I recently purchased a 1963 3/4 ton Chevy Pickup... nice body but in need of some mechanical help..
The tranny is the factory 4speed and it is slipping out of 3rd gear
when throttle is released.. it also has a very "old vehicle" mechanical
whining sound... like an army jeep on MASH..
The truck currently tops out at 60-70 mph ..... it has 4.57 rear

Since the trans needs an overhaul, and it doesnt allow crusing speed,
and is old school noisy... I was thinking of replacing it with a 4+3
from a C4.

I live in Dallas and there is a trans shop in Weatherford,Tx (60 mi)
that specializes in making custom drive ratio automatics..

The idea would be to leave the rear end ratio alone and use the 4+3
as the upgrade and speed problem solver for the C20 heavy cheby
with custom ratio allowing well tailored trans/rear end workable combo.

I have NEVER owned a 4+3 and don't know their quirks or strengths
My neighbor had one in a 87 Z51 that he bought quite cheaply because it had a trans issue..

1. What do I need to watch out for?

2. Are there any weak links in this trans??

3. What is the cheapest/best way to go about getting a complete
unit.... what should I expect to pay..ballpark??

4. Will the 4+3 stand up to trailering duties???

5. What are some good resources I can read to familarize myself
with the 4+3?

6. Are there known and tested upgrades for the 3spd/OD section
of the package?? who makes the upgrade?? website?? phone?

Any suggestions here would be apprecaited... thanks...Kyle

 

Anyone know the torque rating on the 4+3... or know who has that
info?

 

Lots of answers here.

www.5speeds.com/dne.htm

Repairs
www.skspeed.com/aboutsk/transshop/default.asp

May have to fab custom shifter as Vette one was mounted to tunnel and no aftermarket versions made

 

The 87 Callaway Corvette used the 4+3 and that motor put out 465 ft-lbs of torque and 345HP.

The 4+3 box does not use a tranny mount so that would be a problem. You would have to fabricate some way to add a mount tab to the tranny. The output shaft size and the splines are different than the truck tranny so the front half of the driveshaft assembly would have to be a custom piece. The OD unit also requires a small tranny cooler.

Then you have to deal with the electronics portion to get the tranny to work. The ECM controlled the OD portion and used coolant temp, throttle position and a mechanical switch to operate the OD (which is a 2-speed unit) In the 87 Vette, the OD can actually operate on all 4 gears in the tranny.

Because the 4-speed portion of the tranny is a Borg-Warner Super T-10, you can probably adapt a Hurst Competition Plus shifter but there are no mounting holes on the tranny for the shifter mechanism. The shifter will be a difficult part of this swap.

You might be better off using a 700R4 automatic with an OD. Much easier to install and less wiring and they can be built to be very strong. Even a Turb0 400 with something like a Gear Vendors OD will be a much better deal.

 

Wow... I remembered the problem of my compadre's z51 was electronic
but was fixed simply.. ( I believe a wire had come loose and was plugged back in)...
The OD is partially controlled by coolant temp??????... yuck..
I wonder if anyone has built a manual overide switch.... like maybe a
Bonneville guy who needed to stay in OD regardless of temp..

looks like some fab work also....

the gear vendors stuff is stout.... but pricey... not worth the job it does in my opinion... it would be a cool toy at a lower price.. but I really stopped considering them after I saw their price sheet

mechanical fabs are usually the easy part.... but I don't think I could get over the electronic hurdle... and I wasnt planning on running a L98
w/ecm up front

I am a little bummed about this.... I had thought about this type of
modification for a while...if the od/box was manipulatable it seems like this would be some uber-slick problem solving for this ap...

Might be easier to set up a 6spd with double OD gearing
regular 1-4... then 2 different OD ratios

I would still like to hear from those who possibly have a solution to using the 4+3

 

I did read an article in JP magazine on how to manipulate the Rubicon's
electronic axle locking mechanism... for full time axle lock... it was a remarkably simple "wire and toggle switch" solution....
any chance of that here????????? on the OD?... I could incorporate an 18 wheeler type shifter where the range select was changed to be the electronic toggle...

 

"Then you have to deal with the electronics portion to get the tranny to work. The ECM controlled the OD portion and used coolant temp, throttle position and a mechanical switch to operate the OD (which is a 2-speed unit) In the 87 Vette, the OD can actually operate on all 4 gears in the tranny."

This is true, in the original Vette app but to make the O/d unit
engage / disengage; only need switched 12V supply to solenoid.
Would not have kickdown feature but it would still operate
as intended