I know but superseded fluids are not always backwards compatible. My last vehicle spec'ed Dex 3 which was changed to Dex 6 and it wouldn't take any forward gears until the Dex 3 was reinstalled. Plus each transmission responds different to the same fluid.

 

Then note this.

My 1988's 3 speed was rebuild in March; it's running ATF+4.

Yes, the shifts are firm; especially when towing, that's A Very Good Thing because soft shifts are due to it hanging on the clutches longer (!!), NOT a good thing.

But do what you want; it's your truck, your money.

RwP

 

Mine has firm shifts with Dex fluid and has soft shifts with ATF+4.

 

oops wrong thread