Transmission fluid change incoming... last one 20yrs ago

skiznits

New Member
Joined
Jun 2, 2022
Messages
24
Location
CA
Yep. It's been quite a long time since the manual transmission fluid been changed. Plus there is a trace leak that I see from time to time.

Jeep Solid on YouTube pushed hard for the red line GL4 fluid so I will prob go with that. It's a 91 4.0.

Since I don't know what's inthere currently, after I drain the old fluid is there any risk w the new fluid mixing with the residuals.

I was gonna flush some new fluid thru and out the drain hole to help flush the old but that's probably minimally gonna help clear out whatever in there.

Also does anyone know how much fluid the trans takes.

The right answer is prob to open and reseal but I'm thinking that may be a big task.
 
Last edited:

Gilaguy23

YJ Enthusiast
Joined
Apr 12, 2021
Messages
650
Location
Q town New Mexico
Id drive it to warm it up real good and drain it till every drop is out. No need to flush it IMO. IIRC both the AX 5 and 15 take 3 plus quarts so get a gallon. 10/30 or redline is a personal choice,just dont buy off the shelf 90wt gear oil from some idiot at autozone who tries to convince you its all the same stuff.
 

machoheadgames

Certified YJ Researcher
Supporting Member
Joined
May 19, 2020
Messages
1,371
Location
Dallas, TX
Redline works fine, I've run it in the AX15 for years but next time I am going with Motorcraft XT M5 QS which is a synthetic 75w90 GL4 made by ford/motorcraft and it made my Aisin built Toyota trans shift really well. Toyota folk swear the Motorcraft works better than the Redline in the Toyota transmission, so I have a hunch it will be better than Redline in the AX15 as well.

Gilaguy is right on quantity, buy a gallon or 4 quarts. Definitely don't go with anything GL5. 10W30 is also an option but when I tried it it just didn't seem as smooth. Others say it's like butter for them, so I really don't know why the disparities from one to the next. Aisin specifies 75w90 GL4 so sticking with something in that category will likely have the most predictable results at least. Others have ran ATF as well with no issues. They aren't too picky, just no GL5.
 

ytradio

YJ Enthusiast
Joined
Aug 24, 2021
Messages
149
Location
WV
Redline works fine, I've run it in the AX15 for years but next time I am going with Motorcraft XT M5 QS which is a synthetic 75w90 GL4 made by ford/motorcraft and it made my Aisin built Toyota trans shift really well. Toyota folk swear the Motorcraft works better than the Redline in the Toyota transmission, so I have a hunch it will be better than Redline in the AX15 as well.

Gilaguy is right on quantity, buy a gallon or 4 quarts. Definitely don't go with anything GL5. 10W30 is also an option but when I tried it it just didn't seem as smooth. Others say it's like butter for them, so I really don't know why the disparities from one to the next. Aisin specifies 75w90 GL4 so sticking with something in that category will likely have the most predictable results at least. Others have ran ATF as well with no issues. They aren't too picky, just no GL5.
I have been bewildered by the range of fluids used. From 75w90 a very heavy oil to ATF basically a 10 weight hydraulic oil. But according to those using them, they all work.
 

machoheadgames

Certified YJ Researcher
Supporting Member
Joined
May 19, 2020
Messages
1,371
Location
Dallas, TX
I have been bewildered by the range of fluids used. From 75w90 a very heavy oil to ATF basically a 10 weight hydraulic oil. But according to those using them, they all work.
Yeah, I think it mostly comes down to the fact that it is simply a box of spinning gears and doesn't care that much. As long as the synchros are lubed up, it should be pretty happy in there. Where most of the differences from one to the other would be felt would be weather extremes. I will say 75w90 is not always pleasant on a super cold day, but it's good enough that when you get the trans a bit warm it's back to good.
 
  • Like
Reactions: ytradio