Ok, Throw out everything, you've just taken the blue pill and your in neverland. What would be the ideal f40 transmission Gear Ratios for use with a V8.This is just a friendly discussion about the ratios in a perfect world. What materials would you use? and to what v8 would you attach said "perfect" transmission? I'm interested in hearing everyone input.
What V8? Ideal gear ratios are based on the engine's torque and power curves. For a standard LSx though, the gears out of the C6 Z06 6 speed would be nice, but not perfect.
What V8? Ideal gear ratios are based on the engine's torque and power curves. For a standard LSx though, the gears out of the C6 Z06 6 speed would be nice, but not perfect.
anything you want. this is a perfect world scenario. basically if it will fit into a fiero you can use it, so this excludes GIGANTIC motors because you wouldn't be using a f40 if you had a 572BB Ram Jet or a 1000CI METH motor.
Well, a small displacement V8, like in an F1/Indy/CART car, that can rev out to 15K RPM, would probably match up much better to the stock F40 ratios, than the larger V8s people are actually putting in Fieros.
There is no single set of ratios that would be perfect for all possible uses of a car though. I think the stock F40 gears are good enough for a Fiero though. I love my Fieros, but they are nowhere near being ideal super/sports cars. They are fun commuter cars, cheap and easy to mod, and great at turning heads. The Fiero body might look timeless, but underneath the skin, the Fiero is a product (victim) of its time. It just doesn't come anywhere near to the engineering, design, and technology that goes into a modern million dollar supercar. If I were going to spend a million dollars on an ideal supercar for me, even if I had everything custom built, it still wouldn't be a Fiero.
But I will be quite happy with my stock F40 gearbox mated to my LS4, when I get it done and running in the car.
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11:44 AM
fieroguru Member
Posts: 12498 From: Champaign, IL Registered: Aug 2003
The T56 has been the performance transmission for GM for years and the ratios have been revised a few times. ZO6 ratios are probably considered the best and by changing the 1st and FD of the F40 you can get very close. 3.0 first gear and a 3.15 final drive would be a very good all round performer with an engine with 250+ lb tq. In a lighter car or with more torque you may want a 3.0 final drive (pretty close 1st gear/FD match to the camaro T56 and further lowers the cruise RPM.
The T56 has been the performance transmission for GM for years and the ratios have been revised a few times. ZO6 ratios are probably considered the best and by changing the 1st and FD of the F40 you can get very close. 3.0 first gear and a 3.15 final drive would be a very good all round performer with an engine with 250+ lb tq. In a lighter car or with more torque you may want a 3.0 final drive (pretty close 1st gear/FD match to the camaro T56 and further lowers the cruise RPM.
I was kind of hoping you would chime in. I thought the f40 4th gear was 1.05 though? and .85 and .71 for 5th and sixth? so really you wouldn't change anything other than the final drive and first? interesting.
I was kind of hoping you would chime in. I thought the f40 4th gear was 1.05 though? and .85 and .71 for 5th and sixth? so really you wouldn't change anything other than the final drive and first? interesting.
The MT2 RPO is the gear ratios that fieroguru stated. The MU9 (much rarer) has the different ratios which you stated, as well as 1.37 for 3rd.
[This message has been edited by dobey (edited 09-04-2011).]
No. The MU9 replaced the MT2 in the G6 for 2007+. It still comes mated to the 3.9. The F40-MT2 was available in Saabs as well, but those are all High Feature or Ecotec. And the new Regal Turbo has a different F40 gear set, with another RPO. The trans in the Chevy Cruze is not an F40, but is an M32 (with 2 different gear sets and RPOs).
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10:06 PM
Sep 6th, 2011
blander66 Member
Posts: 285 From: Ann Arbor MI Registered: Sep 2010
The T56 has been the performance transmission for GM for years and the ratios have been revised a few times. ZO6 ratios are probably considered the best and by changing the 1st and FD of the F40 you can get very close. 3.0 first gear and a 3.15 final drive would be a very good all round performer with an engine with 250+ lb tq. In a lighter car or with more torque you may want a 3.0 final drive (pretty close 1st gear/FD match to the camaro T56 and further lowers the cruise RPM.
While these would be better than stock ratios they are still not ideal. 1st gear is still a bit tall. The ideal way to pick gear ratios is using a rim pull plot. This is what we use to pick ratios in the transmissions that i work on. I have an excel sheet that creates rim pull plots. I will play around with that a bit to show some different situations
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01:26 PM
Will Member
Posts: 14280 From: Where you least expect me Registered: Jun 2000
While these would be better than stock ratios they are still not ideal. 1st gear is still a bit tall. The ideal way to pick gear ratios is using a rim pull plot. This is what we use to pick ratios in the transmissions that i work on. I have an excel sheet that creates rim pull plots. I will play around with that a bit to show some different situations
There was a thread a while back in which (I think) Zac88GT did some optimization work with Desktop Drag to find an "ideal" set of ratios for drag racing. Those actually turned out to be nearly identical to GM's 6 speed RWD automatic gear ratios and had a large RPM drop going into second. That gearset would violate your rim pull plot rule that the traces have to cross, and yet is the fastest.
I'm posting this with the hope that it will prove helpful.
I think that to get a more accurate picture you need to factor in how the FD, (Final Drive Ratio), effects the overall gear gatio. I have expanded on Fieroguru’s chart to include the overall gear ratio listed below.
Fieroguru’s “Ideal F40” trans with a modified 1st gear and a numerically lower final drive ratio seems to yield a transmission that is pretty close to the T56 and the Z06. It would probably work well with any V8 powered Fiero and might work well with a 3800 V6 as well.
I have a few questions however. . .1) What would you have to change inside the F40 trans to get the “Ideal F40” trans? . .2) How much would it cost? . .3) Where could you get the work done?
Any feedback from any of our resident experts would be greatly appreciated. Thanks. ~ Bob
Originally posted by FieroBobo: I have a few questions however. . .1) What would you have to change inside the F40 trans to get the “Ideal F40” trans? . .2) How much would it cost? . .3) Where could you get the work done?
1) The gears and shafts would need to be replaced, along with whatever necessary hardware there is to install the new gears.
2) Enough that nobody on this forum has done it.
3) A shop that builds custom transmission ratios for professional race transmissions is where I'd go. Maybe Quaife would do it, but no idea how much they'd charge. Would be several thousand dollars, maybe even over ten thousand.
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08:27 PM
fieroguru Member
Posts: 12498 From: Champaign, IL Registered: Aug 2003
The input shaft has 1st gear integral to it, and the two output shafts have the FD gear integral to them. So you would need 3 custom shafts w/ gear and 2 additional custom gears to complete the change. Here are a couple of pics of the shafts: Input shaft: Both output shafts:
As for cost, the first set would probably be north of 25K and if there was sufficient volume then the cost would probably drop to 3-6K per transmission.
There are several companies that make custom gear sets for other various transmissions (quaife being one of them), but all of them are quite expensive.
If I could spend 3-4K to change the ratios of the F40 to my ideal set, I would... at least twice.
dobey: . .Thanks for the info. I sort of knew that it would be pricey.
Fieroguru: . .Thanks for the detailed information, especially the pics. . .I knew that it would be expensive, but I had no idea that it would be THAT EXPENSIVE !
I guess that if I do swap an F-40 trans into my ’88 GT, I’ll just have to learn to live with the less than perfect gearing of the F-40 trans. Oh well, there are worse things than that.
~ Bob ~
------------------ "Its nice to be important. Its more important to be nice."
A far cheaper method would be to get a gearset made up with just first gear, change it to around the 11.2 overall ratio. That way you are only paying for the input shaft and first driven gear, the rest of the parts could be swapped from the existing transmission.
Would make it pretty usable for the higher winding DOHC motors so they down upshift out of the powerband from 1->2 and most other pushrod v6 motors would probably do pretty well with it. The torque monster v8 motors would at least get somewhat even upshifts and a taller first gear.
[This message has been edited by brian89gp (edited 10-18-2011).]
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08:25 PM
Oct 19th, 2011
Will Member
Posts: 14280 From: Where you least expect me Registered: Jun 2000
The input shaft has 1st gear integral to it, and the two output shafts have the FD gear integral to them. So you would need 3 custom shafts w/ gear and 2 additional custom gears to complete the change.
It's been a LONG time since I looked at a diagram of the F40 internals, but there's something strange about the power flow in reverse. I don't *think* it impacted the ability to change ratios, but I may be wrong about that. In reverse, power flowed from the input shaft, to one output shaft to the other output shaft to the diff. I don't remember which gears were "shared" with the forward ratios, though.
The F23 and Getrag 284, for example, have oddball power flows in various gears that make them *EXTREMELY* difficult to re-gear.
Personally, I'd use the early MT2 6th and 3.91 final with the MU9 3rd-5th and custom 1st-2nd at 2.50 and 1.85.
The end result would be this:
code:
F40 Frankenstein Final 3.91 Shifted Split Overall First 2.5 9.77 Second 1.85 0.74 7.23 Third 1.37 0.74 5.36 Fourth 1.05 0.77 4.10 Fifth 0.85 0.81 3.32 Sixth 0.623 0.73 2.44
Spread 4.01
[This message has been edited by Will (edited 10-19-2011).]
I wonder if 1st gear from an F35 shares a similar design to the F40. Or at least, if the Quaife 6-speed conversion for the F35 shares a similar design. Then one could get this Quaife kit, and put the 1st gear in an F40, bringing first down do 3.00 instead of the insane 3.77. While not perfect, it would bring the trans very close to the gear ratios in the Z06 trans, and would only cost about $2500-3000.
I can't tell if the gear design is the same from the picture on Quaife's site, but it looks like it could maybe be a possibility.
I wonder if 1st gear from an F35 shares a similar design to the F40. Or at least, if the Quaife 6-speed conversion for the F35 shares a similar design. Then one could get this Quaife kit, and put the 1st gear in an F40, bringing first down do 3.00 instead of the insane 3.77. While not perfect, it would bring the trans very close to the gear ratios in the Z06 trans, and would only cost about $2500-3000.
I can't tell if the gear design is the same from the picture on Quaife's site, but it looks like it could maybe be a possibility.
I was talking to Quaife a little while ago about a custom gearset that just replaced first gear (input shaft and first driven gear would be the only parts in the kit). You need to either provide them with drawings or ship them a sample and pay them to create drawings. After that, they said that a production run of under 10 units would be so insanely expensive that it probably isn't worth it
Originally posted by brian89gp: I was talking to Quaife a little while ago about a custom gearset that just replaced first gear (input shaft and first driven gear would be the only parts in the kit). You need to either provide them with drawings or ship them a sample and pay them to create drawings. After that, they said that a production run of under 10 units would be so insanely expensive that it probably isn't worth it
I don't know what exactly you discussed with them, but making a new custom gear is a very different discussion than using an existing gear they already make.
I don't know what exactly you discussed with them, but making a new custom gear is a very different discussion than using an existing gear they already make.
Just the process needed to get a custom first gear for the F40. I'm going off of the assumption that one input shaft and one driven gear will be cheaper then a custom full 6 gear stack.
The F35 is a two-axis design and the F40 is a three-axis design. It is unlikely that the input shaft between the F35 and F40 are the same.
Its hard to tell with the diagrams above, but it looks like the two removable gears on the input shaft drive 3-4 on one output shaft and 5-6 on the other. This is probably why gears 3-6 changed on the MU9 version, they replaced all of the removable gears and re-used the input shaft (thus leaving the integrated 1-2 gears alone).
Originally posted by brian89gp: The F35 is a two-axis design and the F40 is a three-axis design. It is unlikely that the input shaft between the F35 and F40 are the same.
But if the inner splines for the gear to fit on the shaft, and the shaft diameter, are the same for 1st gear in the F35 as in the F40, it shouldn't matter what shaft it's on. The gear doesn't care which shaft it's on. If it does in fact fit, and Quaife can sell just the 1st gear itself at a reasonable price, I think it would be a good option for several of us going with the F40.
But if the inner splines for the gear to fit on the shaft, and the shaft diameter, are the same for 1st gear in the F35 as in the F40, it shouldn't matter what shaft it's on. The gear doesn't care which shaft it's on. If it does in fact fit, and Quaife can sell just the 1st gear itself at a reasonable price, I think it would be a good option for several of us going with the F40.
The F40 input shaft has 4 gears on it plus the idler for reverse. The stock F35 input shaft has 6 gears on it with the reverse idler gear being seperate, the Quaife 6spd F35 would have 7 gears on it.
If I'm looking at it right, the bottom two gears on the output shafts that are meshed together are for 1st and reverse. Engage one and you get first, engage the other and you get reverse. The other integrated gear on the input shaft would be second gear. Makes sense why they only changed 3-6 on the MU9 version.
[This message has been edited by brian89gp (edited 10-19-2011).]
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12:43 PM
Will Member
Posts: 14280 From: Where you least expect me Registered: Jun 2000
But if the inner splines for the gear to fit on the shaft, and the shaft diameter, are the same for 1st gear in the F35 as in the F40, it shouldn't matter what shaft it's on. The gear doesn't care which shaft it's on. If it does in fact fit, and Quaife can sell just the 1st gear itself at a reasonable price, I think it would be a good option for several of us going with the F40.
The likelihood of the gears randomly matching between two different manufactures is vanishingly small. Give it up.
There's a hell of a lot more to it than the diameter and spline count...
If I'm looking at it right, the bottom two gears on the output shafts that are meshed together are for 1st and reverse. Engage one and you get first, engage the other and you get reverse. The other integrated gear on the input shaft would be second gear. Makes sense why they only changed 3-6 on the MU9 version.
Good find. The lower two on the left shaft would be 1st and 2nd, the upper two on the left 5th and 6th. Third and fourth are the upper pair on the right shaft and reverse is the lowest gear on the right shaft. Note that reverse is the only gear shifted by that shift collar.
In order to change the first gear ratio, the reverse output gear would have to be changed as well. At that point, if you're making the custom input shaft, custom first output and custom reverse output, you might as well make the custom 2nd output too. It wouldn't be that much additional expense compared to just changing 1st. In for a penny, in for a pound.
[This message has been edited by Will (edited 10-19-2011).]
Will, two different manufacturers? The F40 and F35 are both Getrags. Sure there's more to it than diameter and splining, but those are a good place to start. And I think it's worth a simple inquiry to Quaife, who actually manufacture these custom gear sets for lots of transmissions, many of which are Getrags.
No harm in asking them if it fits, given the info is probably much more available to them, than to anyone on here. The "just give it up" attitude is not helpful, regardless of what Quaife says in the end. If I wanted to "just give it up already," I'd go get rid of all my Fieros and buy something else. Maybe a ZR-1, Lotus, Lambo, or any number of other cars that already have a better suspension, better engines, and better gearing. But instead, I'm choosing to stick around and help the Fiero community, by going ahead and asking Quaife about the fitment, and reporting the answer here when I get it.
Good find. The lower two on the left shaft would be 1st and 2nd, the upper two on the left 5th and 6th. Third and fourth are the upper pair on the right shaft and reverse is the lowest gear on the right shaft. Note that reverse is the only gear shifted by that shift collar.
In order to change the first gear ratio, the reverse output gear would have to be changed as well. At that point, if you're making the custom input shaft, custom first output and custom reverse output, you might as well make the custom 2nd output too. It wouldn't be that much additional expense compared to just changing 1st. In for a penny, in for a pound.
It looks like maybe 5th and 3rd are driven by the same gear on the input shaft. Makes the ratio between those two gears tied to each other. I'm guessing 5th and 3rd, it might be 6th and 4th or some other combo.
I rather like the stock gearing of the MU9 with a 3.06 first gear and the 0.62 6th gear from the MT2. That is why I was only bringing up the first gear change.
I am comparing of course to the Getrag 284, I drove one for years and have always thought that it had a good set of gear ratio's. Oddly enough, if you change the final drive to 4.1 of the above mentioned arrangement then 1-3 on the F40 is very very close to 1-3 on the Getrag 284. Of course the 3.55 stock FDR is probably fine for the lighter Fiero with a big engine and is actually somewhat close to the Z06 overall ratio a few posts up. 4.1 FDR would be more useful for the G6 and w-body people.
Can't argue with the penny/dollar. Other then my bank account prefers the penny method.....
quote
Originally posted by dobey:
Will, two different manufacturers? The F40 and F35 are both Getrags. Sure there's more to it than diameter and splining, but those are a good place to start. And I think it's worth a simple inquiry to Quaife, who actually manufacture these custom gear sets for lots of transmissions, many of which are Getrags.
Compare the pics of the input shaft to the parts diagram above http://www.genuinesaab.com/...039758d6d3e3125b1f05 Double shaft vs triple shaft transmission. It is highly unlikely that anything fits between the transmissions.
[This message has been edited by brian89gp (edited 10-19-2011).]
Will, or anyone else, do you know how easy it would be to make the TOB taller? If a custom input shaft is made it would be easy to specify that it be longer so that the more common then dirt stock neutral balance flywheels can be used without needing adapters/spacers/flex plates/aluminum flywheels to make up the difference for the overly thick G6 flywheel. I saw a picture on the MR2 forum of the back side of the TOB and it appears to have an integrated input shaft seal in it so a spacer on top would be preferred.
Originally posted by brian89gp: Compare the pics of the input shaft to the parts diagram above http://www.genuinesaab.com/...039758d6d3e3125b1f05 Double shaft vs triple shaft transmission. It is highly unlikely that anything fits between the transmissions.
Hrmm. So I think maybe fieroguru got the gears wrong in the above diagram he posted. According to https://www.fiero.nl/forum/Forum2/HTML/113638.html with the same diagram, 1st is entirely on the main lower shaft, and the gears on the input shaft are used with 3rd-6th gears, which are split between the two shafts. So now, I'm not sure which of those is correct.
I'm not sure which gear is actually first in the real photos on the page you linked, but from the diagrams, it looks like they could be very close if not the same, so I think it's worthwhile to pursue that question on the side until Quaife or someone with an F35 with Quaife kit, and F40, side-by-side could compare for sure. We may never get an answer, but if gear and shaft diameters, and spline count match up, it would certainly be interesting.
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05:52 PM
fieroguru Member
Posts: 12498 From: Champaign, IL Registered: Aug 2003
Originally posted by dobey: Hrmm. So I think maybe fieroguru got the gears wrong in the above diagram he posted. According to https://www.fiero.nl/forum/Forum2/HTML/113638.html with the same diagram, 1st is entirely on the main lower shaft, and the gears on the input shaft are used with 3rd-6th gears, which are split between the two shafts. So now, I'm not sure which of those is correct.
I said that 1st is integral with the input shaft, which 1 of the 2 gears that makes up 1st gear is (notice the 2 gears on the input shaft- part 108 - right behind the input splines)... those are are 1st (meshing with the lower main shaft - part 232) and reverse, meshing with the upper main shaft (part 327)... I can't confirm the order on the input shaft between 1st and reverse, but they are both cut into the input shaft.
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08:59 PM
fieroguru Member
Posts: 12498 From: Champaign, IL Registered: Aug 2003
I'm not sure which gear is actually first in the real photos on the page you linked, but from the diagrams, it looks like they could be very close if not the same, so I think it's worthwhile to pursue that question on the side until Quaife or someone with an F35 with Quaife kit, and F40, side-by-side could compare for sure. We may never get an answer, but if gear and shaft diameters, and spline count match up, it would certainly be interesting.
Here is the quaife F35 6 speed conversion shafts... notice the first couple of gears formed on the staft, they do not appear to be in the same location as the F40.
Here is the F40 one:
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09:16 PM
PFF
System Bot
Will Member
Posts: 14280 From: Where you least expect me Registered: Jun 2000
Will, two different manufacturers? The F40 and F35 are both Getrags. Sure there's more to it than diameter and splining, but those are a good place to start. And I think it's worth a simple inquiry to Quaife, who actually manufacture these custom gear sets for lots of transmissions, many of which are Getrags.
The F40 is a product of the late collaboration between Fiat and GM. It's not a Getrag. It's worth pursuing if there's a chance it'll work. In this case, there isn't. Choose your battles.
quote
Originally posted by brian89gp:
It looks like maybe 5th and 3rd are driven by the same gear on the input shaft. Makes the ratio between those two gears tied to each other. I'm guessing 5th and 3rd, it might be 6th and 4th or some other combo.
In order to change the first gear ratio, the reverse output gear would have to be changed as well.
I just had an ugly realization. In order to make first gear taller, the input gear must grow and the output gear must shrink. This means that the reverse output gear must grow to maintain mesh with the 1st output gear. It may end up interfering with the 1st input gear, or at least being a limitation on how tall 1st can go.
Originally posted by Will: The F40 is a product of the late collaboration between Fiat and GM. It's not a Getrag. It's worth pursuing if there's a chance it'll work. In this case, there isn't. Choose your battles.
It is a product of collaboration between Fiat, GM, and is designed by Getrag and was built at the Opel HQ plant in Germany. Not sure where the new ones are built now, as they were relocated last year. However, it is as much a Getrag as the Fiero "Getrag" is a Getrag, which was built by Muncie in Indiana.
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10:24 PM
Oct 20th, 2011
Will Member
Posts: 14280 From: Where you least expect me Registered: Jun 2000
It is a product of collaboration between Fiat, GM, and is designed by Getrag and was built at the Opel HQ plant in Germany. Not sure where the new ones are built now, as they were relocated last year.
Source?
There are design features in the F40 that don't look very "Getrag-like". 25 years ago when the 282 was introduced, it used sealed ball bearings to take the axial loads of the input and output shafts. This simplified production as only one pair of tapered rollers (differential) would have to be shimmed when the transmission was built. The F40 uses tapered roller pairs on all shafts. For Getrag, the tapered rollers would be step backward in design and manufacturing philosophy.
[This message has been edited by Will (edited 10-24-2011).]
