I've read most of the search results on the forum here, but still have some questions. Since many of the threads are over a year old, maybe there are some newer answers out there.

Lets say I'm looking for a newer transmission for my 85GT Fiero with the 3800SC already installed to a muncie 4 speed. I'd like to rule out all original fiero transmissions. With over 300ft lbs of torque (not saying I'm there, yet ) I simply don't trust them. Lets also say my goals, in order of most->least importance, are: Ability to handle more torque, less RPM drop between 3rd and 4th, lower RPMs at freeway speeds, and finally, price to adapt to my Fiero.

I've read a little about west coast Fiero's NSX transmission. Expensive... very much so, with little feedback on strength, gear ratios, and from the looks of their pictures, very hard to install. If anyone has facts or opinions here, please share them.

I've read a lot about Porsche and Audi longitudinal transmissions. Interesting, and if I were building a kit car and wasn't against a frame stretch I'd give it a shot. But I'm not, my car has already been painted and I dont have a clue how the handling would be affected.

http://www.fastfieros.com/N...nsmission_ratios.htm
lots of information there on transmissions and gear ratios. I particularly like the 6 speed F40 ratios listed for the 2005/2006 Pontiac G6, except for the very short 1st gear. Other than that, I think I'd like having this transmission. If the MPH listed at 6200 rpms are correct, I'd never hit 5th or 6th gears in a 1/4 mile. If I were drag racing, I'd be no worse off then my current 4 speed as far as shift times.

Archie sells a kit to install this transmission, which is also good. I have yet to get a price though for a 3800 swap. I already have a 4 speed shifter obviously, and it needs to be 'modified' to work with the 6 speed. Any details? Can I do it myself? If not, I'm glad to send it to archie.

Why haven't I started anything yet? FastFieros lists the F35 5 speed as 'preferred choice' for use with 3800SC and future V8 manual swaps. While I like the lower 65mph rpms that the 6 speed offers, as stated already my biggest concern is a stronger transmission. I'd go with the 5 speed if strength was a bit better than the 6.
What is different about the F35 5 speed? Will it work with archie's G6 kit? if not, what needs done to install it?
Next, which is stronger? I post the following from FastFieros:

2006 F35 5 speed
Max engine tq 200 lb-ft ( 271 Nm )
Max gearbox tq 258 lb-ft ( 350 Nm )
Gear ratios: MU3
Transmission weight: 45 kg ( 99 lb )
Maximum validated gross vehicle weight: 5071 lb ( 2300 kg )
vs
2006 F40 6 speed
Maximum engine torque: 245 lb-ft ( 333 Nm )
Maximum gearbox torque: 295 lb-ft ( 400 Nm )
Transmission weight: 56 kg ( 123.5 lb )
Maximum validated gross vehicle weight: 3527 lb ( 1600 kg )

Now I need help interpreting all this. The F40 handles more torque. The F35 is rated at less, but in a vehicle gross weight 1500lbs heavier. Do the torque ratings have anything to do with gross vehicle weight, or not? If so, which trans is stronger?

/end long post. Let the discussion begin. Thanks in advance for the help guys

I have beaten this discussion back and forth for HOURS between the "in the know" getrag guys...

Every time we come to a conclusion, we still feel that its easier to just build a 282 with a LSD. The gearing in the F23/35/40 transmissions is not worth the extra effort, and the strength is really unknown, so we dont ever see the need to gamble on it.

The F40 might be a better option for the show car, due to the gas mileage gear... but other than that, get a getrag cleaned up and consider a LSD or a 93/94 "heavy duty" diff.

The F35 seems to be a very strong trans, with an LSD option, and can be had fairly cheap... but it bolts to 1 motor, and 1 motor only.... adapter plate time if you want to put anything else on it.

[This message has been edited by darkhorizon (edited 10-23-2008).]

quote Originally posted by darkhorizon: the strength is really unknown,

GM Powertrain says the trans itself is good for 400 Nm, or 295 lb-ft. The biggest rated engine hanging off an F40 is the Pontiac variant, which produces 245 lb-ft. Saab also has an engine near this rating on an F40.

295 ft lbs is still 95 more than a Fiero trans from what I've read. weren't they only 200ft lbs? People stretched that to the 3800SC and SBC several times saying 'dont abuse it and it'll be fine'. 300 ft pounds to a 295 rated trans gives me a lot more piece of mind than 300 to a rebuilt fiero tranny, getrag or otherwise

The pain to build and convert from a 4 speed muncie to a newly built getrag 5 speed wouldn't be worth it. I can land brand new or low mileage F40s for $500 shipped, +- $100 or so. And I like the overdrive gears.

Still in 2008 no idea what abuse the F40 can take? It bolts to a 3800 from what I read... clutch/flywheel I'm a bit confused. Leaving that one to archie. Most threads saying how they were uncertain about the F40's strength were over a year old at least... and there are no "F40 failure" threads that I've seen

edit: and I posted the torque ratings already, my question between the F35 and F40 was to see if the gross vehicle weight had a factor in that rating. the F40 handles more torque, but rated for a car 1500Lbs lighter... does that matter?

[This message has been edited by zi_gravedigger (edited 10-23-2008).]

up

The F35 MU3 version with the limited slip unit is rated lower than the F40 and also has a lower gross vehicle weight at least for the 2009 GM SS models it's found in. What seems to be making the difference as far as strength is concerned is the gearing itself. The F40 in the AWD Saab has pretty much the same torque rating as before but the gross vehicle weight rating has increased by about 1000 lbs so it stands to reason that although the torque rating of the transmission is the same, it is being stress relieved for the increased load bearing capacity with gear changes. That's probably why the Fiero has been able to get away with high output engine swaps and low torque rated transmissions, weight is being traded for higher torque handling capacity.

there is another forum where all the technical data and ratings have been brought to light, swappability, as well as longevity and swaps in progress. Also located there is the swap details of the NSX trans as well as pro's and con's

------------------
Recanizin' Flat-Buns Since 2001

Eric Nelson
Internet Sales Manager
Power Ford Valencia
nelsone@autonation.com

quote Originally posted by Chicken McNizzle: there is another forum where all the technical data and ratings have been brought to light, swappability, as well as longevity and swaps in progress. Also located there is the swap details of the NSX trans as well as pro's and con's

do you happen to have a link? I'd like to read through that

Thanks for the input joseph. That makes sense I suppose