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Old 03-03-2014, 11:44 PM   #6
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Join Date: Mar 2006
Location: The Seasonally Frozen Wastelands
Posts: 439

Burnouts in dirt mean nothing because with enough power and skinny tires, there's enough friction in an open differential to spin both wheels. Been there, done that, enough times to be bored with the process.

You want to know if that differential is a positraction/limited slip/controlled slip unit? You might try jacking/lifting one rear wheel off the ground with the trans in neutral, and seeing if it'll turn. If it won't, or if it's real stiff to turn, it's a posi. If it turns freely, it's probably an open differential.

This is not a positive test. I've got a '68 El Camino with a posi that has lost all it's preload. I'm guessing that the clutches have worn out. One wheel will turn freely in the above-described test--but the vehicle will leave two tire patches on concrete when the throttle is kicked.

The ONLY sure way to know if that's a posi-type differential is to open it up and look.

PS: Too bad you didn't open that 1998 G80 differential to see what "Gov-Lock" means. It's little more than a regular limited-slip/positraction rear axle, plain ol' ordinary clutch-style posi but with a speed-sensing gear/governor system to enhance engagement. Got one of them on my '88 work truck.

PSS: Look up the torque limits of the highest-performance 4L65E in the GMPP catalog. It's under 400 ft/lbs. It takes a mighty lot of expensive aftermarket parts to make a 700 last behind a big-block; and even then it's not going to take 550 ft/lbs in a heavy car with highway gearing for very long unless the rear tires are pathetic. Either the rear tires spin, or the trans will sh!t the bed.

Last edited by Schurkey; 03-04-2014 at 12:04 AM.
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