Coming Soon: 4L65RR Manumatic System

[Turbo67camaro]

I've decided to go with a 4L80E solution with computer control.

I'll make up some up the weight gain with an aluminum drive shaft.

The first gear won't be optimum for out of the hole performance w/ 3.42 rear, but since my motor is cammed for low end torque and will use a turbo, it won't be a slouch either. With a 6000 rpm redline, 3rd gear should go to 145 mph, so I can finish the 1/4 before needing 4th.

Added bonus: the 2.48 1st might keep my wife from snapping the rear end !

For autocross and road racing, the 2.48 1st gear with 3.42 rear may prove a useful combination. If I went with a 4L60E, the 3.06 1st gear w/ 3.42 rear may be too wide to be useful, especially with a turbo motor that makes power at a lower RPM.

For highway overdrive, the wider .75 OD 4th should pair well with my 3.42 rear. With an EFI motor cammed for low RPM torque, I may sacrifice gas mileage slightly and unnecessarily compared to the .70 or .67 ratio of other trannys, but I'll get a little insurance against lugging. I should be able to plod along well at legal speed even up moderate hills. 65mph should be 1994 rpm in 4th. Maybe I'll get lucky and the RPMs will be in the sweet spot for MPG.

If money were no object, I'd get upgraded gears in the 4L80E (2.75 1st, 1.57 2nd), but I'll probably justify that money elsewhere.

Now, to figure out what torque converter and stall speed, and where to get that 4L80E.

In short, for about the same price as a really well built 700R4 or 2004R, I can get into a electronic solution. However, I get more control, more reliability, more consistency and safety at the drags, and ability to upgrade to a paddle shifter. Small price to pay for a little weight gain.

Picking a transmission has been the most difficult decision on building this car by far.



Steve, PM sent to find out what model that PCS computer is so I can research it.

Thanks for the help,

Mike

[Steve Chryssos]

I've decided to go with a 4L80E solution with computer control.
Steve, PM sent to find out what model that PCS computer is so I can research it.
Thanks for the help,
Mike

Some of these expectations will change after some installation and drive time. I'll post my experiences. Let me know down the line if you agree or disagree.

I'll make up some up the weight gain with an aluminum drive shaft.

The weight stigma is a bit overblown. We're talking about 40 lbs located at bottom middle of the car. Compared with the big gains in reliability, the weight difference is easily negated.

The first gear won't be optimum for out of the hole performance w/ 3.42 rear, but since my motor is cammed for low end torque and will use a turbo, it won't be a slouch either. With a 6000 rpm redline, 3rd gear should go to 145 mph, so I can finish the 1/4 before needing 4th.

Added bonus: the 2.48 1st might keep my wife from snapping the rear end !

You'll probably be traction limited anyway. We all are. But if that's the case, you won't snap parts.

For autocross and road racing, the 2.48 1st gear with 3.42 rear may prove a useful combination. If I went with a 4L60E, the 3.06 1st gear w/ 3.42 rear may be too wide to be useful, especially with a turbo motor that makes power at a lower RPM.

Yeah, I don't make full autocross runs in 1st gear (3.06 x 3.70). Slows the car up too much. You might get away with it. Most courses, I hit the beams in 1st, then run the rest of the course in 2nd. 3.42 gears don't work very well for autocross, so plan on airing the rear tires up.

For highway overdrive, the wider .75 OD 4th should pair well with my 3.42 rear. With an EFI motor cammed for low RPM torque, I may sacrifice gas mileage slightly and unnecessarily compared to the .70 or .67 ratio of other trannys, but I'll get a little insurance against lugging. I should be able to plod along well at legal speed even up moderate hills. 65mph should be 1994 rpm in 4th. Maybe I'll get lucky and the RPMs will be in the sweet spot for MPG.

You're right. Too many people gear their cars for excessively low cruise rpm. Modern OE transmissions are geared for one thing only: To satisfy CAFE standardized testing. If you're not careful, you'll be driving down the road at idle or close to it. We care about gas mileage also, but the pendulum between performance and economy sits closer to the middle. Give up 200-300 rpm to get the engine right at the bottom of the powerband.

If money were no object, I'd get upgraded gears in the 4L80E (2.75 1st, 1.57 2nd), but I'll probably justify that money elsewhere.

That would be slick, but in a perfect world, I would keep the 2.48 if possible and switch to 3.70 final. Remember that we have a semi viscous coupling and computer control, so gear splits are not as critical as with a manual trans. We compensate by electronically controlling shift time. Unlike a clutch, the converter absorbs most of the shock between gears. Lock up and shift time are configurable. That's not to belittle the importance of effective gear splits with respect to engine powerband--just telling you not to worry about huge, between gear rpm spikes and dips.

Now, to figure out what torque converter and stall speed, and where to get that 4L80E.
In short, for about the same price as a really well built 700R4 or 2004R, I can get into a electronic solution. However, I get more control, more reliability, more consistency and safety at the drags, and ability to upgrade to a paddle shifter. Small price to pay for a little weight gain.
Picking a transmission has been the most difficult decision on building this car by far.

You're right there as far as understanding this stuff.

[Steve Chryssos]

Thanks for all the great questions.