AX-15 fluid

How's the Pennzoil syncromesh fluid work in the AX-15? Bottle says that it is direct replacement for Mopar and all tranny's with brass syncros. That's the only oil that I could find at the local parts store that wasn't gl-5. I need to run this for a couple tankfuls, then it's time to put new in again.

I've seen posts from people that used Pennzoil Syncromesh Fluid and said they like it.

With the name "Synchromesh" I have to believe it has friction modifiers in it for the Synchros to engage quickly and smoothly.

I don't understand what you saying about a couple of tankfuls? How does tanks of gas have anything to do with the transmission fluid?

Rick Anderson said:

I don't understand what you saying about a couple of tankfuls? How does tanks of gas have anything to do with the transmission fluid?

Click to expand...

hes refering to putting miles on the trans

Yup, the mileage...

So far it's not doing too bad, tranny issue is going away, but not gone. I'm thinking that all the flush/fluid change has done is buy the tranny more time. Guess I need to really think about whether I want to track down a '00-'01 nv3550 to swap into the '90.

I usually use Sta-Lube (you can't find any locally?) My local carries GL-3 and GL-5.

A synchroniser is a mechanical device, but doesn't depend on cluches - therefore, doesn't require friction modifier. The main issue with GL-5 is that the added sulphur and the heat of operation will work together to dissolve the sintered bronze synchroniser rings.

Granted, I woudln't use Pennzoil in a lawnmower, but I've had too much history with it in engines to like it. It would probably be less problematic in a transmissions, but you'll want to run some solvent when you get some new oil to clear it out.

Since you're planning on replacing it anyhow, is it internal slave, or external? I'm digging around for an external slave front end for an AX-15 (bellhousing, fork, front bearing retainer...)

I would agree NOT all Synchronizers require Friction Modifier, and especially the AX-5/AX-15 that regular GL-3 Gear Lube is recommended.

However, Synchros are made of different materials and produce different level of friction. There are many Manual Transmissions used in other vehicles that have synchros in them that do require friction modifier to work properly. If you use straight Gear Lube or Motor Oil in these trans (that recommend a specific fluid with Friction Modifier) the shifting can be extremely poor, maybe even grinding and damage to the trans. Again, thats NOT all Manual Trans, and definitely NOT the AX-5/AX-15 that GL is recommended.

We could have a long academic argument about Synchros being a form of a clutch, that is really here nor there. There are a friction device and thus fluid properties can have an effect on them. Many large brass and bronze syncrhos work just fine without friction modifier, smaller synchros or ones using organic clutch materials do need the friction modifier. Many trans list the parts of their synchros with the word "Clutch" in the nomenclature, i.e. clutch cone, etc.

5-90, sorry, it's an internal slave...