Best 10w30 for ax5?

[calvinh]

Alright, so I'm less than satisfied with the shifting of my 130k mile ax5. I swapped the fluid out about 1,000 miles ago with about 2.5qts of MasterPro GL-5 (says on the bottle that it is MT-1, GL-4 and GL-3 compatible so it won't ruin the synchronizers) and 1 qt of Pennzoil Synchromesh because I ran out of the MasterPro.

I did this because I figured the stuff that was in there had never been replaced after 130,000 miles, and I had a long drive the next day so I wanted to make sure I didn't cause any damage.

The stuff that came out when I drained it didn't have much synchronizer shiny metal material, and the magnet had some debris on it, but not anything abnormal.

After the fluid change, it shifted like a dream for about a week. However, I now have difficulty shifting into 5th gear below 2500rpm, and downshifts are getting much notchier. I haven't experienced any gear grinds.

After reading about Synchromesh and manual transmission fluid in general, I learned that not only is the Synchromesh not good for the AX5, mixing different fluids can also be bad for the transmission.

Because of this, I want to drain it again and replace it with some good 10w30 motor oil. I realize Red Line MT90 might be what a lot of people recommend, but I can't justify spending $60 on a few quarts of oil.

Which type/brand of 10w30 do most people use for AX5/15 transmissions? I am from Minnesota (already gets below freezing at night) so is synthetic the best option?

I'd appreciate any experience/advice people have on this.

Thanks!

[neale_rs]

This is the first time I've heard that Pennzoil Synchromesh would be bad for the AX5.  That's what I'm using and it seems to work well.  Other than that, MT90 would be your best bet.

[calvinh]

This is the first time I've heard that Pennzoil Synchromesh would be bad for the AX5.  That's what I'm using and it seems to work well.  Other than that, MT90 would be your best bet.

Do you think it could be the mixing of the gear oil and the synchromesh that is causing my problems? I know that the MT90 would be the best, but its simply too expensive. No retailers near me sell it, and the cheapest online price is about $14/qt.

Pennzoil synchromesh is sold practically everywhere around here for about $7/qt.

So between the synchromesh or synthetic 10w30, which would work better? Would the synthetic oil make a difference in extremely low temperatures? (-10 days are common here in the winter)

[FourbangerYJ]

I'd stick with the Penz synchromesh. Good bang for the buck.
The MT 90 is spendy but how often do you change the fluid in the tranny? Not very often, unless you do a lot of water crossings. I run the MT-90 from Redline. No regrets here.
The synthetic fluids should do better with extreme temps high or low.

[neale_rs]

Do you think it could be the mixing of the gear oil and the synchromesh that is causing my problems? I know that the MT90 would be the best, but its simply too expensive. No retailers near me sell it, and the cheapest online price is about $14/qt.

Pennzoil synchromesh is sold practically everywhere around here for about $7/qt.

So between the synchromesh or synthetic 10w30, which would work better? Would the synthetic oil make a difference in extremely low temperatures? (-10 days are common here in the winter)

The mixing could be a problem.  I'm not an expert but I've read warnings about mixing lubricants (mostly greases actually).

[Bounty Hunter]

Run a synthetic for smooth shifting in cold weather.  Buck up for the MT90, compare it to the price of a rebuild.....

Or find a synthetic synchromesh if you're absolutely too tight.

[calvinh]

I think I'm just gonna run synthetic 10w30... I've searched high and low for MT90 locally, but no one has it. If it doesn't get better, I can always drain it and put in synchromesh later.

[Bounty Hunter]

Many fluids will eat the soft brass synchros.  Whatever gave you the idea you can run an engine oil in the transmission?

[sharpxmen]

there's this rumor going around that the engine oil and the gearbox oil are the same, from what i know they have different additives and the ratings and tests are different. I've seen engines with integrated transmission, nothing over 1 ton empty weight that i know of (2200lbs) though, motorcycles are a common occurence. IMO stick with the gear oil in transmission if they are separate.

I have read people asking on manufacturer forums (Mobil comes to mind) if they can use mobil 1 synthetic instead of 75w90, the answer was to use whatever the transmission manufacturer has specified - ax5 contrary to all the rumors has never had 10w30 recommended.

[grumpygy]

Of all the cars I know of only a MGB uses Motor oil(30 Wt only too) for the trans.  Try gear oil and it completly stops shifting.

[calvinh]

So would the synchromesh be better?

[FourbangerYJ]

So would the synchromesh be better?

That's what it's made for. Lots run it with good results.

[subsonic]

Skip the 10w30.  Go with a product like Pennzoil Synchromesh.

[calvinh]

After reading this: http://www.jeepforum.com/forum/f12/10w30-ax5-ax15-trans-1100022/ and similar threads I decided to go with the 10w30. First impressions are much better cold shifting over the GL-3/synchromesh mix I had in before, and it mostly cleared up my 5th gear issue.

I figure I'll keep the 10w30 in for the winter and then replace it with MTL or MT90 in the spring when I have more money.

[sharpxmen]

i have a decent ax5 for sale so let me know...