wscuatt

My 95 sport has the craptastic Ax-15(many will argue this). I got her with a bad clutch replaced clutch and for peice of mind had the tranny rebuilt. Skip forward 800 miles and 4th gear and reverse crap out so pull tranny marvel at the bruteness of my centerforce clutch cuase it still looks new then proceed to tear down and rebuild 1000 mile and now same problem. I need some help here as to wtf and if this time I should just scrap ax-15 and put an nv 3550 in

hankthetank

What kind of fluid did you use? Who rebuilt it? Warranty? Ax15's are just as tough as the nv...

wscuatt

I used a synthetic fluid a buddy of mine did it off the clock at his shop he'll help rebuild but thts it its on my dime he has no idea why the parts failed hes used the same supplier for the last 10yrs an as of today the whole trans is goin to hell 1st jumps out with a slam 2nd 3rd an 5th crunch oh yeah 4th just grinds with a whir clutch is mint slave was new at first rebuild and mint so at the cost of a total rebuild I can get a diff trans or should I cross fingers an go at the ax

hankthetank

You can't use newer synthetic gear oil in an ax15. The sulphur attacks the old school brass synchros, 10w30 motor oil or GM/Pennzoil synchromesh is best. I use Pennzoil, shifts like butter. Using the wrong oil should not cause the problems you're having though...could you get another unit at a junk yard? I don't mean to disrespect, but maybe your bud didn't button something up right, and this could be an entirely different problem than you had before...or there is something inherently wrong with the one you just had rebuilt...but then again your transmission guy should have caught that...
You're in a tough spot, I understand, but maybe yeah, start fresh on another one, either way its risky. Unless you got the cash for a reman with warranty!

wscuatt

Ah that could be the problem I had no idea bout the fluids. Im not havein him due the current rebuild as it stands 1500 is shop price for a total tear down an rebuild with a 1yr parts warrenty or 1900 for a fresh reman. Ill know a little more this weekend when I drop it an open the case. Ty so much for the input I will keep you posted as to my findings

wscuatt

And no disrespect at all I know more bout the autos then these sticks

hankthetank

Cool, I'm interested to see how it turns out.

s14unimog

I've had great success with Amsoil 75W-90 GL-4; so I'm going to suggest that.

I've rebuilt my AX before and so I'm familiar with the guts so what sort of damage have you noted in there. I can say if you run them low or even out of fluid (usually by fault of the tail seal) you can damage the forks enough that they won't push the syncro assembly far enough; which produces that pop back grind.

wscuatt

Ok I got her down an apart and its pretty messy in there oil is burt 4th fork is bent reverse is a broken fork an theres missing teeth an a lotta shaveings looks like a total rebuild from here thankfully I have a warm shop to work in an a ride to work

s14unimog

geez man, that blows. Sounds like total carnage. If it helps at all the guys over at Southern Gear in Smyrna GA are incredibly helpful and stock most hard parts for the AX15. I think the replacement fork I got for mine was $34 or something.

wscuatt

Yeah Im gonna weigh the options rebuild or replace I found a rebuilt nv3550 for $800.00 over a rebilt ax15 for $1900.00 and now compileing a price list for a rebuild of this one on the shop bench

5-90

The AX-15 prefers GL-3 gear oil.

Unlike engine oil through API SL, the GL-series specifications are not reverse compatible!

The AX-15 uses bronze synchronisers, and bronze is considered "yellow metal" in the industry. A "yellow metal" is pretty much any copper-based alloy (brass, bronze - even the "red" versions of them are still "yellow metal.")

GL-4 and GL-5 gear oils have increasing amount of sulphur-based EP (Extreme Pressure) lubricants in them, which is why GL-5 is generally required for drive axles. However, the sulphur-based lubricants are naturally antagonistic to yellow metal parts, and will literally attack the copper and dissolve the parts! Ergo, any brass or bronze bushing, synchroniser, bearing, or whatever is subject to attach from GL-4, GL-5, and GL-6 (if you can find it...) gear oil.

Most synthetic gear oils follow the GL-5 specification, just as most synthetic engine oils follow API Service SM specification (meaning you don't want to use those, either. Different discussion - I'll go into it elsewhere if you like.)

There are, however, "performance synthetic" gear oils with the GL-5 specification that do not use sulphur-based EP lubricant additives, and actually are "Safe for use with Yellow Metal." They will specifically state as much on the label and/or in manufacturer literature. Check, but RedLine and Amsoil both come to mind when I think of this. If it doesn't specifically say it's "Safe for use with Yellow Metal," then assume it is not!

I'd be inclined to bet that the problem you had was the synchronisers dissolving - which is the fault of the oil, not the parts.

If the gears have stripped, then that's a bad heat-treatment - again, the fault of the parts, not the design of the box (a similar problem can be found in the Peugeot BA-10/5 used 1987-mid 1988. The BA-10 was originally designed for the Peugeot 505 - which is about a thousand pounds lighter, has half the engine, and one-third to one-half of the torque output at the flywheel. I've had four of those fail on me, and I had one fail when I needed a project for my Materials & Processes class, so I did a failure analysis on it. The problem? The gears were too hard for the application, and did not get tempered after hardening, which is why the teeth stripped off of the thing. The shafts were also hardened too far, and tended to gall in use when overloaded. About the only thing that was right for the application was the case - made from A356 alloy, and actually properly designed for loading to about twice the levels that it was generally subject to.)

I finally got an AX-15 to replace the Peugeot, and haven't had any trouble since. I did finally get an AX-15e (external slave) to replace the AX-15i (internal slave,) because I've never been impressed with "concentric hydraulic slave cylinders" (it was a bad idea when Mazda did it, it was a bad idea when Ford copied it, and the story has not improved with retelling.) I tended to "baby" the Peugeot as much as possible, and I still failed four of the damned things (I finally replaced them after I was taking off in third gear because first had fully stripped and second was at least 50% stripped. Two of them also stripped Reverse. Fifth looked good when I tore it down - only because I never actually used fifth! 31" tyres and 3.07:1 gearing made me cruise at ~1800-2000rpm in fifth gear, which is too low. Cruising in fourth pulled cruising crankshaft speeds up to around ~2300-2500rpm, and gained me about 3mpg doing it...)

Although, it sounds as though you'd gotten shonky parts. TIP: The forks are usually cast, and cast metal has no real grain structure. If you want them to last longer, do this:

- Get about two to three pounds of sand.
- Get a metal box that will hold all of the sand, with some room to spare.
- Put the sand in the box.
- Degrease the metal parts throughly.
- Put the box of sand and the shift forks in the oven.
- Heat to 400-450*F for at least three hours.
- Remove the forks, bury them in the sand.
- Set the box out in the garage on the floor (or other heat-resistant surface,) and leave it there for about a week.
- Remove the forks, clean the sand off of them, and install.

Why? Because castings tend to cool unevenly, which sets up internal stresses. Since cast metals lack the grain structure you'll find in wrought metals, this just makes a bad thing worse. This process will "normalise" the metal parts and remove the internal stresses - and the slow cooling is essential! (That's why you bury the parts in the sand to let them cool.) If you can get the parts up to around 650-700*F it will work even better, but even heating them to 400-450*F (top of the range of most kitchen ovens) will still help mightily!

Don't do this with shafts or gears, since they should already be tempered and you can screw up the heat-treatment on them (which is a process that is a good deal more complex.)

Sure, you can harden a cast part, but it's not generally a good idea unless you're going to forge it (which changes it from a cast part to a wrought part.) Trying to harden a casting can actually backfire on you, and make it more likely to break.

hankthetank

unless you know exactly what kind of metal the shift forks are made of, i wouldnt bother trying to temper them...certain added elements can either reduce the factory temper or embrittle them. Plus, if it has too low of a carbon content (ductility) it cant harden anyways. Dont do this unless you understand at least the basics behind metallurgy and know what material youre dealing with. Please.

5-90

The shift forks in the AX-15 are standard grey (not pearlitic) iron, and respond well to being normalised.

This isn't even a tempering process, since it doesn't get hot enough (to temper iron or steel, you've got to hit 1200-1500*F. Home ovens don't even get that hot.)

All you're really doing is heating the metal up to expand it uniformly, then packing it in an insulator to allow it to cool slowly and evenly.

Likewise, you're not getting it hot enough to add anything (you're not packing it in carboniferous material, and it's not hot enough to foster hydrogen embrittlement,)

The process taking place here is similar to a "little old lady" getting a V8-powered vehicle, and "just driving it to church and the grocery store on Sundays." It gets mildly heated up and is allowed to cool - making a block that's even better for building a hot engine than a brand-new casting. You're just accelerating the process.

Not to worry - I do understand metallurgy, metallic chemistry, solid solutions, amourphous versus wrought grain microstructures, ...

And, it's something I'd suggest if: A) I didn't know it would work, because I'd done it before; and B) I didn't understand what was going on.

I wouldn't sell it if I wouldn't use it myself, I wouldn't tell you to do it if I hadn't done it myself. Just like when I was in management, the general rule of leadership is "Follow me." I wouldn't tell anyone to go do anything I hadn't done myself, and you'd walk in there and see my bootprint in there before you...

hankthetank

How do you know that...and are you willing to put somebody else's transmission on the line...?