F40 with 3800 SC question (Page 1/1)
cam-a-lot OCT 04, 03:50 PM
Hello

I have a 3800SC with some mods, mated to a 1990 Cavalier Getrag. Trans and clutch works fine

With that said, I enjoy being paranoid and always planning for the worst.. so I have been trying to find a spare 92-94 Getrag tranny, but no luck

So I am thining of biting the bullet and try to find an F40 and get the correct brackets, etc, so when the tranny does blow up, I will have something stronger to replace it with.

Can someone who has driven the F40 chime in and let me know how the gearing is compared to the factory Getrag? Is first gear more "useful"? How does it rev in 6th gear on the highway? Does it "feel" like a better trans for this engine in terms of gear ratios and overall feel?

I think I need custom axles too?

thanks

Peter
mptighe OCT 04, 04:40 PM
F23 is a better choice. The F40 chatters, and is WAY more expensive to use. I understand there is a version that doesn't need an adapter now, which is good. That said, I spent $1,700 on just the axles for mine (V8 Archie), and there were other issues. F23 is way easier, and will hold the power just fine. That's my $.02, from someone who had an F40 mated to a turbo 3800. I can direct you to a place that has brand new 2008 Cobalt F23's for $450 ish if you want to rebuild yours.

[This message has been edited by mptighe (edited 10-04-2019).]

cam-a-lot OCT 04, 10:37 PM
I had an F23 on another 3800 Fiero. Worked fine except I hated the gearing. It was out of a Cavalier- can't remember the year. First gear was useless. If memory serves me well, you could swap parts from a Cobalt SS to get a more favourable ratio?
mptighe OCT 04, 11:08 PM
Yep. I pm’d you a link to the place that had the new ones out of a cobalt. Not the most economical gearing but not the worst of the options.
fieroguru OCT 05, 12:09 PM
If you want first gear to be more usable and get the car going faster per engine RPM, then you want to look at the Launch Ratio (or starting line ratio). That is 1st gear ratio multiplied by the final drive in the differential. Tire diameter also comes into play, but for your purpose, we will assume you want to keep your current wheels and tires.

I highlighted the Fiero Getrag 5 speed. Anything above it is an improvement to most people and anything below will not improve the feel of 1st gear. Several of the transmissions I listed as "Hybrid" where you mix and match gears and final drives between two transmissions within the same transmission family. This gives you a more well rounded transmission, but normally is 3X+ the cost (purchase 2 transmissions + labor for gear swap).


Here is the same list, but sorted by cruise RPM (top gear * final drive). Again the Fiero Getrag us highlighted to show the relative benefit. The lower the cruise rpm, the less loud the car is, the more likely you are able to stay under the drone threshold, and there is an opportunity for better fuel economy.


While the Hybrid F40 w/3.091 is definitely not cheap, it is in the top two on both lists and is what I have in my LS4/F40 combo. It is awesome and makes the car feel more like a factory late model V8 application vs. an over geared swap.
sourmash OCT 06, 11:27 AM
I drove one with an F40. No idea what the gear set was but it one was installed by someone on the site. To me the legs were too long for my liking. Never got past 3rd with any acceleration. That probably would preserve it longer than one with a higher numerical gear because it wouldn't receive the same shock loading. The wheel/tire size could be adjusted.
fieroguru OCT 06, 08:54 PM

quote
Originally posted by sourmash:

I drove one with an F40. No idea what the gear set was but it one was installed by someone on the site. To me the legs were too long for my liking. Never got past 3rd with any acceleration. That probably would preserve it longer than one with a higher numerical gear because it wouldn't receive the same shock loading. The wheel/tire size could be adjusted.



I am 99% sure it was the standard G6 gearing. The ecotec and high feature versions only have single digit completed swaps, along with gear ratio swaps.

You just need to drive faster!

With stock Fiero size wheels and shifting at 6000 3rd is good for about 93 mph with the stock G6 gearing... Push it to 7000 rpm and see 109 mph.