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55mph = 2600 rpm? by railshot
Started on: 04-28-2017 08:35 PM
Replies: 12 (480 views)
Last post by: JohnWPB on 05-02-2017 06:33 PM
railshot
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Report this Post04-28-2017 08:35 PM Click Here to See the Profile for railshotClick Here to visit railshot's HomePageClick Here to Email railshotSend a Private Message to railshotEdit/Delete MessageReply w/QuoteDirect Link to This Post
'88 TH125.
Opinions?
Sounds about right from all my searching.

Just curious as my other '88 GT has been modified with a different gear ratio for higher mpg and I have only had manuals until now.
The T-top hits maybe 2500 rpm @ 70 mph.

Thanks,
Dave
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Report this Post04-28-2017 11:29 PM Click Here to See the Profile for pmbrunelleClick Here to Email pmbrunelleSend a Private Message to pmbrunelleEdit/Delete MessageReply w/QuoteDirect Link to This Post
Old tachometers lie... so I would only bother trying to estimate gear ratio once the tach is calibrated, or verified with a scan tool.

Pretty sure most <<is it normal that my Fiero runs XX RPM at YY MPH>> threads would be resolved once people calibrated their tachometers.

Or the threads where people don't think the early V6s have rev limiters; probably fooled by inaccurate tachs.

If I were you, I would pay attention during acceleration to see if the torque converter lockup clutch engages or not. If you get that extra "shift", then all is working well, and no need to worry about the car.
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mrfiero
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Report this Post04-28-2017 11:57 PM Click Here to See the Profile for mrfieroClick Here to Email mrfieroSend a Private Message to mrfieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
Stock '88 GT automatics have a 3.33 final drive ratio. That makes for some pretty high RPM's on the highway. On my trip up to you I was running 3500 RPM's at around 75 MPH. It has been years since I've driven an automatic Fiero, but from what I remember from my first GT that is about right. It's nothing like my 5-speed GT at that speed.

How's the TCC treating you??
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railshot
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Report this Post04-29-2017 07:20 AM Click Here to See the Profile for railshotClick Here to visit railshot's HomePageClick Here to Email railshotSend a Private Message to railshotEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by mrfiero:

Stock '88 GT automatics have a 3.33 final drive ratio. That makes for some pretty high RPM's on the highway. On my trip up to you I was running 3500 RPM's at around 75 MPH. It has been years since I've driven an automatic Fiero, but from what I remember from my first GT that is about right. It's nothing like my 5-speed GT at that speed.

How's the TCC treating you??


TCC is plugged back in and behaving nicely!
Just in case, I have that, the 3rd gear switch, and gasket on it's way, but won't be replacing it unless it acts up like it did for you..

3500 is about what I was expecting at 75 mph, and from all my reading here it seems that 2600 rpm is the "sweet spot" for the engine due to speed limits being 55 back then.

She sure does run and sound nice!
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railshot
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Report this Post04-29-2017 07:24 AM Click Here to See the Profile for railshotClick Here to visit railshot's HomePageClick Here to Email railshotSend a Private Message to railshotEdit/Delete MessageReply w/QuoteDirect Link to This Post

railshot

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Member since Jul 2006
 
quote
Originally posted by pmbrunelle:

Old tachometers lie... so I would only bother trying to estimate gear ratio once the tach is calibrated, or verified with a scan tool.

Pretty sure most <<is it normal that my Fiero runs XX RPM at YY MPH>> threads would be resolved once people calibrated their tachometers.

Or the threads where people don't think the early V6s have rev limiters; probably fooled by inaccurate tachs.

If I were you, I would pay attention during acceleration to see if the torque converter lockup clutch engages or not. If you get that extra "shift", then all is working well, and no need to worry about the car.


Really appreciate the input.
I am getting the TCC kicking in, but was just wondering what others were seeing.

Tach is quite accurate actually, so I am confident all is well.....
I have all the old school stuff to check it, but now need to get busy and get my laptop set up for monitoring.
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Blacktree
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Report this Post04-29-2017 11:56 AM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
That does seem about right. Now you know why the 4-speed automatic swap is so popular.
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railshot
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Report this Post04-29-2017 12:04 PM Click Here to See the Profile for railshotClick Here to visit railshot's HomePageClick Here to Email railshotSend a Private Message to railshotEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Blacktree:

That does seem about right. Now you know why the 4-speed automatic swap is so popular.


That is in the back of my mind for the T-top.
I love the top end gearing with the gears in it now, but it sure is a dog off the line...
My HHR gets up to speed faster than the T does. lol
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Dennis LaGrua
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Report this Post04-29-2017 01:27 PM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaEdit/Delete MessageReply w/QuoteDirect Link to This Post
I will agree with the numbers being posted here as my 3.4L /auto is also roaring away at over 3500 RPM at highway speed. The Fiero really needs a 4 speed auto. With the 3 speed it may have more bottom end acceleration but the gas mileage for even a 2.8L in a 2700 lb car isn't real good.

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

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olejoedad
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Report this Post04-29-2017 05:56 PM Click Here to See the Profile for olejoedadClick Here to Email olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
The 125 and 4t60 have the same ratios in 1, 2 and 3, the 4t60 gets the OD 4th.
With a 3.33 final in the 4t60, it should feel the same, but with a big drop in rpm when it goes to 4th.
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randye
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Report this Post04-29-2017 06:29 PM Click Here to See the Profile for randyeClick Here to visit randye's HomePageSend a Private Message to randyeEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by olejoedad:

The 125 and 4t60 have the same ratios in 1, 2 and 3, the 4t60 gets the OD 4th.
With a 3.33 final in the 4t60, it should feel the same, but with a big drop in rpm when it goes to 4th.


It is precisely for that reason that I am so disappointed in my 3.4 swap.
I should have swapped out the T125 for the 4T60 at the same time I did the engine.
The car has nice low end torque and is ok for running around town locally but it simply isn't a "highway cruiser".
That 4th gear O.D. would have made all the difference to me.

I wish I had known you were in town and that you met up with Wade.
We could have possibly had lunch.

[This message has been edited by randye (edited 04-29-2017).]

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JohnWPB
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Report this Post04-30-2017 10:31 PM Click Here to See the Profile for JohnWPBClick Here to visit JohnWPB's HomePageSend a Private Message to JohnWPBEdit/Delete MessageReply w/QuoteDirect Link to This Post
Yep! When I drove my 2.8 Auto to Daytona a couple years ago, I felt like I was in "Passing gear" most of the time LOL! I was crusising about 75MPH most of the way. I had such a headache from that 5 hours of engine drone........

Will be taking the 3800 swap out hopefully in the next week or so for the first time. I am in the hopes the over drive, coupled with all the sound dampening I did will be much quieter.
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randye
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Report this Post05-02-2017 02:58 PM Click Here to See the Profile for randyeClick Here to visit randye's HomePageSend a Private Message to randyeEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by JohnWPB:

Yep! When I drove my 2.8 Auto to Daytona a couple years ago, I felt like I was in "Passing gear" most of the time LOL! I was crusising about 75MPH most of the way. I had such a headache from that 5 hours of engine drone........

Will be taking the 3800 swap out hopefully in the next week or so for the first time. I am in the hopes the over drive, coupled with all the sound dampening I did will be much quieter.


3800 engines tend to be very "buzzy" without a good exhaust system and proper muffler.
Lower RPMs and insulation are obviously an excellent start though.

[This message has been edited by randye (edited 05-02-2017).]

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JohnWPB
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Report this Post05-02-2017 06:33 PM Click Here to See the Profile for JohnWPBClick Here to visit JohnWPB's HomePageSend a Private Message to JohnWPBEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by randye:


3800 engines tend to be very "buzzy" without a good exhaust system and proper muffler.
Lower RPMs and insulation are obviously an excellent start though.



I will hopefully know by the end of the week what its going to sound like It is in the shop getting the final touches. To reduce as much noise as I could, I insulated the firewall, inside and out, as well as went with a stock muffler -vs- performance, and lastly I wrapped the muffler and down pipes.
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