69 rear end rebuild

[Don W.]

I have a 69 427/390 THM400 auto; the previous owner changed the rear to ~4.11 using the matching numbers case. A few qustions:

1. Any recommendations on firms that I can ship the rear to for a complete refresh and conversion back to the original 3.08s? Any member experience on this?

2. What are the general steps to remove and replace the rear end and what is the level of difficulty?

Thanks for your input,

Don

[Chuck G.]

Re: 69 rear end rebuild

I have a 69 400HP THM 400.

The original 3.08's were howling. I replaced them with a set of 3.36 gears.

I took my rear to my local Corvette shop. He's been doing rears for 35 years, and I've known him for about 30 of those years.

I'd try a local guy. There are many rebuilders who advertise in the Driveline, etc. Shipping can be a problem, as is the cost of shipping.

Taking the rear out is pretty straight forward for an average mechanic.

Don't try to take just the rear out. Drop the entire differential crossmember with the diff attached. You'll need a BIG prybar to pop the ends off the sombrero bushings, but that's the easiest way.

Of course, you have to remove the spring, the camber rods, the diff snubber, and loosen the driveshaft. You also have to remove the half shafts.

Chuck

[Joe C.]

Re: 69 rear end rebuild

I have a 69 427/390 THM400 auto; the previous owner changed the rear to ~4.11 using the matching numbers case. A few qustions:

1. Any recommendations on firms that I can ship the rear to for a complete refresh and conversion back to the original 3.08s? Any member experience on this?

2. What are the general steps to remove and replace the rear end and what is the level of difficulty?

Thanks for your input,

Don

Don,

The most difficult part about R&R of the diff, is compression of the leaf, to allow removal of the links. Also, care is required in reassembling the spring to the diff cover, as improper bolt tightening procedure can lead to broken diff cover. As far as rebuild of the differential itself:

Level of difficulty: 9 on scale of 1 - 10. Not for the shadetree mechanic. Special tools required.

I find this difficult to say, because I like to do everything myself. With the exception of the limited slip unit, which is a do-it-yourselfer, this is the only job that I leave to the experts. One major reason is that removal of the carrier from the case normally requires a spreader tool. Correct alignment of ring and pinion along the ring gear's thrust axis is critical, and requires trial and error with varying shim packs. Proper pinion gear setup requires equal precision.

[William V.]

Re: 69 rear end rebuild

To change from 4.11 to 3.08, 3.36, 3.55 or 3.70 will require changing the ring gear housing. I suggest you have a compenent local shop set up the rear.

[Chuck G.]

Re: 69 rear end rebuild

I'm the "general contractor" on jobs like this.

I'll pull the rear, but I wouldn't even ATTEMPT to rebuild it myself.

I take it to a pro, get it back, and re-install it.

Same thing with transmissions and motors.

Chuck

[Jim T.]

Re: 69 rear end rebuild

check out www.bairs.com. They will send you a shipping box. Also check out www.contemporycorvettes.com, they may have a used 3:08 unit to fit your numbered needs. Your 69 is sure going to drive different going from a 4:11 to a 3:08. Whats your pedal to the floor shifting speed with the turbo and the 4:11 gears? I have a 350/300 70 turbo that would shift from first to second about 60 MPH and about 90 out of second.

[Don W.]

Re: 69 rear end rebuild

I go from 1st to 2nd at about 15 mph

[Michael A.]

Re: 69 rear end rebuild

Don,
You might want to try Darrell Shepherd in Vemillion IL. He has a good reputation and rebuilt my diff about 10 years ago. I've put about 25k miles on it since and it is working well.

His web site is:

http://www.pipersauto.com/4speeds.html

Cheers