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MrMiyagi 12-23-2009 10:19 PM

Grinding gears?
Hey there,

I have a 2006 6sp. manual TJ with 3.07 gearing, 33" x 12.5" tires and an NV3550 transmission. Lately I've been noticing that I'm grinding gears when switching from 1st to 2nd gear. The clutch is completely depressed and the RPM's are all the way down when the clutch is depressed so I know my cable isn't loose. I'm wondering if running on such a low gear ratio has done any possible damage or negative wear on my tranny that could be causing this.

The gear grinding probably happens 50% of the time when switching from 1st to 2nd. I can usually prevent the grinding sound if I wait about a second or two after pressing the clutch before shifting. I can actually feel something giving resistance to the shift lever when I do this, and lets up after that second or two. I have no gear grinding in any other gear shift or going from 2nd to 1st.

Any ideas...I hope this doesn't sound expensive

rrich 12-23-2009 11:07 PM

Probably not expensive or difficult to fix.

The resistance you feel trying to go into 2nd is the sychros trying to speed up the gear so they'll be at the same speed when they mesh.

It's basically a cone type clutch.

If the fluid is old, or it's not the right stuff, that cone slips too much.
You need to change it.

Go to the dealer and get the recommended gear oil. Use ONLY the factory recommended stuff, don't succumb to advertising or arm chair racers opinions.

No additives either.

The factory that built it knows what it needs.

Drive it a few miles with the new oil before deciding it needs more.

terrible2 12-24-2009 12:27 AM

I took mine to the dealer when that happened to me, dont know what they did but it stopped the grinding and popping out of gears. but also made it harder to switch into gear, felt like they put lubed silicone around the gears...kindaa tight feeling

banjodog 12-24-2009 01:07 AM

i changed my tranny oil today (hehe) and i put in Redline MTL and its awesome, so much smoother (was gunna use mopar exept the stupid jeep dealer didnt have any, of course) its expensive but worth it :) get a bottle pump though ;) oh and make sure u get a 17mm AND a 14mm hex key tip, the 5 speed ones have only 17mm but as i found out today, 6 speed have both,

MrMiyagi 12-24-2009 08:23 AM

I changed out my tranny oil a couple months ago with Pennzoil synchromesh. I looked on the forums and alot of people had used it on my model of transmission. I topped it off but maybe I'll check to see if the fluid is low. The problem was occuring before and after the oil change idea.

Terrible, how much did they charge you?

chucky cheese 12-24-2009 10:29 AM

Same thing here, 6 speed. checked fluid found it was a half quart low. Topped off with
pennz synchro but it still grinds between 1st and 2nd more so when cold. I find let it warm up and after a few miles it smoothes out and I shift it slowly that seems to do the trick.

terrible2 12-24-2009 03:05 PM

under warranty = ) im going to take it to one here to have them deal with it.

rrich 12-24-2009 08:48 PM

As I said, it's a slippery and viscosity issue. Too slippery the synchros slip too much, not enough slippery and the other parts wear too fast. It's a critical balance.
Through the years the transmissions have undergone changes. What was perfect for one year may be terrible for the next year.

The cones have to slip just enough but not too much. For many many years they all used plain old 90 wt. Not so anymore. Using something that the trans was not designed around is taking your chances.

But then, the hard 2nd, 3rd entrance is not always just a fluid problem. Broken or worn parts can be the culprit - broken, worn brass rings (cones), bad synchro hub, springs or clips, even too much endplay in the mainshaft. All can be very expensive, mostly the labor.

Why would they go bad? Could it be from using the wrong stuff, making it harder to shift, leading to parts breakage?

What's that saying - you can lead a horse -----------------.

UNOHwrangler 03-07-2010 11:37 AM

hmm thats funny cause i have the exact to every detail the same problem and i recently pulled my tranny to check it out and i did indeed put some gear oil i found at an autozone... so what saying is if i go to the dealer and replace the gear oil with the factory gear oil should fix my 2nd gear grinding?

rrich 03-07-2010 11:29 PM

No guarantees of course. but it's cheaper and easier than having the trans rebuilt.

Of course it won't repair broken metal parts, but it does let things work like the were intended.

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