
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Report this Post11-21-2020 10:48 AM Click Here to See the Profile for sourmashClick Here to Email sourmashSend a Private Message to sourmashEdit/Delete MessageReply w/QuoteDirect Link to This Post
Wow, that rattle is pronounced in the F40.

 
quote
Originally posted by fieroguru:

My first trip was 287 miles at 75 mph and averaged 28 mpg. I want to do another one at 70 mph to see if I can't get over 30 (my 29 mpg with the other wheels and tires was at 70 mph) . The 235 and 285 tires certainly are not helping the mpg. My rear tires are 24.8" tall.


Would that be a 285/35-17?
I'm quoting this in order to save searching time, and since it's a pretty important factor in the overall outcome. And because it's a possible work around to the trans gearing issue, or will there be not be enough wiggle to perform an adequate and practical change in tire height? Does a 28" tire bring the effective ratio down to similar to using a 3.09 final drive?

[This message has been edited by sourmash (edited 11-21-2020).]

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Report this Post11-21-2020 11:34 AM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by sourmash:

Wow, that rattle is pronounced in the F40.


Would that be a 285/35-17?
I'm quoting this in order to save searching time, and since it's a pretty important factor in the overall outcome. And because it's a possible work around to the trans gearing issue, or will there be not be enough wiggle to perform an adequate and practical change in tire height? Does a 28" tire bring the effective ratio down to similar to using a 3.09 final drive?



Like I said earlier, my car is worse based on the choppy idle, 12 lb flywheel and I was intentionally making it rattle as hard as I could to show the different result in release technique. Don't assume every F40 sounds like mine, because they don't.

I run 285/30/18... on 9.5" wide rear wheels. On the 88s' you have to go to 18s for this width to clear the top of the knuckle attachment to the strut.

3.09 is a 13% reduction in final drive ratio. To get the same result with a diameter change, you would need tires 13% taller, which would be a 28" tall tire. If all you are looking at is cruise rpm, then this will work, but there are 5 pretty significant drawbacks to this method.

1. Increased wheel/tire combo weight will have an impact on acceleration beyond just the effective ratio change.
2. Sidewall flex from the taller tire/sidewall will make the cornering sloppy. Fix by running 20s and we go back to issue #1.
3. Reduces effectiveness of brakes. Contact patch is now 11% further from the wheel center which reduces the mechanical advantage of the brake calipers to stop the car. Fix with larger rotors which takes you back to #1.
4. Increased lateral loading on wheel bearings. Contact patch is 11% further from bearing center, so same lateral load induces an 11% larger bending moment on the wheel bearing flange as well as the bearing itself. This might be OK on a cruiser, but this would be a very bad idea for those that autocross and track the car as the bearings and flanges already have a shortened life.
5. Tire clearance reducing available suspension travel. With my 24.8" tires and current stance (about 1.5" lower than stock), I have barely kissed the wheel well liner. Making the tires radius 1.6" larger will limit available suspension travel and ride quality unless your goal is to have an off-road stance.

[This message has been edited by fieroguru (edited 11-21-2020).]

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Report this Post11-21-2020 05:12 PM Click Here to See the Profile for sourmashClick Here to Email sourmashSend a Private Message to sourmashEdit/Delete MessageReply w/QuoteDirect Link to This Post
I think I'd be ok experimenting with tire sizes from about 26 to 27 inches for the cost differential. No, it's not an equivalent method. But it's as I said, a work around that someone might find beneficial to their cause. Importing a used F40 has risks, like getting an abused one.

I've had another car make with a nearly terrible 1st gear that had less ability to mess with tire sizing. Having to chase that Mustang GT down in 3rd could've been avoidable with an ability to change the final drive. I think they devised that ability later.

ADDED to avoid another post that nobody else might be interested in: I went back to see that Charlie64's wide body ran a rear Forgeline SP3P 19x11 with a 325/30-19 which was about 26.7" wheel. To me the car had too tall of a gear for the torque, but perhaps it was the unsprung weight? He posed that the wheel might weigh 27 lbs or so.

[This message has been edited by sourmash (edited 11-21-2020).]

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Report this Post11-21-2020 08:42 PM Click Here to See the Profile for Rickady88GTClick Here to Email Rickady88GTSend a Private Message to Rickady88GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fieroguru:


The rattle is from the gears on the shafts rocking back and forth with engine crankshaft pulsing. Keeping the camshaft stock (smooth idle) and using a dual mass flywheel (better crankshaft pulsing dampening) will make it better.



Ok, now I am just benchtop racing, but just how loose are the tolerances on the shaft to make that much noise? Are the gear sets just floating on splines with crude snap rings holding them in a "general" location? If the same noise exists at operating temperature, then it goes without saying it isn't for expansion. Is there no fix? I assume that this noise will not decrease the life of the transmission? Will it get worse with time?
And the question that everyone has asked, why would a manufacturer produce a product that sounds like it is already wore out?
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Report this Post11-21-2020 09:50 PM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Rickady88GT:
...
And the question that everyone has asked, why would a manufacturer produce a product that sounds like it is already wore out?


Just my $.02.

This is not exactly a stock installation. No GM product with the F40 has a lumpy cam, like Paul's.
Also, GM went to considerable expense to develop the dual mass flywheel that is normally supplied with this trans, with the 3.9 in the G6.
Paul's installation has a more conventional flywheel/clutch setup.
These are both conditions that this trans is normally not ever subjected to.
When we mod our cars, we have to accept and understand the compromises that happen, when we "re-engineer" an installation, to suit a specific purpose.

Edit - removed a bunch of pointless babble...

[This message has been edited by Raydar (edited 11-21-2020).]

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Report this Post11-21-2020 10:07 PM Click Here to See the Profile for Rickady88GTClick Here to Email Rickady88GTSend a Private Message to Rickady88GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Raydar:


Just my $.02.

This is not exactly a stock installation. No GM product with the F40 has a lumpy cam, like Paul's.
Also, GM went to considerable expense to develop the dual mass flywheel that is normally supplied with this trans, with the 3.9 in the G6.
Paul's installation has a more conventional flywheel/clutch setup.
These are both conditions that this trans is normally not ever subjected to.
When we mod our cars, we have to accept and understand the compromises that happen, when we "re-engineer" an installation, to suit a specific purpose.

Edit - removed a bunch of pointless babble...



With a conventional clutch and flywheel, how much room is in the bell?
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Report this Post11-21-2020 10:45 PM Click Here to See the Profile for LarryinkcSend a Private Message to LarryinkcEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fieroguru:


The rattle is from the gears on the shafts rocking back and forth with engine crankshaft pulsing. Keeping the camshaft stock (smooth idle) and using a dual mass flywheel (better crankshaft pulsing dampening) will make it better.

Mine is worse than most due to the camshaft, choppy idle and the 12lb flywheel. I have experimented with lots of transmission oil combos, but the way to completely stop the rattle is to press down on the clutch when idling. As you can hear in this video, I can make it rattle less or more as well as make it stop completely with motions of the clutch pedal.


I don't know if this would work in an F40 but it really helped with my gear rattle. I have a 3800 swap with a light flywheel in front of the Getrag 5 speed and it has the same annoying rattle at idle, kind of embarrassing sitting at stoplights in traffic. I worked my way through all the Red Line GL 4 gear oils, each one made a slight difference but even the with the 75W140 the rattle persisted. Against a Red Line tech's advice I put Heavy Shockproof in it and most of the rattle is gone and it actually shifts a bit better. I don't drive it in the winter but have driven it a couple of times with temps in the low 30s and it was a little bit stiffer, but not bad, until it warmed up. I only have about 1000 miles with the Shockproof and all is good so far, my research found that some Bimmer guys are running it for the same issue.

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Report this Post11-22-2020 02:20 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by sourmash:
ADDED to avoid another post that nobody else might be interested in: I went back to see that Charlie64's wide body ran a rear Forgeline SP3P 19x11 with a 325/30-19 which was about 26.7" wheel. To me the car had too tall of a gear for the torque, but perhaps it was the unsprung weight? He posed that the wheel might weigh 27 lbs or so.


His car is great, but it has large heavy wheels front/rear, heavy brakes, heavier body kit, heavy stereo with amps, aftermarket dash and door panels, aftermarket suspension, 3800 sc with intercooler, etc... The car probably tips the scales at 3400 to 3500 lbs without driver. I think your torque vs. acceleration was skewed by more than just the tallness of the tires.

My car tipped the scales at 2807 at the 30th and all my current round of upgrades there is a large focus on weight reduction to offset the weight of the turbo.


 
quote
Originally posted by Rickady88GT:
Ok, now I am just benchtop racing, but just how loose are the tolerances on the shaft to make that much noise? Are the gear sets just floating on splines with crude snap rings holding them in a "general" location? If the same noise exists at operating temperature, then it goes without saying it isn't for expansion. Is there no fix? I assume that this noise will not decrease the life of the transmission? Will it get worse with time?
And the question that everyone has asked, why would a manufacturer produce a product that sounds like it is already wore out?


The slop isn't between the gears and shafts, it is between the teeth of the meshed gears. I think the other factor is that the upper main shaft sits well above the oil level and none of the gears are submerged which would help reduce rattling. GM issues a TSB to reduce the oil level to that shown below (based on the discoloration of the case) they dropped it by about 1/3 in an effort to reduce the slight rattle (nothing like what my car has).


GM designed it to work with a super smooth idle and a 30+ lb dual mass flywheel. Even then it wasn't whisper quiet. But I wanted a choppy idle, light weight flywheels which causes significant oscillations in the crankshaft rotation at idle, which is why mine it probably one of the worst.

The fix is push the clutch pedal when stopped. That stops all movement inside the transmission and stops the rattle (as the video above shows).

The rattling to some degree is common with lots of manual transmission across several manufacturers, but it doesn't impact service life.


 
quote
Originally posted by Raydar:
Just my $.02.


All true.
Even with the rattle, I would do everything exactly the same way again. I am very satisfied with all the benefits of the F40, and just keep the clutch pedal pushed or slowly let out the clutch pedal when I am going to allow it to rattle.


 
quote
Originally posted by Rickady88GT:
With a conventional clutch and flywheel, how much room is in the bell?


The F40 bellhousing is 1" deeper than the Fiero getrag, but the input shaft is about the same length. This means that w/o the dual mass setup, you still have to have a thick flywheel to put the clutch disk in the proper place to fully mesh with the input shaft. While my flywheel is only 12 lbs, it is 1 5/8" thick to take up the space of the dual mass flywheel.

 
quote
Originally posted by Larryinkc:
I don't know if this would work in an F40 but it really helped with my gear rattle. I have a 3800 swap with a light flywheel in front of the Getrag 5 speed and it has the same annoying rattle at idle, kind of embarrassing sitting at stoplights in traffic. I worked my way through all the Red Line GL 4 gear oils, each one made a slight difference but even the with the 75W140 the rattle persisted. Against a Red Line tech's advice I put Heavy Shockproof in it and most of the rattle is gone and it actually shifts a bit better. I don't drive it in the winter but have driven it a couple of times with temps in the low 30s and it was a little bit stiffer, but not bad, until it warmed up. I only have about 1000 miles with the Shockproof and all is good so far, my research found that some Bimmer guys are running it for the same issue.


In the 6 years I have driven the F40, I have tried most of the various fluid recommendations from the Saab forums and other references to transmission rattling. I am using a 50/50 mix of redline MT-90 and one of their higher viscosity fluids. Didn't really see much benefit on my setup, but I don't want to go any thicker as it already made cold startup shifts noticeably harder.
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Report this Post11-22-2020 04:52 PM Click Here to See the Profile for LarryinkcSend a Private Message to LarryinkcEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fieroguru:


In the 6 years I have driven the F40, I have tried most of the various fluid recommendations from the Saab forums and other references to transmission rattling. I am using a 50/50 mix of redline MT-90 and one of their higher viscosity fluids. Didn't really see much benefit on my setup, but I don't want to go any thicker as it already made cold startup shifts noticeably harder.


I probably should have tried the Lightweight Shockproof first, but I didn't want to toss any more expensive gear oil out. I may give the Lightweight a try, a seller on ebay has a gallon for $62.00.

Red Line info:

Lightweight Shockproof "Film thickness greater than an SAE 75W140, yet low fluid friction like 80W gear oil or 30W motor oil - Excellent low-temp flow, improved cold shifting"

Heavy Shockproof "Film thickness greater than an SAE 75W250, yet low fluid friction like 75W90"

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Report this Post11-22-2020 05:54 PM Click Here to See the Profile for Rickady88GTClick Here to Email Rickady88GTSend a Private Message to Rickady88GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
So the noise is in neutral and the clutch out?
No noise in gear with clutch in?
Does it stop just by putting it in gear, or is it only clutch manipulation?
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Report this Post11-22-2020 06:36 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Rickady88GT:
So the noise is in neutral and the clutch out?


Correct. Car stopped, transmission in neutral (no gear selected), clutch pedal released, engine idling = rattle.

 
quote
Originally posted by Rickady88GT:
No noise in gear with clutch in?


Correct. Clutch pedal pressed = no rattle.

 
quote
Originally posted by Rickady88GT:
Does it stop just by putting it in gear, or is it only clutch manipulation?


Pressing the clutch pedal is all it takes to stop the rattle. It stops the rattle in neutral as well as any gear you choose to select.
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Rickady88GT
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quote
Originally posted by fieroguru:


Pressing the clutch pedal is all it takes to stop the rattle. It stops the rattle in neutral as well as any gear you choose to select.


Cool thanks.
That is kinda bizarre with or without the massive dual system
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quote
Originally posted by fieroguru:
His car is great, but it has large heavy wheels front/rear, heavy brakes, heavier body kit, heavy stereo with amps, aftermarket dash and door panels, aftermarket suspension, 3800 sc with intercooler, etc... The car probably tips the scales at 3400 to 3500 lbs without driver. I think your torque vs. acceleration was skewed by more than just the tallness of the tires.


It makes me rethink ever wanting a wide body, when considering the additional weight it can add. Hadn't really thought about that.
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