Posi fluid

[studiog]

I am closing in on completing my rolling chassis on my 61. Does anyone know if my posi rearend requires any special type of GM posi fluid or are all GM posi fluids the same? Should I dump the old fluid or just top off. The rear end was done about 8 years ago and it has been sitting since. Any and all input would be appreciated. Thanks guys.

 

[JohnZ]

I'd dump the old fluid, add one 4-oz. bottle of GM Posi Additive, then fill the rest of the way with GM Diff Lube; I'd fill it to about 1/2" below the hole until you drive it, in case it chatters and you need to add another bottle of GM Posi Additive. If no chatter, top it off to proper level with the GM Diff Lube.

 

[studiog]

John Z
Great advice... as usual. Thanks.

 

[Toy4Hal]

John Z, I may take that advice as well. I don't know when the dif fluid was changed in my 62.

Is the GM Posi additive readily available at any Checy Dealer or is there somewhere to get this "special liquid"?

Thanks.

Hal

 

[studiog]

John Z, I may take that advice as well. I don't know when the dif fluid was changed in my 62.

Is the GM Posi additive readily available at any Checy Dealer or is there somewhere to get this "special liquid"?

Thanks.

Hal

I found it at my local Chevy dealer here in upstate NY, no problem. They also had the GM gear oil too... expensive though, Over $7.00 for 24oz container of gear oil. Three containers would do it. You might want to start with two and see where you are. It is a clear color as opposed to the honey color of regular gear oil. Maybe JohnZ could tell you if regular gear oil is OK... much cheaper. Auto Zone had there own brand of Posi additive in stock, but I just didn't want to take a chance.

 

[JohnZ]

Any name-brand 75W90 or 80W90 gear lube will probably work fine, but only use the GM Posi additive.

 

[drags1998]

DITTO!!!!!!! And if you think 7.00 a bottle is expensive,try replacing a ring&pinion.

 

[Toy4Hal]

Thanks, Folks!

 

[67Boomer]

Hello. The shop that rebuilt my trans and posi-rearend for my 67 recommended Mobil 1 Synthetic 90 wt gear oil. I specifically asked them, and they told me no additives were needed for the posi when using this lubricant. I have been running this for two years and haven't had the slightest problem. Best of luck to you!

 

[attret00]

I want to replace my fluid. When it was rebuilt a synthetic was put in it and I remember ( I think) JohnZ said synthetics are ok everywhere except in the differential. Can a small hand pump clean out the old well enough to put in GM fluid? This is in a '64 rear. It now has Valvoline syn. in it and every time I go around a corner in 1st. gear I get chatter.

 

[JohnZ]

A suction gun and a length of plastic tubing will get most of it out; then add the Posi additive, then the diff lube to proper level. It's a lot easier to get to if you drop the spare tire tub first. Chattering in 1st gear when turning a corner is a classic symptom of not having the correct lube and additive blend in the diff. I use a bottle and a half of the GM Posi additive when I fill mine; if it still chatters after you get some miles on it, you may need a Posi rebuild.

 

[attret00]

Thanks again JohnZ. I went to my friendly GM dealer and bought all the needed lubes. I asked for GM posi-additive and they gave me Limited Slip Axle Lube Additive. I hope this is the same thing only called by a different name. As always I appreciate your help.

 

[JohnZ]

Yup, they gave you the right stuff

 

[BLACK MOON]

When filling it just don't let that short clear plastic tube come off and go into the chunk. It is a total waste of time trying to fish it out. You have to split the case to remove it. I know thru personal experience. My name should be Murphy with all the stupid stuff that happens to me.

John Z, when I split my unit there was no gasket just silicone sealant. What do you recommend?
Thanks

 

[studiog]

Good point Moon. I had my own clear hose and cut it a bit long so I could hold on to it.

 

[ctjackster]

sounds like you got the right stuff - the little GM bottle of magic potion looks like this:

 

[attret00]

ctjackster, that is exactly what I got from the dealer. Thanks for the picture.