Rear suspension cross member/differential

[Jerry N.]

I am in the process of removing the rear suspension, and the problem is I can't get the rear cross member to come down. The drive shaft and half axles are out, and we removed the 2 bolts on the end of the crossmember. We get slight movement from the rubber bushing, but the crossmember and differential will not come down. Any suggestions would be appreciated. Thanks, Jerry Nutt 31931

[Mike M.]

Re: Rear suspension cross member/differential

You'll have to get one of the Bar Brothers ( crow, pry or wrecking) to give you a hand. It takes a pretty good size bar to pry the X-member 's female from the frame's male. Don't be under the differential assembly when prying--it breaks loose and Mr Gravity takes over.Closely examine the male's bracket where its welded to the frame side rail.the welds are often compromised, especially if it is or was a big block. good luck, mike

[Chuck R.]

Re: Rear suspension cross member/differential

Ok, it sounds like your leaving the spring and diff. connected, so your going to have considerable weight when it breaks free, so like Mike says, be prepared for it.

I would take either two heavy pieces of rope (I'm talking 1/2" or larger) or chain and make two loose loops just inside where each mount is located.

Then (as Mike stated) get a long and strong prybar and wedge it between the frame and the crossmember. Then, douse the upper side of the rubber mounts with PB Blaster penetrating oil or the like and apply a good steady down force with the bar.

Be patient as it might take a few minutes for the oil to work it's magic between the rubber and the mount.

The biggest thing is to be prepared for the sudden release and where you and Mr. bar are going to end up WHEN it does.

The rope/chain will catch the released crossmember and you will be able to then work on releasing the opposite side.

Be sure you wipe the oil off the rubber mounts as soon as you can so that it doesn't degrade the rubber mounts if your planning on re-using them.

Be patient, just work the bar up and down with a good strain on it and it WILL release.

Good luck and be careful,

Chuck

[Steve Vaughan]

Re: Rear suspension cross member/differential

I had good success with removing the crossmember on my 67 by removing the crossmember bolts, replacing with slighly longer bolts with a dimple drilled into the top of the head (to accept puller point) then using a two jaw gear puller to break the arm loose from the frame. This captures the crosssbar when it releases and doesn't require long levers.

[frank mccracken]

Re: Rear suspension cross member/differential

I like the puller idea. I'll look at that tomorrow, I'm doing that job as well. When prying, instead of ropes I've also heard of installing longer bolts to retain the crossmember when it releases.

[Wayne M.]

I'd wory about breaking the nut welds ...

It's only tack-welded to the inside of the "hat". The forces using a puller would be entirely on those welds; if they break, you're in deep doo-doo.

[John H.]

Re: I'd wory about breaking the nut welds ...

I agree - the puller is a slicker approach than the usual pry-bar, but the puller puts a LOT of stress on that weld nut, and if it pops loose, you're in a world of hurt (especially with the body on).

[frank mccracken]

Re: I'd wory about breaking the nut welds ...

I just popped 'er outa there. Prying was bending stuff, so I tried the puller. Worked great. Took your advise tho and didn't get too carried away with the pressure. Question: Can I use anti sieze on re-assembly? Will that damage the rubber?

[Terry M.]

Re: I'd wory about breaking the nut welds ...

Frank,
Anti-seize is a petroleum based product. Any such product will deteriorate rubber over the long term. I would be inclined toward silicone grease, but I have only one vote. Let's see what others have to say.

[frank mccracken]

Re: I'd wory about breaking the nut welds ...

Right on Terry, I've got silicone grease!

[Craig S.]

Re: Rear suspension cross member/differential

Jerry - I fabricated some "catch bolts" when I did my 67, longer than those used to retain the crossmember in the sombrero hats but a safety to catch the assembly when it pops loose. I had my spring removed at the time so it was 42 pounds lighter than yours....Craig

[Chuck S.]

Why Bother With Anti-seize?...

Frank, for this application, I wouldn't bother with any anti-seize.

I believe that GM engineers intended for those end connections to get really tight when torqued properly, because they didn't want them moving around. Besides, it's not like you are going to be taking this cross member off every year for maintenance. Typically, the rear cross member is removed during a body-off frame restoration. In that case, it's doubtful you will ever take it off again.

[frank mccracken]

Re: Why Bother With Anti-seize?...

The cross member comes out for a gear set change, I'm not sure I'm gonna be happy with the 3.36's I'm installing so it could come out again, so I'd really like to know which to use, silicone grease or anti seize.

[Chuck S.]

Re: Why Bother With Anti-seize?...

"The cross member comes out for a gear set change..."

Removing the rear cross member on a C2/C3 Corvette to access the differential carrier must be an old masochistic hot rodder's trick. This technique is NOT in the GM service manual. In this case, anti-seize appears to be a solution in search of a problem. JMHO

[Patrick H.]

Re: Why Bother With Anti-seize?...

It's not in the Service manual, but I've done it this way myself and found it easier, in the long run, that attempting to get at the bolt heads from above which hold the differential to the crossmember. You can't see them, and rarely can feel them, and have no idea how rusted they might be.

It may be easier second time around to try from above, but I doubt it. Rather than silicone or anti seize, I'd run the bolt through a die, and run a tap through the nut. Use some light oil or similar lubricant on the bolt, and reinstall. Odds are that by the time you replace the differential or gears, if in fact you do, the bolt will not be difficult to remove. That is, unless you live in upper NY state and your Corvette is your salty road winter beater. I'll explain that type of car to you sometime, Chuck.

I would use silicone on the rubber sombrero busing as Joe discusses, but not on the bolt, if that might have been your intention.

My friend has a 66 coupe, former drag car, with a nice rectangular hole cut in the floor of the rear of the car, right above the differential attaching bolts. Seems some former owner couldn't figure out how to do it correctly, either.

Patrick