So I recently began resurrecting a old friend's 64 J88. He passed away and left it to me. It's a mess. But in trying to do differential fluids, I don't know the first thing about type of lube or where to install. Any help would be great.

 

Use 80-90 weight gear lube. Differential should have a plug on the passenger side that you can use a 3/8 ratchet with or without an extension to open. To totally drain it you should take the back cover off and drop all the fluid.

 

Removing the back cover is the only way to drain the fluid. The plug on the side is a fill plug and the oil level is supposed to be below the plug. When you order a new gasket for the rear cover, your car has an 8.2" BOP axle, which is unique to the J88. Don't expect parts stores or online catalogs to get this right.

 

So you can use a different reference if you want that might help calm down the situation of who is right and wrong at the Parts store...Use F85 or Cutlass 1964 That might help.
Just trying to help.
Jim
JD

 

^^^This. The center section and gears are the same as those in a 1964 Cutlass. So are the brakes. The only differences are the actual housing (which is wider) and the axle shafts (that are longer to match).

 

Ok - So I looked up a Jetstar I and in the Timkin book it have totally different bearings than a 8.2 rear end. SO.... I would really love to see pictures of the rear cover of the Joaey car. If you have time.

I do not think i have ever worked on a 64 65 Jetstar ...
BELIEVE me I know the books are wrong ALOT... i JUST DO NOT LIKE TO BELIEVE TILL i HAVE SEEN. jIM sorry hit the caps keep too many times... lol.
JIm

 

Jetstar I and Jetstar 88 use completely different axles. J88s use the 8.2" BOP axle. Jetstar I for 1964 used the 57-64 Olds/Pontiac 9.3" axle.

 

Ok Well the books have Jetstar one with the WRONG bearings for sure...lol. they are using the same as the 88 1.875 (inner M804049 and the big outer bearing m88048
The book says (exc. Jetstar 1 ) has the 1.438 inner bearing surface diameter HM89449 and the outer M86649 (which are the same as a GTO Cutlas Skylark 8.2 rear.
So they screwed that up...lol. TIMKIN BOOK from 2004

 

SAME book screwed up the 64 65 66 Grand Prix bearings also wrong outers listed. BOOKS... Can not trust them...AS I ALWAYS physically measure stuff and I always want pictures of the rear cover area to ID the rear. Yoke and flange ends. THEN I can be confident of what were dealing with.
JIm