Synchromesh Salad Oil Shearback

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Hi all... I have a 2005 Jeep Wrangler with the Mercedes NSG370 six-speed. I drained the factory mystery fluid at around 10k miles and replaced it with Pennzoil's Synchromesh (MS-9224) fluid per the Chrysler TSB. It's been great for a year and the shift quality has been somewhat improved over the factory fill.

Lately, I've been having trouble with a nasty input shaft rattle when idling in neutral with the clutch not depressed. It only happens under certain conditions: Almost but not fully warmed-up. The roughness of the engine would seem to "excite" the lash in the front-end of the gearbox and it would rattle as if there was a loose bolt hanging out of the flywheel.

I had no idea what was going on with the trans but I do recall the OEM fluid appearing thicker than the 9cSt Synchromesh fluid. I had a hunch that the fluid had sheared-back quite a bit over the last year and become so thin that it couldn't dampen the internals properly.

Acting on this hunch, I drained the Synchromesh and it was pretty nasty. Greyish, with lots of black #@$%! on the drain-plug. I refilled the trans with an everyday 10W-30 and went for a spin tonight. The rattle is about 50% of it's former volume and the trans is smoother and quieter overall. Less whirring when rolling along in 1st with the clutch pushed, and less clunking and banging as the driveline lash is taken-up when transitioning from coast to drive. Amazingly, the syncho action is fine and so is the shift quality. It's a little balky going into 1st and 2nd when cold but this smooths-out very quickly.

Thinking about this transmission and its traditional applications (selected Mercedes C-class, non-US M-class/E-class, Vito minivan, and Sprinter), I'm confident that Mercedes-Benz would never spec a 9cSt fluid for this trans. It's simply too darn loud and clunkety when filled with salad oil!

With all this in mind, I need to get this generic 10W-30 API SL out of there and replace it with a lube possessing an additive package that's appropriate for an MTX. I'd also like to thicken it up just a little bit more to hopefully suppress the last of that input shaft rattle. This 10W-30 is 10cSt versus the 9cSt of the MS-9224 sauce. I'm thinking that a 50/50 blend of MT90 and MTL would yield a 12.5cSt fluid with a strong EP package.

Any suggestions?
 
If you had sludge with Pennzoil, you won't like RedLine MTL.

I do believe that you want a synthetic so look for Torco or Royal Purple. They don't seem to sludge up.
 
After some searching, it seems that many people are running straight MT90 in this gearbox with good results. Apparently this unit is OK with a 15cSt fluid.
 
Don't mess with it!Put Amsoil MTF and live with it.I have over 100,000 miles on my TJ and when I bought it new it had the "marbles" rolling around in neutral since day one.The NV3550 that I have,which is the same tranny in full size Chev trucks, but different than your six speed.The noise is the same.I'll post a link that has a ggod read on the subject.All in all my noise is almost non-exsistant now and the tranny shifts fantastic but the dealer band-aid fixes do more harm than good.The Amsoil MTF fluis is by-far the best fluis for this tranny...I tried em' all.
 
Geez I better start wearing my glasses when posting...spelling
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Depending on the weather(noticed the location), you could probably go thicker without creating the "too difficult to shift when cold" issue that many complain about in manuals.

1st option is just to stick with the Synchromesh. Its a pretty good MTF, not overpriced at local autoparts stores, and cheap enough to change out yearly. And, if you want to thicken it a little, add 10-25% Lucasoil regular or synthetic oil snot.

I myself prefer the straight fills. Redline MTL, Amsoil MTF, and Torco MTF-R are some substitutes.

You can probably step up to a 75w85 but I wouldn't go too thick simply because too many people complain about shift effort. Those 50:50 blends of Redline MTL/MT90, Amsoil MTF/MTG, or RoyalPurple Synchromax/Maxgear are something to consider. And, by looking at the spec sheets, you could probably go 25:75, 33:66, 66:33, or 75:25 ratio depending on the shift feel.

There a some OEM fills in 75w85 available from local dealers like Nissan, Subaru, Mitsubishi, Hyundai.... that can be considered.

Another option if the precisioncrafted Hondacura manual tranny fluid that Idemitsu is whipping up for Honda.
 
Thanks for the input guys. That JeepsUnlimited link is interesting. I don't know if there's a real problem here or just a bad choice of lubricants.

I did a little more research and it turns out that Castrol Syntorq 75W-85 is available in the US under Chrysler p/n 4637579 -- it's for the NV4500's and it's a 12cSt fluid. I think it'll give it a go. "Hey, the parts counter guy told me it was the right stuff -- Now can I get my warranty rebuild?"
 
Quote:


Lately, I've been having trouble with a nasty input shaft rattle when idling in neutral with the clutch not depressed. It only happens under certain conditions: Almost but not fully warmed-up. The roughness of the engine would seem to "excite" the lash in the front-end of the gearbox and it would rattle as if there was a loose bolt hanging out of the flywheel.





Couple thoughts...

I have a NV5600, but had the exact syptoms you decribe...it was the clutch disc. It sounded like marbles rolling around in the tranny that went away when I depressed the clutch. They had a TSB on the 2003 dodge rams for that, and it is slowly coming back. I attribute it to the springs in the clutch hub getting loose and allowing the hole assembly to shake...

Another thing is that a lot of NV5600 owners ran 5w30 synthetic oils (Amsoil comes to mind) with good results...this was before you could buy a aftermarket synchromesh-rated fluid like RL MTL, Amsoil MTL, or Royal Purple Synchromax...

However, I drained my original fill of dodge's Synchromesh at 50k and it was still clean. The PZ I replaced it with made it another 25k and was crystal clear when I drained it...you might have an internal trans problem...if the metal on the mag was excessive. Another possibilty is the PZ has literally cleaned all the deposits in your trans...I would wait to see what the next fill drains like before I get too excited...

steved
 
Thanks Steve. I'll drain the 10w30 sometime this week. I'll run the NV4500 stuff for 10k then reassess the drain plug glop and the fluid color. I suppose I could do a UOA but I don't have a baseline for this gearbox so I don't know that it would tell me much.
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I had similar issues in an 03 NV3500. Changed twice with PZ Synchomesh, but it would fade very quickly. Then changed to the Amsoil Synchomesh and it is still silky smooth over a year later. I would highly recommend that you try the Amsoil.
 
I've heard from quite a few people, even those using it "off-spec," that PZ Synchromesh is fantastic initially but goes down pretty quick.
 
richard, quad4x4 has the syntorq in 2 qt bottles if you wanted to mail order, quite a bit less the the dodge dealer here. GM alsos sells it under it's own part#.
 
Quote:


I've heard from quite a few people, even those using it "off-spec," that PZ Synchromesh is fantastic initially but goes down pretty quick.





It does...starts out really nice and (in my NV5600) goes to average in under 500 miles...

The Amsoil stuff seems to be the best (in my NV5600) to date, but even it is slowly falling in shifting performance at just over 10k miles...I am awaiting bottles from Blackstone to check both my engine oil and the Amsoil MTL to see what is going on...

steved
 
Quote:


What color are the Redline MTL and MT-90 fluids? How about the comparable Amsoil fluids? Thanks!




I know the RL MTL is red, almost like koolaid. The amsoil is typical oil-brown. I know you didn't ask, but Royal Purple synchromax is purple.

steved
 
Just wanted to post a follow-up... I kept the 10W-30 in there for about 1500 miles and it degraded quite a bit in that short time. The neutral gear rattle and the drive/coast "lash clunk" were back in full force.

Before I got a chance to buy the 4874459 stuff, I decided to refill with Rotella T 5W-40 syn. This is a 15cSt fluid and it's an older formulation that I've had sitting around for three years.

It's truly amazing. This gearbox shifts with the teutonic precision that one would expect considering its origin. For the first time ever, you can do a rolling shift into 1st without a perfect double-clutch. Just apply moderate pressure to the stick and it'll drop in when it's ready.

Truly amazing. No rattle, no catchy shifting into 2nd...

I have the 4874459 on the shelf but this stuff is so fantastic that I don't want to drain it! I just wish it had a gearbox-worthy EP package.
 
Quote:


Depending on the weather(noticed the location), you could probably go thicker without creating the "too difficult to shift when cold" issue that many complain about in manuals.



When people talk about bad shiftability in manuals with thick gear oils (like 85W140),do they mean the synchros will not mesh,causing grinding,or that the shifter will simply take more effort to move. I was just wondering because I`ve been thinking about going to a thicker gear oil.
 
...at least it will leave it clean. I was amusing myself thinking about German Syntec 0w-30 in the trans.
 
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