I'm starting to think about replacing the 4+3 in my 87 to be able to see higher track speeds without risking destroying the OD unit. Everything I have read here is that the OD simply doesn't like being abused with high RPM engagement. The car sees a number of track days and without using the OD, speeds are limited.

I have been following the thread in the "Transactions" sub-forum regarding Keisler. It seems that Keisler has had some issues providing their trans and not only that, they have apparently filed for Chapter 7 bankruptcy as of the 17th.

Is there another company that builds a TKO Tremec bolt-in trans for C4's?

 

Why not just get a zf out if a later model?

 

My 86 was originally a 4+3 but had a tranny swap to a Tremec 5 speed before I bought it. Working out well so far.

 

I too would like to know of something. I have 3.75s in my 85 and a 4+3, with my modifications, I'm pretty confident I wont make it to the finish line without going into overdrive at the 1/4 mile. So the delay for the engagement will definitely hurt my time.

I called a Corvette junk yard and they said $1200 for a ZF6, and that wasn't with all the conversion parts and stuff. I wouldn't mind going to a 5 speed, as long as I can make it down the 1/4 mile.

 

Keisler is the company that filed for bankruptcy so they are out of the picture. It was Keisler that offered a bolt-in conversion for the early C4's with the 4+3. That company also offered a 5-speed and a 6-speed. The Tremec TKO transmissions that were offered for the conversion are still available, but they are not the specifically modified ones.

The RPM you will see in the traps can be changed by tire diameter. Taller tires will drop RPM somewhat. There are calculators for determining engine RPM at various speeds so you need to do initial calculations and use your tire diameter to start. And definitely make some passes to see just where the revs are at the lights.

As an example, at 5000 RPM with 3.75 gears, a 1:1 4th gear, and a 25" tire diameter is just over 99 MPH. Simply changing to a 27" tire results in a 107 MPH speed. You can play with values here

Don't even think of engaging the OD for drag racing; not only is there the time delay, the OD just doesn't have the strength for WOT shifting.

A ZF would be the logical choice for replacing the 4+3 but I think the big concern is how good of a unit one could find. From what I have read, rebuilding a ZF can be expensive and you still have to deal with the all parts needed for a conversion and cutting the trans tunnel to get the shifter thru the console.

 

Where did you see Tremec filed Bankruptcy? Just did a search and found Keisler apparently did but nothing on Tremec.
If they did, I'd be interested especially in where I get parts in the future if needed.

 

Ooops!! My bad It was Keisler that went belly-up. Tremec supplied the transmissions for them.