1975. I've been working on getting the halfshafts out. Everything has a good bit of rust. I already have the flange at the wheel loose and I have the nuts off of the u bolts at the differential, but the U bolts themselves almost seem welded in place. I've tried heat, plenty of penetrating oil and a hammer and punch trying to knock the u bolt off and it hasn't budged one micron.

Has anyone ever had to cut a u bolt strap off before?


Thanks,
.

 

Sounds like you do have a bit of rust going on. Assuming your in there to replace U joints. And your straps are that rusty. You should probably look at replacement anyway.
That said. The best penetrating oil I have found is a half and half mix of acetone and ATF. Automatic transmission fluid you may already have. I found a small bottle of acetone in the paint department of a big box hardware store. Mix it up 50-50 in a old spray bottle. I used this when replacing my body mounts as I didn't want to spin off one of the caged nuts under 2 and 3 mounts. Of all penetrating oils you can buy. This inexpensive homemade brew works the best.
Those straps are inexpensive. Maybe just pick up 4 new ones. And feel guilt free when you cut them!

 

Thanks for the reply. I'll definitely look into that home-brew, because the prices on these store bought penetrating oils is getting out of hand. I inherited this car, and it has sat for 15 years, undriven, on a concrete floor in a barn, so things are quite seized. As you stated, I need to replace all the u joints due to binding of the old ones, and I wondered if I should go ahead and replace the drive shaft u joints as well because the last person to install them put them in backwards and I can't access the zerk fittings.

 

I have had diff's come in with u-bolts seized in the axle yokes. Some were so bad they wouldn't tap out. I would try Kroil or make up the Mix that 4-vettes mentioned. Since you are working on an older, rusted car, grab those inner axles and see how much play is in them, chances are if they have never been replaced the diff is going to need attention.

 

I assume we're talking end play, or rather if I were to pull on the diff yoke in the direction toward the wheel. If so, what is the tolerance for how much movement is normal?

Thanks,

 

End play on those diff side yokes is really common on these mid 70's car's. I'm not certain of the outside wear spec. But Gary will have an answer.
Generally, when you push it in and pull it out. If there is more than 1/16th. of an inch they are worn.
if you have more than that, and highly likely you do. You'll be like me. Wondering where I can get a replacement yoke.
Basically your looking at a diff rebuild.

 

Tonight I cut off the passenger U Bolts. I got the halfshaft out, but the threaded end is completely stuck with no way to remove it. It looks like I'm going to have to pull the yoke on the diff. I'm afraid to ask..... What exactly am I going to have to do to get the diff. yoke off?

 

That's easy. To answer. Drop the diff out. Remove the leaf spring. Remove the strut rods and carrier. Remove the front snubber bolt. Support the diff with a trans jack or carefully with a floor jack. Unbolt the frame crossmember at the sombreros. Lower diff and crossmember while prying on the rubber sombrero mounts. Perhaps you need to do a google search on rear diff removal.

 

Or, you can cheat like I have. Drop the spring out of course. Leave the snubber in place. With diff held up tight with floor hack. Reach over the top of the crossmember and remove the bolts that secure the cover to the crossmember. Been awhile, but I did it. I have a huge selection of tools mind you. Once the bolts that mount the cover to the crossmember are out. With diff very secure with a floor jack. Remove the cover bolts. The clip that retains the yoke is right in front of you then. A pair of right angle circlip pliers comes in handy. Remove the clip and slide the yoke out.

 

I recommend if you are going to pull the diff out you take your time. Remove it with the crossmember, plenty of info on that here. It is 100lb of iron, don't take any chances.

 

About everything that can go wrong, according to others' accounts I've read, has gone wrong. Among the worse so far, I found that one of the tabs on the back of the rear end housing was already completely sheared off before I even began taking the bolt out. I'm hoping I have have it welded back on.

 

No. That's cast. Get a replacement heavy duty cover. Replaced mine years ago with a Muskegon one.

 

Yes that cover is junk now. Prices are going up on everything, covers included so I wouldn't wait. That breaks many times from improper installation and loading. Make sure you understand how to install one. It can also happen from impact like a pothole but usually it is installation loading. There were 2 covers too in case you look for a used one. 63-77 and 78-79 both will bolt up to the housing, but the spring pads and bolts are different for the spring change in 78.

 

Thanks guys. Since the bolts are broken off in my axle yokes I'm wondering if it might be easier to just purchase new ones. If I bought new ones, would they have to be ground down to make sure the they have the correct clearance from the center shaft in the diff, or are they pre-cut to the right size?

Thanks,

 

If you find some of high quality. Please let us all know. I keep asking on here where I can find a good one.

 

I too had this brake on me,,, the night before we were leaveing for Power Tour. ( we went any way, but took a different car ).

,,,,,,,,,,,,,,before,,,,,,,,,,,,,

😁 After doing everything 👍 ( over one winter season )
.
There are a few tips we can share as you go along. Just ask here before you dive in.

( some of us enjoy working on our old junk )

 

That looks really nice. I suppose I'll take it one step at a time. I've got the spring pack out and I've been soaking the sombreros with penetrating oil for several days. The next step is getting the diff out and I guess I'll measure the end play to get a definite number on the side yokes. Since no one seems to have much confidence in the aftermarket yokes, I may just keep what I have as I don't want to wait until next year to drive the car, and I also don't drive it very often.

 

Serviceable iron differential cores are always a strong buy. Perhaps you rebuild one, perhaps you use one, but it's worth checking Facebook, Craigslist, and your local hot rod shop to see if someone is selling one.

 

Good idea but some thoughts to consider.
1- prices are way high on cores now. Most are NOT worth some of the prices I see advertised. There really isn't a shortage of these either,
2- many selling them have no clue what they're selling, other than it's a corvette used diff and is worth as much as Oil Oil today. Actually, Olive oil is a better deal!
3- Know the differences of the run, the 63-79 are all iron, with the exception of the 63 GS. They will all bolt in any 63-79, the only immediate check would be the pinion yoke size. However, they are not all created the same. There was not one year of the 63-82 run that didn't have diff issues. Yes, many were sold and driven without an issue- I am not saying otherwise but there were issues from the start and there were several revisions.
4- Rebuilders pay about $250 for cores give or take. Since a core is usually unknown it can be a gamble and why many want a $500 deposit to cover bad cores.
5- Look inside and learn what to look for. I have seen diffs for sale at swap meets with blown apart posi's in them. One case comes to mind. Nothing special, a C3 diff, it wasn't worth $100 yet the guy wanted $400