Novak Conversions Jeep Wrangler YJ radiator

YJ Manual Transmission Question

SquareFace

SquareFace

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Joined
May 21, 2025
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Illinois
Hey everyone,

Does anyone out there have silky smooth shifting on their manual Jeep YJ?

I’ve got a 1992 YJ that shifts into all its gears, but honestly, it’s not nearly as smooth as some other stick shifts I’ve owned. For context, I’ve had a 1988 Honda Prelude, a 1996 VW GTI VR6, and a 2010 Wrangler Sahara Unlimited—all three shifted way smoother than my YJ.

In my Jeep, it sometimes feels like the shifter wants to “catch,” and doesn’t quite lock in smoothly. I also occasionally have trouble finding reverse.

Is this just normal for YJs, or is there something I should be looking into? Have any of you managed to improve the shift feel on yours? Any tips, upgrades, or maintenance suggestions would be hugely appreciated!
 
If you have a 2.5l, you have an AX-5 transmission, if you have a 4.0l you have an AX-15 transmission. I've had both and they're not super smooth. They're old-school truck like transmissions. They get into gear just fine, but they have a long throw and plenty of play. Sporty cars, such as a prelude or gti are made to be going in and out of gears often and quickly. The newer jeep has the advantage of 20 years of technology development. For it not going into reverse, if I'm not mistaken, is because reverse gear is not synchronized. Meaning it doesn't have a synchromesh to help with shifting like the other gears. If it doesn't want to go in reverse, just go back to neutral, clutch out for a sec and then try again. If you want better shifting, b&m makes short throw shifters for both tranny's. It'll run you around $400 or so. You could also try running Redline MT-90 gear oil. People say they've had good results with that
 
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Cole Bertelsen said:
If you have a 2.5l, you have an AX-5 transmission, if you have a 4.0l you have an AX-15 transmission. I've had both and they're not super smooth. They're old-school truck like transmissions. They get into gear just fine, but they have a long throw and plenty of play. Sporty cars, such as a prelude or gti are made to be going in and out of gears often and quickly. The newer jeep has the advantage of 20 years of technology development. For it not going into reverse, if I'm not mistaken, is because reverse gear is not synchronized. Meaning it doesn't have a synchromesh to help with shifting like the other gears. If it doesn't want to go in reverse, just go back to neutral, clutch out for a sec and then try again. If you want better shifting, b&m makes short throw shifters for both tranny's. It'll run you around $400 or so. You could also try running Redline MT-90 gear oil. People say they've had good results with that
Click to expand...

Thank you. Was just reading about MT-90.
 
My original AX15 was not great at shifting. Probably because of the GL5 fluid that the factory supposedly incorrectly filled them all with which is not friendly to the yellow metals found inside. I got a brand new AX15 in 2016 and it was much better, to the point where it feels normal and not any better or worse than my much newer 2021 truck’s manual (Toyota - Aisin)

One thing that helps more than you realize is the shift boot, or changing it out for something better. Old ones the rubber gets hard and stiff (giggity), newer ones are better but they still make shifting not as good as it could be. A leather boot makes it much easier to shift. I had leather for a long time but wanted the stock look, so I found a Mopar and went back. However, I’m not loving that decision so much and I may reemploy the leather once again eventually.

Redline is good but I like Driven 80W-90 GL4 better. That is what I currently have in the truck and the Jeep and also the transfer case in the truck.
 
machoheadgames said:
My original AX15 was not great at shifting. Probably because of the GL5 fluid that the factory supposedly incorrectly filled them all with which is not friendly to the yellow metals found inside. I got a brand new AX15 in 2016 and it was much better, to the point where it feels normal and not any better or worse than my much newer 2021 truck’s manual (Toyota - Aisin)

One thing that helps more than you realize is the shift boot, or changing it out for something better. Old ones the rubber gets hard and stiff (giggity), newer ones are better but they still make shifting not as good as it could be. A leather boot makes it much easier to shift. I had leather for a long time but wanted the stock look, so I found a Mopar and went back. However, I’m not loving that decision so much and I may reemploy the leather once again eventually.

Redline is good but I like Driven 80W-90 GL4 better. That is what I currently have in the truck and the Jeep and also the transfer case in the truck.
Click to expand...

Giggidy! Haha! Ok I’ll check out Driven as well and report back. Where did you get your leather boot @machoheadgames ?
 
@machoheadgames I just went down a rabbit hole from previous threads on this forum. Would you recommend 75w90 or 80w90 for gear oil? Redline is 75w90 and Driven is 80w90. (As you probably obviously know)
 
The viscosity really isn’t critical. Either of those will be perfectly fine. I used to like redline but after trying Driven in several transmissions I like it more. Conventional fluids seem to work a bit better in gearboxes than synthetic.
 
My 95 ax5 is smooth like butter. I had it rebuilt about 10 years ago because the previous owner power shifted for several months because the clutch master cylinder failed (dumbass). I run 75W90 in it and change it regularly. I double clutch always when reversing and it goes right in.
 
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My current 95 YJ I can't really count as I installed a brand new AX-15 in it and have run MT-90 since day one. It shifts very smooth and easily. Compared to some performance cars I've had with short throw shifters, it's a lot easier lol.

Machoheadgames mentioned the shift boot. In my previous 91, the shift boot had become as hard as a damn rock and it impacted the shifting to the point of even popping out of gear on it's own. I didn't realize how bad it was until I removed the boot for maintenance and found how much better it shifted when I had the boot removed. I wound up finding another one at a local junkyard that was soft as a baby's bottom lol and swapped that on in it's place. I also dumped the ancient fluid out of it that was god knows what and replaced with MT-90. It wasn't like new again but with those two changes, it became much easier to drive.
 
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Bought my Jeep new in 95 and still own it. Couple of things that have impacted my Jeep shifting gears over the years. Weak or failing clutch master or slave cylinders. Example: A bad master cylinder that isn’t leaking externally, and the pedal still feels strong could have an internal leak and cause a shifting problem. Changing to a lighter weight oil. Years back I started putting synthetic 10/40 motor oil in my transmission. Made a big difference in how my Jeep changed gears. If your Jeep has weak or failing seals, the lighter weight oil may highlight them. My Jeep has over 350k miles on it. There was a point where I had to rebuild the transmission to get the jeep to shift better. Note: Switched to lighter weight oil years after the transmission was rebuilt.
 
Whenever I buy a used vehicle (especially an old one like these YJ's), one of the first things I do is to change out all the fluids and filters. When I first got my YJ it would grind going into 1st and reverse, and wasn't very smooth shifting. I changed out the tranny fluid to Redline MT-90 and it has been smooth and grind free ever since, that was 4 years ago. It's a 93 with the 4.0 and manual AX-15 tranny. I highly recommend it.
 
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I use Valvoline VR-1 10W-30 motor oil and for the rest I use this.
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Novak Conversions Jeep Wrangler YJ radiator
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