Hi all,

I have managed to get back on track with working on my Dynamic 88 as had a few family issues to deal with but thankfully all over. I am in the middle of changing the Exhaust over from a Crossover to a twin system and when underneath noticed the Auto trans pan is leaking like mad, looks like the previous owner went wild with the Silicon sealer but had a NEW filter and gasket from Rockauto. My question being is Dexron ll OK to replace the oil with or does anyone suggest anything different? I have been told to keep away from modern synthetic type stuff. Thanks in advance.

 

What year is your Oldsmobile? Most of the GM automatic transmissions I'm familiar with were designed for Dexron/Mercon III. That being said, I'd be surprised if you could even find Dexron II.

 

Dexron II is long out of production. Dexron III is as well.


Just get this stuff, put it in your transmission, and never worry about it again.

 

My suggestion would actually be to move to a synthetic transmission fluid. Most of these products will handle more heat before burning and maintain viscosity better than the conventional products. That being said, I like the Royal Purple Max ATF and Redline high temp ATF product for these older applications. I have run these products in several old vehicles including a 64 Cutlass with the Jet- Away and my 72 Cutlass with a Turbo 350. My observation is that some people are afraid to even service an older transmission and change the fluid. In fifty years of working on cars I have never had a filter and filter swap lead to a transmission failure!!!

Rick

 

Its a 1966 Olds64, I can still get Dexron II & III here, I remember putting II in my 63 Impala not to long ago. I use a company called Westway lubricants here in the UK https://www.westwayoils.co.uk/search...=1&q=automatic they do a Dextron 6 and if you look still make the II as well, there are so many different types these days.

 

Dexron III is backwards compatible for vehicles requiring Dexron II. Dexron VI is even supposed to be backwards compatible.

The 4T60E in my 96 Oldsmobile 98 died. I tried to swap the filter and flush the transaxle with Dexron VI, but it was too far gone. Can't save them all.

I wouldn't worry about paying extra for Dexron II. Just use the Dexron III. I didn't even put antiquated ATF in the Slim Jim Rotohydramatic that I rebuilt in my 64 98.

 

Please do not put synthetic oil in this trans. Many reasons why. Do some homework if anyone's curious.
Only Dextron/Mercon 2 or 3 or the Dex/Mec.

The fluid leak is probably because the pan is warped from over tightening.
Pull the pan and straighten out the deformations, especially around the bolt holes.
Make sure the trans pan rail surface is free of burs and high spots. Flat file it if needed.

Use spray on gasket adhesive on the pan side of the new gasket. Stick the gasket to the cleaned pan surface. Let it cure.
Assemble the pan to trans dry or apply a THIN coat of black or gray RTV to the trans side of the gasket.
Evenly torque it (NM, lb/In).

If you delete the RTV it will allow you to drop the fluid a few times without having to change the gasket. If there is no drain plug.
I'd do this a few times within a short period to get most of the unknown aged fluid flushed out.
If the pan has a plug use the RTV on the the trans side of the gasket and simply drop the fluid every 15-30km 2 or 3 additional times.

 

Cool you get Dex 2 locally in the UK. I can get mineral or synthetic Dex 3 locally here. As said, make sure the pan is flat and don't use RTV. I assume you have a TH400, get a rigid carrier seal with rubber sealing beads. GM used them factory in later transmissions like my 4L80E, I reused when I replaced the filter. I find old transmissions leak everywhere. Make sure it isn't the dipstick tube or shift shaft seal leaking as well. Good luck from Commonwealth Canada.

 

Type A ATF is still available, though I just use Dex III in all my older automatics. Zero issues. Dex IV and up supposedly have friction modifiers that may not play well with older clutch plates.

 

That one seems to check all the boxes doesn't it. Specifically mentions that it's recommended for Dex III applications.