So I was wondering. i know many guys gere use the F40 6Spd trans. What is the highest horsepower and TQ anyone is currently putting through one of these trans?
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06:46 PM
PFF
System Bot
gtxbullet Member
Posts: 4180 From: Pewaukee, Wisconsin, USA Registered: Apr 2008
mainly V-8's,but there have been a couple 3800 Supercharged conversions as well.
as far as actual horse power, I know it can handle up to 300 crank horse power without any issues. but only if you drive normally (not beat the living crap out of it) and once in a while really get on it.
Personally from the destroyed F-40's I've seen pictures of I'd say anything under 300 and you should have years of use.
only down side is NO PARTS AVAILABLE. if it fails you need to buy a new one. and since they are only $300-450 online (BRAND NEW) it would be worth it the buy two of them. especially if you plan on owning the car or the engine swap you're thinking of for more than a couple years.
Everyone will have their own fact and opinions. learn everything you can before you make a choice. and when you do make the choice YOU WANT
[This message has been edited by gtxbullet (edited 02-22-2013).]
I'm pretty sure Troyboy's Fiero is running a cryo treated F40... As far as raw numbers, Troy's supercharged LS7 is pushing 540 ft-lbs at the wheels, last I heard. I wouldn't expect it to last forever if beat daily, though.
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07:37 PM
Archie Member
Posts: 9436 From: Las Vegas, NV Registered: Dec 1999
Ok. I am working on building a supercharged LQ4. ill be around 500HP easy. didnt know if the f40 could take it or if i needed to look at diff options.... Was there a Porche trans used somewhere with the longetudenal (sp) set up??? I wonder how much power they can take... :-/
I sent the pictures to a Saab tranny builder with only a description of my motor and he told me without a hint that I was running a solid flywheel and clutch disc and stated the tranny failure appeared to be fatigue related. His suggestion to offset the stress was a flywheel at least 17 lbs or more in weight and a sprung clutch hub. Although I used syncromesh instead of the specified gear oil and the tranny was from a wrecked vehicle, I believe the motor just overwhelmed it. Just by the Gtech module runs I've made I know the motor at the time was turning right at 400 lb/ft with the camshaft fully advanced favoring bottom end torque along with high compression, the launch was phenomenal. Now with the camshaft degreed in and the compression lower by .5 points the takeoff is not as aggressive as before and the acceleration comes on strong and smoother after the car gets moving. The pictures above look like there may have been some clutch dumping or, wheel hopping going on in that particular failure.
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08:56 PM
FFIEROFRED Member
Posts: 751 From: GULFPORT, MS Registered: May 2008
Ok. I am working on building a supercharged LQ4. ill be around 500HP easy. didnt know if the f40 could take it or if i needed to look at diff options.... Was there a Porche trans used somewhere with the longetudenal (sp) set up??? I wonder how much power they can take... :-/
Ignore the HP numbers. Torque curve, shifting style (how you drive it), and the shock loading as a result of those two, are what matter. There are plenty of LS376/480 swaps running around mated to the F40 trans, which haven't had any issues. If you're really worried about it, there are plenty of things you can do to help.
1) Like Joseph said, the flysheel/clutch combination will be a point of issue. With the LQ4 and need for an adapter plate, it will likely be less of an issue though, as the spacer/flywheel should be pretty hefty.
2) Get the trans cryo treated. This will harden the gears a bit, but make them more brittle in the event that there is internal damage to the trans.
3) Go with a smaller engine like the 4.8 instead of the LQ4. This will lower the rotating mass of the engine a little, but also change the dynamics of the torque curve to be more suitable for the trans. It also increases reliability for going into higher RPMs, by having the shortest stroke of the LSx series V8s, allowing for higher piston speeds.
4) Avoid dumping the clutch, and shifting into or at, peak torque or HP. You kind of need to know what the torque and power curves are like for the latter of course, but these activities increase shock loading on the drivetrain, and thus increase wear, and the possibility of critical failure. That doesn't mean no spirited driving, but driving it like a race car everywhere will basically destroy any trans that isn't built for racing.
5) Depending on tuning, you may want to go turbo or N/A instead of with a supercharger. The LSx series engines are very easy to get lots of power out of. With a turbo, it may be easier to tune your engine in with lag, so that normal street driving produces less power, and you only get the power increase from 4000-6000 RPM, or such.
I'm not sure why you chose the LQ4, or supercharger, or what your exact goals with the build are, but there are plenty of options for building a reliable V8 Fiero, with plenty of power, using the LSx engines.
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08:37 AM
GT86FASTBACK Member
Posts: 757 From: Monroeville, PA Registered: Jul 2009
I got a great deal on the engine itself. i will be running alum heads and a full LS2 setup on it. I guess the only LQ4 part i will have is the Cast iron block. everyone seems to want it because they take amazing amount of abuse with very little issues. In a word, i will have an LSx engine just with an iron block under it. :-) I want something that will run good, sound great, and has that general WOW factor i guess. LoL Alot of my friends have ls powered cars and can get me alot of the parts i need.
I got a great deal on the engine itself. i will be running alum heads and a full LS2 setup on it. I guess the only LQ4 part i will have is the Cast iron block. everyone seems to want it because they take amazing amount of abuse with very little issues. In a word, i will have an LSx engine just with an iron block under it. :-) I want something that will run good, sound great, and has that general WOW factor i guess. LoL Alot of my friends have ls powered cars and can get me alot of the parts i need.
If you're going to swap the heads, I wouldn't bother with the 243/LS2 stuff unless you're getting the parts incredibly cheap compared to the L92 style heads. The Gen IV rectangle port heads are much better flowing. The LS2 stuff will work, but there are better heads and intake to swap to if you're swapping out anyway.
Here is an ebook on manual transmission building that states when replacing a dualmass flywheel with a solid flywheel be sure to install a sprung hub clutch to dampen the effect of the engine pulses or else damage to bearings or gears can result, page 44. It has other good info in it as well and is worth reviewing. Maybe the torque rating of the F40 is a function of the dualmass flywheel dampening effect in addition to the gearbox capacity and is actually reduced without it.
If you're going to swap the heads, I wouldn't bother with the 243/LS2 stuff unless you're getting the parts incredibly cheap compared to the L92 style heads. The Gen IV rectangle port heads are much better flowing. The LS2 stuff will work, but there are better heads and intake to swap to if you're swapping out anyway.
I wanted to run rectangular ports over cathedral because of the flow numbers. just a matter of money thats all. im still shopping for those. lol
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07:43 PM
Feb 25th, 2013
Will Member
Posts: 14275 From: Where you least expect me Registered: Jun 2000
Here is an ebook on manual transmission building that states when replacing a dualmass flywheel with a solid flywheel be sure to install a sprung hub clutch to dampen the effect of the engine pulses or else damage to bearings or gears can result, page 44. It has other good info in it as well and is worth reviewing. Maybe the torque rating of the F40 is a function of the dualmass flywheel dampening effect in addition to the gearbox capacity and is actually reduced without it.
Not sure about the F40, but for BMW transmissions, the dual mass or sprung hubs are ONLY for reducing gear rattle in neutral with the clutch applied. They have nothing to do with the capacity of the transmission to handle abuse. The F40's dual mass setup may have a torque limiting feature, but I don't see that as being reasonable. The heavier flywheel makes the transmission MORE likely to have a failure because the extra mass makes it easier to dramatically increase transient loading during shifts.
It definitely reduces idle noise in the F40 and according to a Sachs rep I contacted years ago has a torque limit of about 10% above the engine output. The flywheel weighs about 25 lbs by itself and somewhere in the area of 40 lbs as an assembly. That book mentions one of the production cars having a safety built into either the clutch slave, or master cylinder that limits how quickly you can dump the clutch by having a slow bleed down design that forces some clutch slipping during aggressive shifting whether you want it or not. I understand that not all dualmass flywheels are torque limited and that the Supra is one example. Whatever the case, that's the area the Saab mech said to focus protection of the F40 and he runs in excess of 400 hp in his Saab although I'm not sure of the torque load, or what type of flywheel he's using.
