Rear end shudder

We have a '99 GMC 2500 (old style) 350 auto that has started trying to tell us something. Occasionally, when putting it in drive, it acts like the brakes are applied and it takes at least half throttle to get it to move.
Once it does move, it's ok. Observers have told me that when it does start to move, the rear wheels do a lot of shuddering. Every time it has done this, I had just backed a large trailer into it's space. Maybe coincidence? I'm thinking brakes seizing or rear end going bad and trying to rationalize it, but not having much luck. Anyone have any thoughts or experiences with this?
Dave
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If you have the G8o locking diff it may be the problem, look in the glove box RPO tag see if G80 appears. If so try flushing the fluid in the diff, look for any metal, add new fluid reg or syn. 75-90 and keep your fingers crossed, the locking diffs were problematic.

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I would say that Shep has a good idea I would agree with him.

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Hairy wrote:

    A buddy has a 88 or 89 K-1500 with a brake problem. When the truck sits for a few weeks to a few months (its been in stages of body repair for a few years now), the rear brake on the right side will lock up.
    If your brakes get hot enough, it is possible they could lock. Having the run out checked on the drums couldn't hurt, nor would inspecting the shoes & adjusters. Charles
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have you used your emerengcy brake any, it may have not released all the way and is causing your brakes to lock up
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"Hairy" wrote:

Dave
I can only think of a few things. My first guess is that you have a G80 gov loc that is binding and not releasing and when you start out in a turn it binds. The second thing is the brakes are sticking. I doubt it is the bearing in the rear axle because it they where that tight the rear end would have toasted by now. Another thing is that you may be getting tranny shudder/chatter because if you are back a trailer up a incline and you have a fairly tall axle ratio the tranny will get very hot quickly because rev is not as low as first in the 4L80 that you likely have. How big a trailer are you pulling, what is your axle ratio and do you have a aux tranny coolers too?
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Thanks, everyone for the replies. I didn't find G80 on the RPO label. I know brakes can freeze up after sitting for extended periods, but it only sat about 2 hours the last time this happened. Just long enough to load it. Another thing, it seemed like I could back up, just couldn't go forward. I'll let you know what we find when we pull the rear drums.
Dave
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I have a G80 locker in the back of my '86 K5 Blazer...I've had the same problem in the past. Now the G80 is wasted, and I'm waiting on my new axle to arrive.
You want to get that taken care of immediately. I'm driving a borrowed Suburban until I can get my new axle installed.
Don't end up stuck on the side of the road like me!
~JP
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