Rear End Fluid Change Help Please...

[74bigblock]

K, so I'm getting ready to change the fluid in my rear end. I bought 2 23oz bottles of the fluid, and 1 of the 4oz posi treatment ala Eckler's. How much fluid do I need to put in? Do I need to wory about the posi treatment seeping thru the rear end seals?

Thanks all! Happy Holidays

-Dave

 

[Vettehead Mikey]

Suck the old fluid out.
Pour in the posi additive.
Pour in the lube till it's level with the hole.
Reinstall the plug.
Drive the car.

 

[brusso]

Suck the old fluid out.
Pour in the posi additive.
Pour in the lube till it's level with the hole.
Reinstall the plug.
Drive the car.

With that being said, I'd go with 2 4oz bottles if not 3.

 

[srthom13]

Any comments on using Mobil 1 synthentic gear lube for the posi rear. I have used it on the 66 and other GM posi equiped vehicles and have had excellent results. A little pricey but how often do you do it. Steve

 

[74bigblock]

My buddy used synthetic on his '66 327 vert. His rear end now leaks a little.

What I have been told is never switch to synthetics after a long period without them. They have a tendancy to swell seals and exagerate tears, cracks, etc.

Thanks for the responses!
Dave

 

[curtis]

Some have had problems with the posi clutches not operating properly with lubes other than the GM recommemded stuff. I would go with the GM stuff. They don't tell you to put in stuff that isn't time tested.

 

[drags1998]

Never have seen any type of oil cause an oil leak,( other than penetrating oil)HAHA!!!! I would use M-1 AND the G.M. additive.

 

[JohnZ]

If all else fails, read the directions and use the lubricants the diff, gears, bearings, seals, and Eaton Posi unit were designed, developed, durability-tested, and released with - GM diff lube and GM posi additive.

 

[Dean Barker]

I always have used the GM differential fluid, but things have changed. GM is having problems. They have replaced thousands of 4 X 4 front differentials because they used the wrong differential fluid. I have two Chevy 4 X 4 pickups and the operator's manuals both list part number #1052271 (GL-5) for the differential fluid. I have about two dozen bottles of this fluid on hand and half of them say the fluid is GL-4. I tried e-mailing Chevrolet to find out what is going on and found out nothing, but kept getting refered to my local service manager, who happens to be my nephew. He said all the area dealerships are so fed up with the GM fluid screwup and the price that all are using Mobil 1 75W-90 synthetic gear lubricant with the GM posi additive #1052358. When I changed the rear end fluid in the Corvette, that is what I used. However, I did use the GM transmission fluid when I changed the transmission fluid. I hope this helps clear up some of the confusion.

 

[pws69]

Any comments on using Mobil 1 synthentic gear lube for the posi rear. I have used it on the 66 and other GM posi equiped vehicles and have had excellent results. A little pricey but how often do you do it. Steve

I have been running Mobil 1 Gear with GM posi additive in th rear as well as Mobil 1 in the 4 speed for about 2 years now without any problems or leaks. It definately quieted the trans down a lot also and it shifts far better than before - and no, I'm not worried about the synchros - I know how to shift. I wouldn't go back.

 

[pgtr]

I always have used the GM differential fluid, but things have changed. GM is having problems. They have replaced thousands of 4 X 4 front differentials because they used the wrong differential fluid. I have two Chevy 4 X 4 pickups and the operator's manuals both list part number #1052271 (GL-5) for the differential fluid. I have about two dozen bottles of this fluid on hand and half of them say the fluid is GL-4. I tried e-mailing Chevrolet to find out what is going on and found out nothing, but kept getting refered to my local service manager, who happens to be my nephew. He said all the area dealerships are so fed up with the GM fluid screwup and the price that all are using Mobil 1 75W-90 synthetic gear lubricant with the GM posi additive #1052358. When I changed the rear end fluid in the Corvette, that is what I used. However, I did use the GM transmission fluid when I changed the transmission fluid. I hope this helps clear up some of the confusion.

This is very interesting. As you know 271 should just be plain ol' 80W90 GL5 'axle lube'.

A GL4 will ruin a hypoid in short order as I'm sure you know.

However GM also sometimes recommends 271 for manual transmissions. Is it possible that it is a GL4/5 'combo' lube?

Would you happen have an image of the two labels each saying GL4 and GL5 respectively? That would be interesting to see. PM me directly if you prefer.