Primary fluid
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Joined: Feb 2017
Posts: 98
Likes: 21
From: Washington state
Primary fluid
I recently did my primary chain adjustment and noticed some tint to the fluid. Scheduled fluid change per fsm is 15000 miles. Silvia is at about 16000. Im sure the PO didnt change it due to the color.
I want to change the fluid. The fsm calls out the specific fluid part number. I googled it and came up with a 75-90 gear oil for limited slip differentials.
Would i be okay running this fluid? Or would you guys recommend that i stick with the hd brand? (And certainly pay more)
Also fsm says it holds 32oz. Do you guys just pour the whole jug in or just enough to touch the bottum of the clutch pack?
Thanks in advance.
I want to change the fluid. The fsm calls out the specific fluid part number. I googled it and came up with a 75-90 gear oil for limited slip differentials.
Would i be okay running this fluid? Or would you guys recommend that i stick with the hd brand? (And certainly pay more)
Also fsm says it holds 32oz. Do you guys just pour the whole jug in or just enough to touch the bottum of the clutch pack?
Thanks in advance.
Club Member
Joined: Feb 2007
Posts: 16,320
Likes: 306
From: Boynton Beach, FloriDuh
I've used Mobil-1 75-90 GL-5 GEAR OIL without issue for over 100,000 miles, you can get it at most auto parts stores. I just pour in the whole quart through the primary chain inspection cover.
Road Warrior
Joined: Sep 2016
Posts: 1,634
Likes: 578
From: Cape Coral Fl
Hey C. You go above the bottom of the clutch pack?
Stellar HDF Member
Joined: Aug 2009
Posts: 3,212
Likes: 212
I do the same as CHarley, and in the times I've had the derby cover off I checked the level of the oil. It's spot on where the factory wants it. You can safely dump the full quart in the sportster trans. without worry on drain/fill intervals. If you've cleaned out the whole transmission/primary dry it takes slightly over a quart to fill to the proper level.
Last edited by Scuba10jdl; Jul 11, 2017 at 04:31 PM.
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Road Captain
Joined: Nov 2015
Posts: 528
Likes: 140
From: Anaheim, CA
I do my primary like once every 2 oil changes. So around every 8K miles. Local chopper shop sells the Spectra stuff so I use that. I've also used the RevTech stuff which according to the label says it's "specially formulated for Sportsters"...whatever that's supposed to mean lol. I used to use that 80-90 (I think that was the weight) Mobil 1 gear oil they sell at Walmart. Same **** you use in rear diffs.
Only difference I've been able to spot is that the gear oil smells worse than the other 2. I wouldn't sweat it too much. I always dump the whole quart in there.
Only difference I've been able to spot is that the gear oil smells worse than the other 2. I wouldn't sweat it too much. I always dump the whole quart in there.
Tourer
Joined: Oct 2016
Posts: 297
Likes: 19
From: Central CA
Prefer Red Line 75W90 gear oil. All RL oil is synthetic.
There is some discussion about the transfer oil through the crank shaft seal between the engine reservoir and the primary/trans reservoir which would enforce the argument to go 20W50 synthetic motor for both cavities.
The trans does not require extreme pressure additive like differential gear oil does with the hypoid gears.
Straight cut gears have less shearing action than helical cut gears on 2008 & up XLs.
Still have an issue using motor oil in the trans.
The primary chain/wet oil is used primarily for cooling, not lubrication.
The forum vote on the H-D big twin trans shows Red Line shock proof the winner.
Unfortunately, unable to use this oil in the XL.
There is some discussion about the transfer oil through the crank shaft seal between the engine reservoir and the primary/trans reservoir which would enforce the argument to go 20W50 synthetic motor for both cavities.
The trans does not require extreme pressure additive like differential gear oil does with the hypoid gears.
Straight cut gears have less shearing action than helical cut gears on 2008 & up XLs.
Still have an issue using motor oil in the trans.
The primary chain/wet oil is used primarily for cooling, not lubrication.
The forum vote on the H-D big twin trans shows Red Line shock proof the winner.
Unfortunately, unable to use this oil in the XL.