damaged differential advice

[Tim D.]

I am looking for advice on my damaged differential. I just finished a complete restoration on my 64 conv. I literally replaced or rebuilt EVERY nut and bolt on the car EXCEPT the differential. Well, as they say, you are only as good as your weakest link. I have put about 650 miles on the car and as I let the clutch out to pull away at a stoplight, I heard/felt a loud clank/clunk....the car lurched forward about a foot with a screech and stopped. I immediately shut it down. After checking underneath and not seeing anything unusual, I started it back up and tried to move it, but no dice. I shut it off and discovered it would not roll forward at all, but it would roll backwards (by hand pushing the car in rush hour no less). I had it towed and I removed the drive shaft and realized the pinion flange was dangling loose similar to a broken wrist. I am not yet sure if the pinion flange is the only problem or did I break the ring and pinion or ?

My question is...what to do? Would you advise pulling the rear end/pumpkin and completely disassembling it and then fix only what appears to be the problem OR disassembling it and having it COMPLETELY rebuilt by a professional?

My common sense tells me to have it completely rebuilt by a pro (as long as I'm in there). If this is the best option, then who do you all recommend I send it out to that will do it properly the first time (ring and pinion, gear set up so there is no "noise", clutch pack for posi-traction etc, side yokes). I live near St. Louis, MO. The rear end is the original for my car with all correct numbers etc. It is a 3:36 four speed.

All thoughts are greatly appreciated!

Thanks in advance.

Tim

[Tracy C.]

Re: damaged differential advice

If this ever happens to me, I'll send my parts to Gary Ramadei. You can reach him through the "Membership List" link in the narrow blue bar at the top of this page.

I've only heard positive things about his work and he frequently posts helpful info on this discussion board.

good luck,
tc

[Duke W.]

Re: damaged differential advice

I had it towed and I removed the drive shaft and realized the pinion flange was dangling loose similar to a broken wrist. I am not yet sure if the pinion flange is the only problem or did I break the ring and pinion or ?

Tim

It sounds to me like the drive pinion snapped in two... happened to my SWC at about 30K miles when I lifted off in first gear then flooring it - BANG!

You're going to have to pull the axle and have it rebuilt. It will probably need a new (or good used) ring and pinion, so you might as well get a new Positraction case assembly and replace all the bearings and side yokes if necessary.

If the job is done right, it should last forever.

Duke

[Joe L.]

Re: damaged differential advice

I am looking for advice on my damaged differential. I just finished a complete restoration on my 64 conv. I literally replaced or rebuilt EVERY nut and bolt on the car EXCEPT the differential. Well, as they say, you are only as good as your weakest link. I have put about 650 miles on the car and as I let the clutch out to pull away at a stoplight, I heard/felt a loud clank/clunk....the car lurched forward about a foot with a screech and stopped. I immediately shut it down. After checking underneath and not seeing anything unusual, I started it back up and tried to move it, but no dice. I shut it off and discovered it would not roll forward at all, but it would roll backwards (by hand pushing the car in rush hour no less). I had it towed and I removed the drive shaft and realized the pinion flange was dangling loose similar to a broken wrist. I am not yet sure if the pinion flange is the only problem or did I break the ring and pinion or ?

My question is...what to do? Would you advise pulling the rear end/pumpkin and completely disassembling it and then fix only what appears to be the problem OR disassembling it and having it COMPLETELY rebuilt by a professional?

My common sense tells me to have it completely rebuilt by a pro (as long as I'm in there). If this is the best option, then who do you all recommend I send it out to that will do it properly the first time (ring and pinion, gear set up so there is no "noise", clutch pack for posi-traction etc, side yokes). I live near St. Louis, MO. The rear end is the original for my car with all correct numbers etc. It is a 3:36 four speed.

All thoughts are greatly appreciated!

Thanks in advance.

Tim

Tim------


You have no choice at this point but to remove the differential carrier from the car and have it repaired/rebuilt. There is absolutely no viable option.

The thing I do not understand is this: a catastrophic failure of a differential unit like this is somewhat uncommon. As I understand it, this unit is original to the car, worked just fine since new and was untouched as part of your overall restoration. Then, 650 miles afterward, it fails catastrophically. That just doesn't seem likely to me. Did you, perhaps, remove the fluid and forget to replace it which could have resulted in the catastrophic failure?

Also, I completely concur on Tracy's recommendation of Gary Ramadei.

[Domenic T.]

Re: damaged differential advice

Tim,

with that kind of failure I would be concerned with saving the original case.

I have done these before and they are not easy unless you do them all the time.

I like what Gary has to say, sounds like he has a lot of experiance.

DOM

[Ray K.]

Re: damaged differential advice

Tim

It seems very likely that the pinion gear shaft has snapped, thus leaving the pinion flange dangling from the driveshaft. This failure requires that the complete differential be removed and disassembled and inspected. At a very minimum, you will need to replace a ring and pinion gear set and an inspection may reveal some other part that suffered due to the shock load.
New bearings, seals, and positraction components ( if it is a positraction ) should also be replaced.

Ray

[Gary R.]

Re: damaged differential advice

Hi guys,
I just saw this thread and can offer you some advice on this issue. Thanks to the those that also mentioned my name.

DISCLAIMER:Now one thing I want to say to those naysayers here, this info is not posted here to promote my own purposes but rather to offer help to Tim and his problem. I hope I can answer all his questions so he can decide which direction he wants to go in. It's almost impossible to tell someone how to rebuild or better build these diff's without pictures, they tell the real story. I also can't instruct someone on something if I haven't done the job myself, so take this info for it's intended purpose and nothing more.

Assuming you still have an original '64 diff then you have some issues there for sure. First off from your description the diff has to come out, sorry but it's the only way. Not as bad as removing an engine though and can easily be done on jack stands and a jack to support it. Remove the diff with the cross member attached much easier to do then some of those old manual procedures which the cover is split in the car to remove.

With the diff out look at the casting date on the LH side, this is a Letter and 2-3 numerial code= A134 would be Jan 13 1964 or 1974. The fast way to know if you have a '63- '64 is the front mounting hole for the diff bracket is tapped 7/16-14. The 65-79 housings( carrier is the correct name) are thru holes for both. The rear cover on a 63-64 will have a large machine thread fill plug unlike the later 3/4 npt fill plus used. Since the covers were often broken that will not guarantee what the diff is only the cover.

Get the diff on a bench or mount it on an engine stand and the remove the rear cover. Drain out the oil and take a look. Chances are you broke the pinon and posi case. The 63-64 posi's were Dana units and not very strong at all. I used to call them junk but that would offend some so I'll just call them weak. Don't be surprised to find an Eaton and weaker Auburn posi in there. I'll post some pictures and links that will help you as well. I have open plenty of 63-68 diff and found them stone stock untouched. Others only God knows who worked on them and if they had legal eyesight that's how bad some are.

The 63-64 and some 65 used a coarse spline pinion gear and small " wedding band" crush sleeve. The 1310 pinion yoke was also the same spline and these parts are obsolete now. You can rebuild them but you need a new pinion yoke to match the new gears. The Dana posi's are also not recommended to reuse if not broken. You may find some old NOS posi parts but good luck and it will still be a weak link. Look at the pictures to see if yours looks like the 64 I pictured. The springs are long and on the outside. The Eaton posi used from 65-68 are also weak due to the casting seam locations, these can be ID'd by the small " postage" stamp window in them. If you find one of these check it very very closely for cracks. Any cracks found and the unit is junk as well, oh sorry, it's all done! LOL. If you see a large "tear drop" window then it is the 2nd design Eaton and those were used from 69-79 and are pretty good. I can mod them to hold up to 500-550hp with the correct machine work and parts. These will crack too but no where as much as the 1st design. I'd say 60-80% of the 65-68 diff's I open have cracked first design posi cases. Those who may have stopped at my booth last month at Carlisle may have seen the nice blended,polished and tuned posi I had on display, it too was junk I found a small crack in it at the large window radius but it sure looked pretty.

Here is a 64 I got in, looks like all the 63-79s like this.




Here is the cover and large plug, metal posi tag.


Here is the metal vent, the 65 up used a plastic vent, both work fine.



Cover off, Dana posi see the springs




Here is a 64 that has a 4 series Eaton posi, see the difference in the spring and casting? The 4 series was used with the 411 456 488 gear sets,the flange is thicker then the more common 3 series posi cases. For years a hot rod trick was to use a RG spacer with a 3 series case ,under the 411 RG. This is not recommended as many times the RG bolts loosened up and then the diff locked up and ended up in a lot of small parts!



Here is the old style pinion yoke.




If you want to see all my pictures and procedures take a look at these threads. They should answer all your questions and help you make a wise decision for you and your car. If I can help just let me know what your questions are. If numbers are not important I recommend finding a 71-79 diff out of an automatic and build that. They have better housings,posi cases,spiders,and have the thru holes in front. They will come with 1330 pinion yokes so you'll still need to get a new 1310 yoke or conversion joint.

http://www.digitalcorvettes.com/forums/showthread.php?t=77377

http://www.digitalcorvettes.com/forums/showthread.php?t=124412

http://www.digitalcorvettes.com/forums/showthread.php?t=110048

[Tim D.]

Re: damaged differential advice

Many thanks to all who replied to this thread. Sorry I have not responded until now but I have been researching and then had to go out of town for several days.

I have decided to pull my rear end and send it to Gary Ramadei upon everyone's advice. I have had several contacts with Gary and he really seems like a first class kind of guy.

I am preparing to pull the pumpkin out of my 64 Vette. I have an AIM and 63-64 shop manual etc and plan on following there sequence. I installed it all originally while the body was off of the frame. EVERYTHING on this car is new Except the rear end. I am planning on pulling the pumpking while still attached to the main cross member.

My question is are there any short cuts, tricks, cautions etc. that I should be aware of to make this safe, smooth etc. I will be doing it in my garage with car on sturdy jack stands and using my floor jack to compress rear spring and lower the pumpkin down and out of car. I know about using a chain for safety when releasing rear spring tension etc. Any thoughts about sequence, etc would be helpful. I haven't started yet, but it seems like I should/must drop spare tire carrier tub to make more room. Will I have to remove the undercar exhaust that I worked to hare to align/dial in etc.? When I remove half shafts and strut rods do I just remove them from the middle of the car or do I need to take them all of the way off from the outside/wheels/shock mount too? If I mark the camber adjustment, will I still need to get my car realigned after I put it all back together?

Thanks in advance, Tim

[Joe L.]

Re: damaged differential advice

Many thanks to all who replied to this thread. Sorry I have not responded until now but I have been researching and then had to go out of town for several days.

I have decided to pull my rear end and send it to Gary Ramadei upon everyone's advice. I have had several contacts with Gary and he really seems like a first class kind of guy.

I am preparing to pull the pumpkin out of my 64 Vette. I have an AIM and 63-64 shop manual etc and plan on following there sequence. I installed it all originally while the body was off of the frame. EVERYTHING on this car is new Except the rear end. I am planning on pulling the pumpking while still attached to the main cross member.

My question is are there any short cuts, tricks, cautions etc. that I should be aware of to make this safe, smooth etc. I will be doing it in my garage with car on sturdy jack stands and using my floor jack to compress rear spring and lower the pumpkin down and out of car. I know about using a chain for safety when releasing rear spring tension etc. Any thoughts about sequence, etc would be helpful. I haven't started yet, but it seems like I should/must drop spare tire carrier tub to make more room. Will I have to remove the undercar exhaust that I worked to hare to align/dial in etc.? When I remove half shafts and strut rods do I just remove them from the middle of the car or do I need to take them all of the way off from the outside/wheels/shock mount too? If I mark the camber adjustment, will I still need to get my car realigned after I put it all back together?

Thanks in advance, Tim

Tim------


You must remove the spare tire carrier and exhaust system (from the trans crossmember rearward). You must also remove the strut rods and strut rod center bracket as well as the spring. The half shafts have to be removed from the car, too.

None of the above is really all that difficult to do.

Most likely, the biggest problem you're going to face is the separation of the sombrero brackets from the sombrero cushions. This must be accomplished in order to lower the crossmember the carrier is attached to. To do this I recommend loosening the existing bolts in the crossmember cushions. If the crossmember separates from the cushions at this point, you'll be an extremely lucky person. If not, I recommend removing the bolts and installing bolts that are about an inch or two longer but just threading them in about 1/2". Then, using a LONG, STOUT pry bar wedged between the removable and fixed crossmembers, pry the removable crossmember down until the cushions separate. The bolts will prevent the crossmember and carrier assembly from falling on the floor.

[Tim D.]

Re: damaged differential advice

Joe, thanks for your input. I really appreciate it. That is pretty much how I expected it to go. I am hoping the cross member will come loose at the sombrero fairly easily, because it is all new. I had a VERY DIFFICULT time getting it loose on the initial restoration when the body was off of the frame. When I assembled it with new rubber cusions etc., I applied anti-seize goop to the bolt on each side that goes up through the sombrero cushions and attaches to the frame. I did know about the trick to loosen and/or use longer bolts so the cross member and diff don't fall on my head, but thank you for the reminder/heads up! I am reading my shop manual as we speak and planning on starting the project tomorrow morning when I'm fresh. I will report back with my progress.

Have a great day! Tim

[Gary R.]

Re: damaged differential advice

Hi Tim,
Joe covered it pretty good, the bolt threads are 7/16-14 btw. I don't like using the floor jack method on the rear spring. They can slip and you could end up with the car off the jack stands. I just use a 5' pinch bar under the spring end and over the strut rod. Then I slip on a 12' piece of 1.5 black pipe I have here, have a helper leverage it up to release tension on the spring while I remove the link nut and then lower it down. I have done it by myself using a jack but having a helper is much safer and faster. There is no effort doing it this way. Loading the ends I do the same thing.

I would remove the tire comp
Exhaust
mark the camber to get it in the exact spot if the alignment is good
unload the spring
disconnect the DS
have your jack or a tranny sissor jack in place
disconnect the front snubber bushing
extent the camber bolts and remove the 1/2 shafts
Then loosen the bolts and install the longer ones for added safety and see if the cross member pops off. The jack should be close to the diff to allow it to support it.
Lower it down and out.
Leave the T/S in place
Remove the cross member and bracket. Drain out the oil.
Check the snubber,replace it if it's an old one. same with the mounting bolts on the cross member.

[Joe L.]

Re: damaged differential advice

Joe, thanks for your input. I really appreciate it. That is pretty much how I expected it to go. I am hoping the cross member will come loose at the sombrero fairly easily, because it is all new. I had a VERY DIFFICULT time getting it loose on the initial restoration when the body was off of the frame. When I assembled it with new rubber cusions etc., I applied anti-seize goop to the bolt on each side that goes up through the sombrero cushions and attaches to the frame. I did know about the trick to loosen and/or use longer bolts so the cross member and diff don't fall on my head, but thank you for the reminder/heads up! I am reading my shop manual as we speak and planning on starting the project tomorrow morning when I'm fresh. I will report back with my progress.

Have a great day! Tim

Tim------


I did not realize that you had this out previously. So, you should have no trouble removing it now. The sombrero brackets should separate easily from the cushions.

[Tim D.]

Re: damaged differential advice

Thanks Joe. I was hoping it would pop loose easily this time around. I will install the longer bolts to keep it from falling before I'm ready for it. Tim

[Tim D.]

Re: damaged differential advice

Gary, thanks for the sequence. Dumb question.....you said, leave the T/S in place. What is the T/S.....trailing arm and shocks? Also, can I just remove the strut rods from the center bracket and leave them attached to the shock mount shaft on the outside and just swing the strut rods up and out of the way? Tim

[Gary R.]

Re: damaged differential advice

Gary, thanks for the sequence. Dumb question.....you said, leave the T/S in place. What is the T/S.....trailing arm and shocks? Also, can I just remove the strut rods from the center bracket and leave them attached to the shock mount shaft on the outside and just swing the strut rods up and out of the way? Tim

Sorry Tim- typo should have been T/A=trailing arm.