Gear box swap/upgrade in 400 auto

Dear all,

Has anybody heard of anybody doing a gearbox upgrade from the original TH400 3 speed to a TH700 4 speed gear box in a 400 series car? -Or similar?

The TH 400 is not a very nice gearbox to start with and the fact that that is only has 3 forward gears feels very outdated. A TH700 is about the same (same bolt pattern) with an overdrive to give 4 forward gears. -Or one could use the 4L60/4L80 (not the E version as it needs a computer).

-Which brings us to the most interesting bolt-on upgrade the 6L80, a six speed auto in the same casing as the 4L80 and probably a pretty straight swap to a TH400.

I know it's not original and that a manual conversion would be an alternative but it comes with lots of changes (pedals, console, mounts, clutch and so on). Not even mentioning finding a complete set (without buying a donor car).

But.....would it not be nice with a manually (paddle) shifted 6 speed in a 400?? Auto shifting for the wife go shopping and manual for me having fun…

http://www.tciauto.com/Products/6x/

Ideas?


//Robert

 

Art,

Thank you for the link. I did see them from an older thread. I think it should be even easier on the 400 since the original is a GM box mounted on a Ferrari to GM bolt pattern adapter. This means that many GM boxes would be just to bolt up.

I have seen some talking about that the tail end of the box was special for Ferrari, but I thought that this was a GM piece since they made at least three different lenghts of the drive shaft end. Can anyone please confirm if the drive shaft end on the TH400 indeed is a Ferrari made piece? Or Ferrari special order?

The idea with the 6X box is that since the bolt patterns are the same it should be more or less a straight bolt on. I understand that the mounts may be different and that the drive shaft and the torque tube may have to be shortened, but still pretty straight forward.

The neat thing with the TCI 6X is that it gives you 6 forward gears that you can shift completely manual with the gear lever (only 1-4) or with paddles behind the stearing wheel. They do sell a kit which contains a stand alone computer so it should be minimal changes to plumbing and wiring.

The car would also look completely stock on the outside and one could even keep the original gear shifter.

A complete kit seems to run arround the 5.5k$ mark which is pretty expensive but it would probably completely transform the driving experience. Don't you think?

//Robert

 

Hi,

Thank you for quick replys. I do think it is a reasonable bolt-up.

http://www.rowand.net/shop/tech/automaticoverdrivetransmissionswap.htm

They do have different diffrent physical packages but many things seem to be the same. Please check the above web page for more details. Lot's more !

The yokes seem to be interchangable to a degree so that does not seem to be a big problem. A potential problem may be that that the 4L80 may be shorter! But that is not likely.

I will talk to my gearbox specialist to see if they can undertake a swap.

Summit racing is selling the kit for 5.8k$
http://www.summitracing.com/parts/TCI-271600P/

Any thoughts?

//Robert

 

Thanks for all the input.

A couple of observations.

I agree that it probably take some work to get the torque tube right. The rest should not be impossible.

The reason for me to do the change on my car as opposed to buy a 5-speed is that mine has only covered 30k miles from new and I'm the second owner. The second reason is that it is a Straman convertible which kind of limits the alternatives.

On the gear issue I don't totally agree. The 6 speed has a 5th gear which is 1:1, i.e. the same as the original 400 box. This means that there is no horse power issue as the gearing on 5th will be exactly the same as in third gear with the TH400. The 6th gear is a overdrive with 1:0,75. Mine does above 3000rpms at 60mph so reducing that with 25% at plain highway cruising would be nice. Horsepower cannot be an issue either as the engine would stay above 2500 rpm’s with limited load.

This means that the 6 speed gives better options to keep the engine within power band up to 5th gear and a possibility to lower the rpms with 25% when cruising on the highway.

The rear axle differential gearing should not be an issue either because the 5th gear is the same as the 3rd gear on TH400, 1:1. The only difference is 5 gears instead of 3 up to 1:1 and an additional 6th overdrive to reduce rpms 25%.

I also think a programmable 6L80 gearbox should change gear quicker and also give the possibility to use lock-up for most gears.

Surely that must transform the driving experience.

Thoughts?

//Robert

 

Thank you for all the input.

A 456 would be nice but there were even fever convertibles done of them (again Straman built, like mine).

Part of the fun with my 400 is that it is a convertible and that also limits the need for speed resources. Another limiting factor is the weight, it’s way to heavy to be a mover.

And the 456 is not really a fast car either. I built and used to run a supercharged Cosworth powered TVR with 550 Nm rear wheel torque in 930 kg car so most of the stuff out of Maranello, short of the supercars, is fairly slow up to 200km/h....

And I’m pretty happy with an auto box with the usage of the car. We use it on nice days and only for road use. Having raced a few years back in the dark ages, putting the 400 (and most of the older cars) on the track is not really my thing. When it comes to road use you always get stuck in traffic or find yourselves in endless sequences of stop-and-go du to traffic lights and/or crossing roads. Hence an auto box that let’s you use gears within the power-band, which the 3-speed TH400 does not, combined with being able to shift manually should suit me just fine.

The trick is not really the paddle shifter but to be able to keep the engine within the power-band and to manually shift combined with running full auto on my way to Stop&Shop…

On the issue GM 6-speed from Corvettes and a like it is much more difficult. These boxes have half of the electronics in the box and half of the electronics in the electronics box in the car. So far no one seems to have been able to make a stand alone programmable controller for usage with non computerized engines. I think that part of the reason is that the box communicates trough a CAN-bus and requires a lot of sensor data that does not exist on a non computerized engine. I have swept the net several times to see if anybody has been able to mate these new boxes with old engines. Sure, many have been mounted in old cars but always with a modern engine. If anyone else has seen anything different I would appreciate an update.

Unless someone comes up with a viable alternative I’m probably going to order the TCI 6-speed after the summer to have all installed and ready to go next summer.

//Robert