90 Heritage Transmission

[72fl]

I need help with locating the drain plug on a 90 Heritage Transmission, I looked in the usual place between the shocks, Nothing there. Then there is a I believe a Torx head plug behind the exhaust under the Transmission cover, is this it ? What is the Suggested Transmission Fluid to use in this era of Bike ?

I drained the Engine Oil as the Bike has sat for a while, How do I know I got it all out of the Bottom of the case is there a way to or process I need to do ? Should I use Conventional or Synthetic ?

Lastly the Primary what Oil should be used in there and Amount ?

Thanks, Dave

[Hossamania]

Yes, that little torx plug behind the exhaust is the transmission drain. Replacement fluid will be any good GL5 gear oil, I've used Bel Ray and Spectro 75/140, but a lighter weight will work.
If the bike was not started before the oil was changed, there may be an excessive amount that drained into the motor that was not returned to the tank before draining. If you have not pulled the filter yet, put a quart in the tank, start the motor and idle it for a minute, and let the oil return to the tank. If the filter is changed, remove it, pour some oil into it before starting it to help pressure build quicker.
Standard Dyno oil will be fine.
Formula Plus primary oil will work fine in the primary. Not sure yet on capacity, probably 32 oz., but info forthcoming.

[Fugawee]

The Torx Head that You mention behind the Exhaust should be the Transmission Drain Plug.
I have used Bel-Ray 85/140 Tran Fluid in an 88' FLSTC, and a 94' FLHTC.
Approx. 24 ozs.

I would run the Engine for a while to circulate the Oil, then Drain and Replace.
I still use Conventional 20/50 Oil in those years...but what type You use is Your choice.
I have never used Synthetic 20/50 Oil in those due to HD stating not to use it back in the Day...because of the possibility of Oil Leaks switching from Conventional to Synthetic.  I didn't need the hassle.
There is a difference between an EVO and Twin Cam Oil Filter...So, You may want to make sure that You are using the correct one.
I have stayed with Conventional with no issues.

The Primary should take 1 Quart of Fluid.  Maybe a little bit more.
As far as what...I use Spectro Primary Fluid.

You may get a Variety of Responses as to what Brand Type of Fluids others use.
But the above has worked out for Me.

[Hossamania]

If the oil was drained before starting the motor and letting it run for a bit, do not put 3 quarts back into the tank, it may be overfilled when the engine starts and returns the oil. Install one quart, start the motor, then drain and change.

[72fl]

All's well Thank you guys