LSD Question

LSD Question 1993 Buick Roadmaster 88k Mi 5.7L RWD
Recently on acceleration, the right rear tire spins until I let off the gas a little, but this car has a Limited Slip Differential
so that shouldn't happen. The RR tire is normal, like the rest, and not slick.
It only happens occasionally, on medium to hard acceleration from a stop. Not drag race acceleration, just entering-the- freeway-from-a-stop acceleration.
I checked the differential and it is full to the fill hole, but I have only had the car for 1 month and I don't know what lubricant is in there. Does this condition indicate a failing differential? If so, what is failing, and what actions are possible to treat the problem? New gears? New lubricant? New Rear End? Other? What other checks can I make?
Thanks for any ideas.
Rodan.
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Rodan wrote:

That sounds normal to me. All the GM limited slips I have owned would allow the RR to spin up from a stop. If I was moving 3-5 mph instead and floor it on gravel, I have two rooster tails.
One good test for a worn out locker or limited slip is to jack up both rear wheels and hand spin one wheel. If the other side spins the same way as the one you are hand turning, the limited slip is functioning. If the wheel turns the opposite direction, the limited slip is worn out or not there.
There is also an 'old' trick that is even in my Jeep owners manuals for locking up both rear wheels from a start, no matter if you have an open diff like I do or a limited slip.
When stuck on ice and having the RR and in my case LF tires spinning away and going no place fast while my friends are gong for tow straps, I can give the brake pedal a hard hit while giving the gas a pulse. This loads up the free spinning tire so the torque needed to keep it spinning against the brake pressure equals the torque needed to break the other tire free from the ground, so both tires spin up. My owners manuals say this can also be done by applying the emergency brake but I have much better success with using the brake pedal. It takes practice, but it works very well.
Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 'New' frame in the works for '08. Some Canadian Bush Trip and Build Photos: http://mikeromainjeeptrips.shutterfly.com
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Rodan wrote: ( 1993 Buick Roadmaster 88k Mi 5.7L RWD)
<Question about RR tire spin when car has Limited Slip Differential> _______________________________________________________
"Mike Romain" wrote:
That sounds normal to me. All the GM limited slips I have owned would allow the RR to spin up from a stop. If I was moving 3-5 mph instead and floor it on gravel, I have two rooster tails.
One good test for a worn out locker or limited slip is to jack up both rear wheels and hand spin one wheel. If the other side spins the same way as the one you are hand turning, the limited slip is functioning. If the wheel turns the opposite direction, the limited slip is worn out or not there.
There is also an 'old' trick that is even in my Jeep owners manuals for locking up both rear wheels from a start, no matter if you have an open diff like I do or a limited slip.
When stuck on ice and having the RR and in my case LF tires spinning away and going no place fast while my friends are gong for tow straps, I can give the brake pedal a hard hit while giving the gas a pulse. This loads up the free spinning tire so the torque needed to keep it spinning against the brake pressure equals the torque needed to break the other tire free from the ground, so both tires spin up. My owners manuals say this can also be done by applying the emergency brake but I have much better success with using the brake pedal. It takes practice, but it works very well. ________________________________________________________
Ashton Crusher wrote:
I used to have a 95 Caprice which I think is pretty much the same car. It had the 5.7L corvette engine but I don't recall if it has Limited Slip. I do know that I often accelerated hard in it and never had a problem with rear wheel spin. You say "recently" this happened, does that mean it wasn't doing this before and nothing has changed (that you know of) and now it's started doing it? I had an 88 Caprice that would easily spin the RR, unlike my 95. About the only thing I can think of is that your LSD went bad, you have a spring that cracked and that corner of the car is no longer holding up it's share of the weight, or the tire is worn out even though it might look ok or maybe the colder whether has made the rubber harder and less sticky. ___________________________________________________
Thanks for the insights, Mike and Ashton. My experience with LSDs is that they are there to prevent single wheelspin. I love Mike's ice trick for non-LSD cars. I used it more than once years ago, but in my current advanced age (71) my taste for adventure has faded and I religiously avoid getting into icy situations.
Yes, the Roadmaster is almost exactly the Caprice under the sheet metal. Buick openly calls the engine a Chevy. My use of the word "recently" was misleading because I have only had the car one month, so everything that happens happens "recently". It may have always had this condition.
This 93 Roadmaster has less features that my former 92 Roadmaster. The 93 has mechanical seat adjustments, a manual outside mirror adjustment, and slide-and-fan-speed temperature control instead of presettable climate conrol. Looking up its specifications reveals that LSD was an extra cost option. So my 93 may not have LSD at all, therefore it may be working normally. Anyway, I will spin the rear tires next time I have it in the air.
Thanks again for the comments.
Rodan.
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I used to have a 95 Caprice which I think is pretty much the same car. It had the 5.7L corvette engine but I don't recall if it has Limited Slip. I do know that I often accelerated hard in it and never had a problem with rear wheel spin. You say "recently" this happened, does that mean it wasn't doing this before and nothing has changed (that you know of) and now it's started doing it? I had an 88 Caprice that would easily spin the RR, unlike my 95. About the only thing I can think of is that your LSD went bad, you have a spring that cracked and that corner of the car is no longer holding up it's share of the weight, or the tire is worn out even though it might look ok or maybe the colder whether has made the rubber harder and less sticky.
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Ashton Crusher wrote:

Look on the option sticker for G80. That is the normal GM code for a locking rear. However the G80 does NOT operate like a standard LSD. It is a governor controlled unit. One tire has to spin at least 100rpm faster than the other AND you have to be going slower than 20mph for it to work. They are also known as the "grenade80" because they have a nasty habit of blowing up even when not abused.
--
Steve W.
Near Cooperstown, New York
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