C3 rear diff crossmember

[Michael L.]

I am doing a frame off resto on my 69 and have everything off the frame but ran into difficulty getting the rear crossmember off. I have read the posts in the archives and I understand now this is not unusual and with the advice in there I believe I can get it down but my question is do I have to? Is this item something that should be replaced for this kind of a restoration? Does this bushing actually wear out?

Mike

[Harmon C.]

Re: C3 rear diff crossmember

I am doing a frame off resto on my 69 and have everything off the frame but ran into difficulty getting the rear crossmember off. I have read the posts in the archives and I understand now this is not unusual and with the advice in there I believe I can get it down but my question is do I have to? Is this item something that should be replaced for this kind of a restoration? Does this bushing actually wear out?

Mike

I see no problem with leaving it on. Most of the damage is done removing it.

[Michael L.]

Re: C3 rear diff crossmember

I still need to blast and paint the frame. If I decide to leave it do I need to take special precautions?

Mike

[Joe L.]

Re: C3 rear diff crossmember

I am doing a frame off resto on my 69 and have everything off the frame but ran into difficulty getting the rear crossmember off. I have read the posts in the archives and I understand now this is not unusual and with the advice in there I believe I can get it down but my question is do I have to? Is this item something that should be replaced for this kind of a restoration? Does this bushing actually wear out?

Mike

Mike-----


If the frame suffers from significant corrosion, I'd recommend removing the crossmember to inspect for possible damage to the cushion retaining tabs or cushion shells. The cushions are usually very long-lived. However, if there is corrosion damage to the cushion shells, that can create a later problem with the cushions "pulling out".

Otherwise, if you don't expect any corrosion damage, there is only one reason to remove the crossmember. That reason is to make it easier to get out the next time you want to remove the differential and you don't have the body off the frame. When I have the crossmember out, I usually coat the inside surface of the cushions with a VERY light coat of silicone grease for this purpose.

However, as Lyle points out, you can damage the cushions when removing the crossmember. This may well require replacement of the cushions.

[Mike G.]

Re: C3 rear diff crossmember

mine was stuck on there pretty good. i pryed it off after removing the bolts . i replaced the bushings with new ones. they hammered right out.

[Chuck R.]

Re: C3 rear diff crossmember

Hi Mike,

If your going to have the frame cleaned with some sort of media, I would definately remove the crossmember.

You don't want loose media material setting in the mounts, this may cause issues down the road.

If your going through the efforts to have the frame cleaned up, why not take a few more minutes and pull the crossmember off and inspect the mounts to play it safe. There's no better time than now.

Chuck

[Michael L.]

Re: C3 rear diff crossmember

Chuck,

Thanks for advice. The frame will get blasted so I will take out the crossmember and replace the bushings. It doesn't seem to me that I should cut a corner on something like that.

Mike

[Chuck R.]

Re: C3 rear diff crossmember

LIke Joe stated Mike, the odds of the mounts needing replacement probably are fairly low. I pulled my VERY corroded rust belt crossmember from my 68 and the mounts looked surprisingly good.

Unless they are severely checked up or splitting, they should still be ok to re-use.

Chuck

[Michael L.]

Re: C3 rear diff crossmember

I will check the mounts when I get the crossmember off. Will the WD-40 I have been soaking them with result in any damage to them?

Mike

[Chuck R.]

Re: C3 rear diff crossmember

If you leave the WD on them for an extended period of time, they may actually swell up and become deformed to the point of requiring replacement if you've drenched them.

In some cases, the rubber will shrink back into place once the excess is wiped off and they have been allowed to air dry, but it has been my experience that the rubber might harden up and/or split.

With rubber, probably the first dose of WD sealed off the air gap to the point where the rest might not have done any real good. The best way would be to have a helper spray the mount while you worked the crossmember to possibly flex the rubber enough to allow the penetrant to chase along any opening you may create

I wouldn't keep plowing the WD to them though until your actually ready to pull them out.

I was surprised at how easily the corroded piece of crap I had popped free with only one heavy shot of penetrant and a heavy pry bar working by myself.

As I stated in prior posts, I spoke with a tech. Rep. from Permatex who confirmed that their never seize could also be applied to the rubber mounts without the risk of deterioration.

Good luck with it Mike,

Chuck

[Michael L.]

Re: C3 rear diff crossmember

O.K. I was able to get crossmember off. Both of the bushings are toast. When I replace them on which side do I put the silicone grease or the never seize? Does it go on the part of the bushing that touches the frame or on the part that touches the crossmember?

Mike

[Joe L.]

Re: C3 rear diff crossmember

O.K. I was able to get crossmember off. Both of the bushings are toast. When I replace them on which side do I put the silicone grease or the never seize? Does it go on the part of the bushing that touches the frame or on the part that touches the crossmember?

Mike

Michael------


The lubricant goes on the inside surface of the cushion. Actually, you can put it on the "sombrero" bracket which is welded to the frame and which is the part that goes into the cushion.

[John H.]

Re: C3 rear diff crossmember

Like this - it's a metal-to-metal joint.

[Michael L.]

Re: C3 rear diff crossmember

Thanks guys.