69 Electra catching in the rear

[Guest my3buicks]

I will ask some of the more mechanically minded people before I tear into this problem - what happens is when I pull out from a stop (not from a straight ahead go but making a left or right such as pulling onto one road from another) I get a grabbing or even a bit of a clank from the rear end. I had thought originally it may have been a brake shoe grabbing but I did a complete brake job on the car last year including wheel cyl and it still does it. I am guessing something to do with the rear end binding? ? ? Something to do with the Posi ? ? ? You can positively feel a catching and then you can hear whatever letting loose and then all is fine - I need to deal with this before it deals with me!! Thanks

[NTX5467]

If the car has a PosiTrac rear axle, it probably needs a fluid change with the correct GM additive added. The earlier PosiTraction units were "locked until they unlock" instead of like the more recent versions that are "unlocked until they lock" and lockup via a governor weight swinging out after one wheel spins a calibrated amount.

On my dad's '69 Chevy pickup, which he bought new, it would do it worse on slow, left turns (similar to what you describe). It would pop and make the pickup jump when it did.

Used to be that GM had a particular part number rear axle lube for PosiTracs, but now all of the lubes are universal. When that happened, the PosiTrac additive became necessary. The "unlocked" style later units aren't supposed to need the additive, but the earlier styles definitely do.

With the new fluid change w/additive, it might help to do some figure 8s in a vacant parking lot to get the new grease worked into the clutch plates. I read that in a car magazine back in the '60s. You might also want to check the condition of the trailing arm bushings too.

Enjoy!

NTX5467

[palbuick]

Hi

NTX 5467 got it right.

Happened to my old 70 Wildcat, Turning a corner i thought the rear end broke, with all the klunking it did. I had to have the rear end cover removed and all old fluid removed cleaned and new fluid and new positraction fluid added. The addative for the positraction used to be called whale oil. You may have to hunt for the addative, don't know if available any more.

Jim Schlf

palbuick

[Guest my3buicks]

Thanks guys, I thought it might be related to the rearend/posi. I also knew it was time to do something about it when my son said "Dad, you ever going to fix that, it's embarrassing".

[JohnD1956]

My local NAPA has this additive, so they claim. I haven't tried it yet, but one of their tenured counter men is my friendly next door neighbor, and I'm pretty sure he wouldn't give me bad advice.

[Guest my3buicks]

thanks John, that will save me some running around I'm sure

[JohnD1956]

Please let me know how you make out. I now have two 69's to do this on.

[NTX5467]

The Limited Slip Additive is still available from GM. Many dealers that used to carry it in the past might not have it now, but it's still around in the same bottle that it's been in for a long time. Seems like the part number is 1052358. If one dealer doesn't have it, they can check on the "D2D Link" locator service or you can check Partsvoice.com too. It, like the Supercharger Oil for supercharged Buick V-6s, might take a little time to track down, but it's still possible to do. Distributor Cam Lube is still in the GM Standard Parts Catalog!

Thanks,

NTX5467