T-56 upgrade question

[Black85]

Hi,
this is the first of many posts on an 85 that I'm going to be restoring over this winter.

Is the T-56 trans a direct retrofit for the 4+3 trans? Will it work ok with the stock ECM?

 

[ErnieN85]

Is it a bolt in probably not.
best bet for a bolt in ZF6

 

[Black85]

forgive my ignorance, but...

Ernie,

Could you please elaborate on the ZF6? What year are they "stock" in? Also, when you say that the T-56 isn't a direct bolt-in, do you know what complications will be encountered? Sorry for the ignorance here, I'm used to building Cobras (Ford powered), so this is my first experience in the bowtie/vette realm!

The 85 that I'm rebuilding this winter has some major issues due to the fact that the owner installed a Procharger with too much psi, so the engine needs rebuilding/replacing, and he also mentioned that the trans doesn't work very well, that's why I'm considering some sort of "straight 6-speed" trans swap instead of trying to sort the issues with the stock 4 + 3. It was my understanding that these don't hold up well in high hp applications.

thanks, Brian

 

[c4cruiser]

The C4's have a torque beam that attaches to the tranny tailshaft housing. The T56 does not have these holes so some sort of fabricating would have to be done. There are probably some more problems that would crop up id trying this swap as well.

The 4+3 is a fairly stout unit The main box is really a Borg-Warner Super T-10 and the OD was built by Doug Nash. The Callaway twin-turbo cars used them with no mods when those cars were built and the motor put out around 375HP and tons of torque. The key to long life in the 4+3 is maintenance. Changing the fluid in the OD portion at regular intervals is important for long life. I use Mobil-1 synthetic ATF in my 87 and change it once a year. This is my autocross/track day car and it doesn't really see a lot of street miles so the fluid never has a chance to get dirty or comtaminated. It's not too tough of a job so I do it at home.

One alternative to consider is the Richmond Gear 5-speed or 6-speed. They have a version specifically for replacing the 4+3 and it already has the holes for mounting the C-beam. You only need to enlarge the floor tunnel hole for the shifter.

 

[Black85]

Thank you for that additional info! I haven't had a chance to get it to the shop to take it apart yet, so I wasn't even thinking about the torque tube problem! I'm trying to get all my research out of the way while I'm waiting.

Does anyone make a performance shifter replacement for the 4 + 3? He mentioned shifting problems, so if I rebuild the existing trans, I'll probably want to swap out the stock shifter anyway.

Brian

 

[ErnieN85]

Brian, the 4+3 is a Muncie so you should be able to use a Hurst shifter. the only catch is the overdrive shift button