Automatic Transmissions

[ggl205]

I am looking at a 4L80E with a McLeod performance kit to take 1000 horsepower. Anybody use one of these four speed automatics?

John

[kiwi belly tank]

Yep! Stuck a "used" one on that back of a twin turbo LLY Duramax 800hp/ 1480ft-lbs in a street rod / drag truck. Drove it to Oklahoma, ran Drag week, never missed a beat. 15k miles & lots of drag strips later it's still going strong with the only change being a Hughes converter more suited to the diesel. It had about 125K on it in a 3500 van before it went on the Duramax. I call that $300 worth of bullet proof.
  Sid.

[ggl205]

Now that?s the kind of recommendation I like to hear. Thanks, Sid.

John

[kiwi belly tank]

If you need a super short one, use a 4WD trans & put a short TH400 2WD housing on it. The output shaft is 32 spline (TH400) so any yoke or Greek Coupler will fit it.
You can full manual them without an ECM or aftermarket controler by hooking up micro switches on the shifter to power the appropriate solenoids so they basically become half mechanical / half electric
& you can shift them like a manual 400 with an extra hole then add a converter switch. Without governor pressure modulation they shift firm but not harsh like somebody rear ended you.
  Sid. Kiwi Skunk Works, still doing more with less.    
 

[ggl205]

Sid, this is sounding better all the time. One of my concerns was adding significantly more length to the car using an automatic but you just answered that question too. Thanks again for all the valuable and helpful information.

John

[ggl205]

OK, now that we are on the subject, what about the GM 6L90E automatic? Looks like a reasonably tidy package and two more gears. Can it be moded like the 4L80E?

Gear ratios don?t look bad either. Two overdrives.

Gear Ratios
First:   4.030
Second:   2.360
Third:   1.530
Fourth:   1.150
Fifth:   0.850
Sixth:   0.670
Reverse:   3.060

John

[ggl205]

What makes all this work is if there is an adapter to mate up either a 4L80E or 6L90E trans to my Toyota 2JZ engine. This is a long shot but has anyone done this?

John

[4-barrel Mike]

Something like https://www.atfspeed.com/2jz-adapter-plate-for-chevy-trans-w-billet-sfi-flywheel-kit.html??

Mike

[ggl205]

Mike, that is EXACTLY what I will need! Stainless said he thought someone here would have a solution to this problem. He was right. Thanks, man, big help.

Sent an e-Mail to ATF (no, not THAT ATF) to see if their adapter fits either the 4L or 6L trans. There are a couple other companies selling adapter plates too but not as complete as ATF

John

[kiwi belly tank]

I don't know anything about a 6 speed other than having one in my truck & it's longer than the 4L80.
An overdrive will cost you power & somebody smarter than me could probably tell you how much that would be & then X2 but why do you need 2?
How much wheel rpm do you need to go where you want to?
  Sid.

[ggl205]

Not quite sure about rear wheel RPM at this point, Sid. I plan on running several simulations with available final drives and tire diameters. Some of it has to do with gear splits and power required to pull them. Something of a guess on engine power data as it has not yet been on a dyno.

I have been asked to take a look at a Corvette C6 six speed (6L80E) with final drive attached (2.56). This certainly makes overall length shorter. Surprisingly, these are reasonably priced units.

John

[Stan Back]

I'm no trans-student (or trans-anything else) but it appears to me that often with overdrive trans, the jump to the final gear is often bigger percentage-wise than the steps between most of the lower ratios' changes.  This is just where you don't want it.  Depending on what you can get for final rear end ratios, you need to make that jump the smallest -- or, even better, make it straight-thru if your differential will allow it.  I guess that just depends on tire size and target speed.  We were a slowpoke trying to pull a 3.00 gear straight thru.

[ggl205]

Stan, you are correct about an overdrive drive trans gear being hard for an engine to pull but as you also said, it all depends on what final drive diff ratio you have and rear tire diameter. But I don?t have to use all gears. One of the reasons I am looking at the 8L90E 8-speed. Sixth gear is 1:00 and the other five gears are more closely spaced. A 4.56 first gear would allow me to drive away from the line without a push truck. It all might not be the best from a power loss standpoint but if all the aero numbers are correct, I will have far more power than needed to make record speed, maybe enough to challenge the 300 mph mark. At least that is the hope.

John

[Lemming Motors]

John; that is an inline 6 with a 6 or 8 speed auto up its ? What are you building, I appear to have missed some vital intel along the way.

[ggl205]

John, I ended up with a turbocharged Toyota 2JZ engine slated for a streamliner that was never built. The engine just sat until the shop changed hands and the new owner wanted all legacy crap gone. Although not dyno tuned, it should produce around 1000 HP hence, the auto six-speed transmission. I have a five-speed Indy car box with adapter bell housing but that trans may not be best suited for my car.

My lakester is still a G class car and may very well remain such. I am just exploring possibilities to use the 2JZ at some future date. The 2 liter engine I currently have is not mine and will eventually have to go back to its owner.

John