PaulUptime

Hi folks.

The dif my '65 is has been making some whiny noises over the past few years. By the time we arrived in Carlisle last year (8 hour drive) it sounded like I had a supercharger belted down in the back!

I have been addressing other items further up the drivetrain and this spring will need to do the diff. Funds and time available for this job have been tight so I've needed to hold back on the diff job, but I'm going to need to do it.

I have read much but know very little about how sophisticated a repair/rebuild this would be. Admit I'm a bit intimidated after reading JackFit's incredibly detailed Gary Ramadei rebuild story, so would appreciate any good thoughts or advice. With apologies for stating the obvious, I want this done right and done once.

1. How long a job (avg) is it for an experienced tech to rebuild a midyear differential?

2. What should be my expected cost?

3. Should I seek out a tech specifically experienced with midyear diffs vs someone with general diff experience? Are our diffs that unique?

4. I am not concerned with originality (that ship sailed long ago.) Is it possible to buy an already rebuilt midyear posi diff, or are there perhaps any newer, better diff designs available?

Much thanks, in advance!

65specialk

You will be glad you did. Are you sure it is not a wheel bearing?

4 Speed Dave

Doing a 63-67 rear is no different than a 10/12 bolt or any other rear end. However the one thing that is different that most shops might not know is that you can't use the typical super shim side carrier bearing shims. These early mid-year cases are narrower than the later cases and you need to use the original style fixed thickness carrier shims. Not many people have these shims anymore. The later corvette cases are wider in this area of the case thus allowing the super shims that come in most bearing set-ups kits to be used. Years ago when ebay was mostly used by regular people I bought out a guy who had a boat load of GM shims still in GM wrappers and everything so for myself setting up these rears is not an issue. Other than that, backlash, pinion bearing preload gear pattern is all the same. Another item to note is that most standard bearing kits have the new stub axle needle bearings that have only 1/2 the amount of needles in them as the original bearings. Timken has the correct bearing with the full amount of needle bearings.

PaulUptime

Thanks for the suggestion. The answer is no, I'm not sure.
My rear trailing arms have never been off, so it could be.
Probably should do those at the same time.

The sound from the rear is only under load (no sound while coasting) so would that itself not rule out it being a bearing?

The holdup for me for just doing the T/A's now is that I'm in Canada and while Toronto's a big city with resources, Corvette parts are not one of them. The cost to ship/bring back new t/a's to swap becomes a bigger deal for me. I regularly visit the Detroit area, so if doing them would probably order a set already done shipped there, then bring them back into Canada myself. I figure the T/As will cost me about the same as the diff job (about $2k CAD)

PaulUptime

Thanks Dave.

Obviously I'd like to have all the parts, etc. in order before dropping the diff. I want to avoid having the car in a shop for an extended period. Ideally would want to drop the dif out at home so the car will be safer here than in a shop, but do not have a lift for putting it all back together.

This is why I was wondering about just getting a full replacement diff new, or rebuilt. Not sure if that's a better option.

MikeM

I'd find a good used one if money is tight.

If you keep grease in them, they can last a lifetime and longer.

MarkC

Jackfit had his rear end rebuilt several years ago and he posted on here about the experience. I think he is in now in Italy but you may want to do a search.

GUSTO14

Paul, check out this link. You'll need to go down about halfway to get to the Differential. It is extremely detailed, but I think you'll find it interesting and illuminating. I believe it was done by the folks at Vansteel for CHEVY DIY...

http://www.chevydiy.com/c3-corvette-...al-reassembly/

Good luck... GUSTO

dkleather

Here's a great place for rear parts, rebuild, or replacement if you choose that route. They are great to deal with.
http://www.bairs.com/

65tripleblack

You can save money by doing the posi case yourself, but you should have an experienced mech set the ring and pinion, which is where your noise is probably coming from.

There are a lot of good mechanics that can do a good job setting up the ring and pinion: Bairs, VanSteel, Tom's, Gary Ramedei to name a few. You shouldn't need to upgrade unless you abuse or race your car. If you upgrade, then you're involved in hybrid u-joints.

GTOguy

This is solid advice. A quiet, never-been-messed-with third member will probably outlast you. On the other hand, to have a qualified technician disassemble, inspect, replace needed parts, and overhaul your third member will require a lot of money and time, if hard to get parts are needed. Almost 30 years ago I had a GM solid axle rear end re-done by an expert, and it needed average work. The bill then was $950. Today, that bill would be closer to 3k. If you are getting whine on acceleration only, it's more than likely ring and pinion wear, and not a wheel bearing.

mrg

A good way to go. .. I bought a used 3:08 diff to replace the 4:11 in my car from a wrecking yard in LA. The diff unit came out of a '71 car. I wanted 3:08's for the way the car is used now (road trips).
Price of the diff at the time (2003) was $400.

The swap was fairly to do the old school way (floor jack and jack stands). A combination U joint was used to mate early driveshaft trunnions to larger later style pinion trunnion size. Caps instead of U bolt straps were needed to mate side yolks to half shafts.

The diff swap has worked out well. No issues in almost 20K miles driven.
​​​​​​​John

Frankie the Fink

If you can source a used, good third member do so...
If not then I've dealt with Tom's Differentials before.
Straight up, no BS....

pop23235

Get a used unit. They are all around. Get one close as shipping is not cheap. I've got a 65 3.70 posi in the garage. Shipping to Toronto would kill any deal, so look closer to you.

C2 Hot Cam Guy

You can get a rebuilt one w a 1 year gaurantee. Hard to tell condition on a used one . I just got one & you can pick gear ratio in case you want faster 4;11 4;56 or better gas mileage 3;08 3;23 $ 1095

ejboyd5

Might it be worth a few dollars to change the lubricant before going any deeper into the differential?

65tripleblack

Just think.....if you buy a junked one and that one has problems, then you can negotiate from a strong position because then you'll have 2 diffs that need rebuild and maybe you can get 2 for the price of 1 overhauled.

Not only that, but look at all the great exercise you'd have gotten installing and removing the junked diff. No need for Weight Watchers.

OP: Does it whine on the coast? Pull?

hope2

pinion bearing suspect if noise only on load. ck. might be cheap fix.

pop23235

Once it starts whining, the fix is replace. Either the gears at min. or the assembly. It's next to impossible to set up worn gears.

Easy Rhino

Here's my problem. It may or may not be the diffy. In general, differentials last longer than wheel bearings, so there's that, if they are all original, and reasonably low miles. If it's a wheel bearing, you could spend some good money on the diffy and fix nothing.

Going for all three may prevent worrying about it for the rest of your life, but would cost a bunch.

You stated that the trailing arms have never been off. If thats true, I would be suspect of the wheel bearings. Add this to it: if the sound grew perceptibly worse on a long trip (not just "it sounded louder because it was beginning to bug/worry me"), keep in mind that the diffy is lubricated at all times, but the wheel bearings are in grease that is how old (?) and gets heated up when the bearings are dodgy, which increases the noise.

Just saying before you do a deep dive, you may want to try to do some confirmatory checks.