^ incorrect sir. GL-5 is the only fluid corrosive to yellow metals. 75w-90 GL-4 is what you want. I use/recommend Amsoil 75w-90 GL-4

It's also unlikely that its the fluid issue as reverse doesn't have a blocking ring (what you're calling a syncro)

 

GL-4 is still not recommended for the Asin Transmissions with brass syncro's altho it can be used.

and you are 100% on reverse not being a syncro's gear but 1st is.

the rules for reverse are:

slip into a syncro'd gear before shifting into reverse(i use 4th)
wait 10 seconds with the clutch engaged to slip into reverse
or wait for the shaft to stop spinning.

but having problems with 1st is a fluid issue that can be(most of the time) corrected

 

What's actually weird is that the AX-15 FSM calls for a GL-5 but the statement that a GL-4 is corrosive to yellow metals is simply incorrect. I use GL-4 is all of my Japanese manual transmission (miata, 240sx, Jeep) and even my 1962 Unimog; which I don't have anymore.

The reason why we go to a syncro'd gear is b/c we're using that blocking ring to stop the input shaft. The reverse gear engages the outside of the 1-2 syncro sleeve and is the ONLY gear that actually meshes together when selected. Here is a picture of my AX-15; I just rebuilt mine. The reverse gear is straight cut and at the bottom, against the intermediate plate, on the short shaft.



I know that first is, but if he is having an prominent engagement problem with reverse and some with the other, its likely that the clutch isn't disengaging completely b/c reverse will not engage well with a rotating shaft since it does no have a blocking ring.

 

what year FSM? they changed mid way through the first ones were correct the second ones were incorrect.

but you sir have provided very good information.

 

Thanks! This is the one I always reference; couldn't find a print date. The lubricate information is listed on the left hand side of the second page.

http://www.billhughes.com/temp/AX15.pdf

 

I can pull out mine and see what year it was from (i have years 88-00)

the earlier ones are correct (this a 97 btw)

Looking through my manuals that doesnt appear to be out of any of the JEEP FSM's that I have.

 

just for comparison here is a 97 FSM compared to the same page as yours....

 

AH HA! I found it. between 91- and 95 is when they had the FSM incorrect. 96+ they fixed it.

here is shots out of the 91-95

 

ya, that's weird it's all over the place like that. Hmm... We might just start confusing everyone, lol!

I'm sticking with my Amsoil since I've had such a great experience with it. I know that the 240sx and miata I have both ask for 75w-90 GL-4 and they have yellow metal blocking rings. When I rebuilt my transmission, about 1000 miles ago, it was under a qt. (due to a failed rear seal, and blocked weep hole) with who knows what, and had no damage to the blocking rings; turned out to be a worn shift fork. So I'm sure more than a few types work well in there. I will say that Amsoil is about the only thing that survives in my 240sx as its producing around 400whp and is used primarily on the track.

 

I like amsoil we use their product in the shop. (motor cycle shop)

I have had used Redline in my ax-15 and love it and use Amsoil in others. I just feel better with redline MT-90 is all.

OP either way just dont use a GL-5

 

Why do you call synco's blocking rings? It makes me think of something way different lol. And your both worng, you need to use 10w-30 motor oil I kid i kid. I have an old junkyard trans that didnt shift that great (worn synco's in 2nd and 3rd causing grinding and I'm too lazy to double clutch) and some good ol' fresh gear helped alot.

I think the OP's problem sounds more clutch issue than fluid problem. idk how long the PO owned this jeep but it happening out of the blue makes me think a hydraulic or clutch issue.

 

It's b/c when I was rebuilding my transmission I called everyone I could, to learn as much as I could, and everyone that dealt with the parts seemed to call them blocking rings. I think its b/c a synchronizer is an assembly and that specific component just isn't called that. Funny man with 10w-30, these aren't civics, lol.

I agree with you and 96_xj, it's likely a clutch hydraulic issue, especially considering reverse gives him the most trouble

 

My fuel pump went out and now that I have 3 tanks and pumps out of parts jeeps that dont work I did a VIN number look up and its a 92 not a 93. I still dont have the right pump and havnt been able to drive it to try any of the tricks. Thanks for all the help with it tho. this is my forst jeep and It's been a learning curve haha. I'm good with all the suspension and motor componets all this tranny stuff is new to me tho.