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Transmissions and drive-trains Troubleshoot, repair, rebuild.

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Old 02-22-2014, 11:34 PM   #1
Miklo II
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Exclamation Controlled Differential questions

Ive read that these axles and parts are non serviceable. How does this Controlled "mechanism" work and can it malfunction?

I bought a '76 SDV recently. When I test drove it I did a LIGHT THROTTLE (1200 -1600 RPM) burnout in loose dirt just for fun and noticed it had 2 tracks dug instead of one. Ive been unable to find the build sheet with the identification code or look under the axle for it. Earlier today I did a heavy throttle (gas pedal to the floor) burnout in the dirt and there was only 1 track dug on passenger side. I then did light throttle again and the driver side wheel dug less than passenger side. Whats the deal, is the pumpkin damaged? needing fluid changed??
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Old 02-23-2014, 04:04 PM   #2
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LIGHT THROTTLE

Last edited by Miklo II; 02-23-2014 at 04:09 PM.
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Old 02-23-2014, 04:11 PM   #3
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PEDAL TO THE FLOOR
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Old 02-28-2014, 01:20 PM   #4
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Burnouts in dirt mean nothing.
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Old 03-03-2014, 10:52 PM   #5
Miklo II
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^^^^ lol did you do some actual research on that whole "700r4 wont last" propaganda?? yea I guess you still drive 2 and 3 speeds on the street huh. So because of that invalid argument now youve produced another. You see Ive had two '93 firebird formulas and burnout in the dirt with two wheel tracks means it at least limited slip. my 98 suburban I just sold had a G80 LOCKED differential. So please explain how "dirt burnouts mean nothing" lol. if I had a 1970 500ci (550 lb ft torque) in place of my current smogged down 500 ild burnout on the street too.

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Old 03-03-2014, 11:44 PM   #6
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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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Old 03-13-2014, 04:34 PM   #7
Miklo II
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Well, thank you for that life story.

I actually changed the fluid in the G80 suburban differential so i know exactly what your talking about. Never touched took apart of messed with it just seen it. Just for the record this is NOT my first big boat caddy either. I had a 76 Fleetwood Brougham prior to this one.

NO MATTER WHAT, only one wheel peeled on that car and it was the passenger side. even when i got stuck in the dirt only one wheel. Thats a truely open differential. It seems all the De Villes (whether Sedan or Coupe) have the controlled differential. NO ITS NOT A LOCKED DIFF. I found that out long ago.
But with no traction on dirt at full throttle it supposed to be both wheels since that's how the Cadillac manual states it supposed to work.

Now back to my original question: IS THE POSI MECHANISM NOT WORKING AND/OR WHAT CAN I DO TO REPAIR AND OR SERVICE. I have not gotten around to changing the fluid yet. It only has 93xxx miles on it.
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Old 03-13-2014, 04:50 PM   #8
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Quote:
Originally Posted by Schurkey View Post

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.
Im not gonna debate you on this subject any further. OBVIOUSLY the trans builders in whatever state or area you live in are amateurs, backyard junkies or just straight fuckin idiots. And you should know anything under 400 lb ft is not even in the same league as "high performance" lol. Sounds like another company trying to jip people with doggshit products.


Let me spell it out for you plain and simple: A STOCK 700R4 HAS SHIT PARTS INTERNALLY. A "BUILT" 700R4 HAS THOSE SHIT PARTS REPLACED WITH AFTERMARKET PARTS THAT ARE AS TOUGH AS A TH400.


My trans builder out here in Arizona has had absolutely 0.00000 complaints for his builds whether they be on a dragster that pops wheelies or a mild build like my daily driver. With a core just under ONE GRAND. amazing huh?? 700R's have a big aftermarket just like chevy small blocks. Obviously theres not a whole lot of availability where your at. And just for the record my '76 500ci is 400lb at 2k RPM. I wish i had a '70 eldorado 500 in it.
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Old 03-13-2014, 05:42 PM   #9
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A 400 can be built for 1/3 the price of the 700 to withstand the torque output. 700's can be built to also.
I do have a 200R4 that's built behind a 600/600 cad but It's a $3000 trans built to stay together with 800 tq is put to it

Only a burnout on pavement will help to indicate posi or not. Every rear will slip both tires when neither tire has traction.

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Old 02-22-2015, 09:52 PM   #10
Miklo II
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Quote:
Originally Posted by Nashalac View Post
A 400 can be built for 1/3 the price of the 700 to withstand the torque output. 700's can be built to also.
I do have a 200R4 that's built behind a 600/600 cad but It's a $3000 trans built to stay together with 800 tq is put to
I like the 200 trans also, even better OD ratio. Too bad nuthin in northern AZ NV area.
I honestly see this on the forums all the time about price vs price but 4 gears for $900 is too good of a deal to pass up. The 500ci needs to rev low on the freeway.

Quote:
Originally Posted by Nashalac View Post
Only a burnout on pavement will help to indicate posi or not. Every rear will slip both tires when neither tire has traction.
Incorrect. I cant speak for anything other than these cadillac rear axles. My fleetwood brougham spun one wheel on DIRT. passenger side only. No power to driver side. The sedan I had when I started this thread since has been sold and bought an original 58k 1 owner '75 sdv that rips both tires like a G80 chevy axle. I dont mean to argue but back in the day (as I explain to everyone else) GM was NOT all the same. Axles on BOPCad all had their own design.
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