what kind of transmission oil goes in a 1988 heritage softail 1340cc?

 

I used HD's Formula Plus in the tranny and primary.

 

Tranny , I use Lucas gear oil

 

85W-140 Hypoid gear oil.

 

I use Mobil SHC-630.

 

Redline shockproof

 

Welcome to HDF. You will come to realise that there are more brands of oil than any mere mortal can hope to use in a lifetime! Some are suitable for our bikes and others are debateable. Your choice for any oil in your bike is almost unlimited, so to see discussion on the subject visit the Tech Oil section - but get a long drink first! Or take the easy option and visit your local Harley dealer.

 

Let me add my $.02 worth. I use Lucas Oil Transmission and Diff Gear Lube 75W90 synthetic, in the trans on my 1996 Harley. The brand doesn't matter, but to protect the gears you need gear oil/grease. As old and loose as the transmissions are on a bike as old as ours, 75W140 might be better. Gear oil needs to stick to the gears as they rotate and be thick enough to remain between the teeth on the mating gears so that they are not metal to metal but always have a protective film of grease between them.

 

Valvoline 85W-140 hypoid gear oil. $6.00/qt. at Auto Zone.

I used H-D semi-synthetic transmission lube until they discontinued it.

 

Never had any issues using the oil HD recommends for each hole on my Harley's.