my 91 xj sometimes doesn't like to change gears

Hi i'm new here and I recently purchase a 91 cherokee 2dr 4.0L 4x4 5spd to use as a commuter for winter. its not pretty to look at but when i got it last week it was running perfect. Recently it seems like sometimes when i want to change gears not only will it go into gear but sometimes make a horrible grinding sound. Basically whenever i cant shift it would be from first to second and i would have to shift from first to third. It happens randomly on all the gears. I know for a fact that when i shift into reverse it makes a grinding sound but it still goes into reverse. My mechanic said its probably a slave or master cylinder that faulty and that i should change them both. I checked the clutch fluid and its full and doesn't look dirty. I was thinking about checking the transmission fluid later this week. Does a master cylinder/slave cylinder sound right to you guys and do you know where i can get them cheap cheap?

thanks

First, try draining the transmission of whatever is in it and replace it with a good 10w30 synthetic motor oil.

The original spec was GL-3, but that is hard to find anymore. If it has GL-5 in it, well, GL-5 is NOT yellow-metal safe--yellow-metal as in synchros.

You can buy Pennzoil Synchromesh, $8 in the U.SL; Redline MTL $9.95 mail order (don't forget to add for shipping); Chryco special transmission fluid $20 at the dealer; or just use synthetic 10w30 motor oil, I use Mobil-1 brand but it doesn't really matter.

thanks a lot! i'll check it out sometime this week and hopefully it will fix this problem.

would synthetic 10w-30 motor oil be better of 80w90 gear oil. I was looking at my Mechanics OnDemand software and it said to use 75w-90 gear oil.

skylinergtr said:

would synthetic 10w-30 motor oil be better of 80w90 gear oil. I was looking at my Mechanics OnDemand software and it said to use 75w-90 gear oil.

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If you can find genuine, real, GL-3 75-90 and want to use it, well, that is what was originally specified for the transmission.

When cold, it will shift like crap.

Finding GL-3 is problematic as it is essentially out of production, and the replacements, GL-4 and GL-5 are not for use in the XJ transmission, with a particular emphasis on GL-5 as it will eat the yellow metal synchros.

Pros to synthetic 10w30 motor oil: you can find it anywhere, your trans will shift better all the time, especially in the cold.

Cons to synthetic 10w30 motor oil: none.

joe_peters said:

If you can find genuine, real, GL-3 75-90 and want to use it, well, that is what was originally specified for the transmission.

When cold, it will shift like crap.

Finding GL-3 is problematic as it is essentially out of production, and the replacements, GL-4 and GL-5 are not for use in the XJ transmission, with a particular emphasis on GL-5 as it will eat the yellow metal synchros.

Pros to synthetic 10w30 motor oil: you can find it anywhere, your trans will shift better all the time, especially in the cold.

Cons to synthetic 10w30 motor oil: none.

Click to expand...

thanks, i will definitely do synthetic 10w-30 now. Its getting pretty cold here in vancouver i can understand if its going to shift like crap when its cold. What do you suggest for motor oil? conventional or synthetic? the truck has approx 170,000 miles. Also when switching to 4H the car has to be moving 5mph or less? how fast can you go on 4H? the car does not have a owners manual so i dont know the full operation of 4x4. Thanks for all your help.