thezfunk

I just purchased my first Jeep. 1998 Cherokee, 4dr, 5spd, 2wd, 4.0L, 76,000 miles. I just put in new plugs, wires, distro cap and rotor, air filter, oil change, sea foam treatment, new rear gate pistons, both O2 sensors.

I want to replace the manual transmission fluid and rear diff fluid. I have never owned an automatic and I plan to keep it that way. In every car I have owned there emerged a best manual transmission fluid. One type or brand that seemed to smile on that particular car and bless it with smooth running.

What manual transmission fluids and diff fluids are most recommended? Is there an undisputed champion?

I really don't have plans to use this for anything other than a daily driver. No off-roading or lift kits as of right now.

c-loss

I just run the basic 80-90 in all my manuals and diffs. never had a problem with it.

EndlessMtnFab

I would suggest something like the Redline or Amsoil synthetic fluids for your trans.


While it still uses gear oil .... you are advised to find something with a GL3 or GL4 rating. This mainly has to do with sulphur in the additives for limited slips. Unfortunately, the more sulphur (like a GL5 fluid) the more it "attacks" the brass synchros inside your trans.


On top of that ... few people dispute smoother shifts and less cold morning grumpiness (particularly the 1-2 shift) when using a synthetic.



The downside is the cost .....



We have a few Amsoil dealers on this website including whowey & myself. I'm sure there are other folks who might have access to Redline's products.




Joe

97XJMopar

royal purple all the way around, in my opion Royal Purple is worth it. I used RP in my turbo 1st gen neon, got a extra 4-5mpg a gallon, and the tranny shifted a whole lot smoother after switching to the Syncromax from the Pennzoil version

NewXJaddict

I find it strange that transmission parts would be made of stuff like brass.
Its almost like they design it to fail.

This is somewhat off topic but sometimes my trans is hard to shift especially into first gear other times it shifts just fine. I just replaced the master cyl. Unfortunately I have the stupid BA-10 and no way of swapping in the AX-15 so I am stuck with it for now. Is there a simple way to diagnose what could be the problem with my transmission? I also have somewhat of a grinding noise when driving in 5th gear....I usually only use 1st - 4th but once in a while I get up into 5th gear and it kind of rattles or hums, its kind of hard to describe.

whowey

Except that RP doesn't offer a GL-4 fluid... GL-5 is no-no... for the reason already mentioned by EndlessMtnFab. The sulfur will attack the bronze synchro rings and you will end up with a nice yellow shiny mess in your tranny fluid when you change it.

whowey

Well.... on the bright side... the BA-10/5 uses aluminum in its synchro rings...
But I also wonder if it is done by design.. or if the accountants went on the attack. I had a similar humming in second and third on my BA-10... drained the old NASTY fluid out and refilled it with good fluid and the noise went away. I normally fill through the shifter hole just so I can get a touch more into it.

thezfunk

So I have brass syncros in my '98 Cherokee? My Escort GT had brass syncros and on a strong community recommendation I went with the GM Syncromesh/Syncromax stuff and it worked fantastic. It was weird putting GM recommended fluids in my Mazda transmission but it worked wonders.

I put Redline in my Speed3, again, on community recommendation. It was a huge difference. New shifter bushings and stiffer engine mount also helped but I could tell the difference in shifting after the fluid change too.

I have never tried Royal Purple but I have heard people rave about it. I guess I am not much closer to a decision yet. I do know from experience that the GM Synromesh fluid is excellent with brass syncros and the Redline is great as well.

NewXJaddict

Yeah I already had that done. Unfortunately it didn't help. Oh well I don't use 5th much anyway.

prerunner1982

You would think someone would make an upgrade kit to do away with the brass parts of the AX trans..

jeepride

Redline mtl is what I used in my 97 tj after the tranny failed because of the problem allready mentioned.

whowey

The big concern with Synchromesh fluid is that it is chemistry is much like a motor oil. It has a conventional petroleum base stock and no EP additives like gear lubes. For regular duty it would be fine... But in more rigorous duty like towing, heavy off-roading, or racing it would be susceptible to the same breakdown issues of conventional motor oils.(shear,viscosity runaway, etc.)

thezfunk

Just thought I would post back and let everyone know what I did. I was going to go with the Redline fluid but they don't sell 80w90 that my shop manual tells me to put in the rear diff. In the end, I went with Amsoil. Thanks goes to whowey for helping me to that end. It seems to be working well. I can now get into 2nd much easier on cold starts and overall shifting is smoother. Also the whirring noise from my rear end is greatly reduced at highway speeds.

ZachsXJ

Bad idea, a GL5 rated fluid unless certified to be yellow metal safe will eat the syncros in an Ax-15. Chrysler has started using Mopar 10w30 as a service fill for the Ax-15 transmission, so I would either recommend that or Redline MT-90. the Redline is what I'll be going with when I get around to changing my transmission oil as its designed and rated for gearbox usage and yellow metal safe.

96Cherokee113

Would it be safe to mix 1 quart of Syncromesh and the rest 10W30? I don't have the money to spend on Redline, but would like to have some sort of gear oil in my trans with the 10W30.