Grinding into 3rd and 4th gear

[MHowell]

NV5600. When shifting into 3rd or 4th gear upon acceleration, I will get some light and very short lived grinding until the shifter slides into the gear. It doesn't do this going into 5th or 6th.



What should I be looking for in order to fix this before it becomes a REAL problem? thoughts?

 

[B.G. Smith]

I would guess the synchronizer rings are worn in those gears. bg

 

[TBartlett1]

My NV4500 in my 1990 started to grind slightly as the miles accumulated so I started double clutching to nurse it along. Currently 3rd syncro is gone and 4th is a bit weak but I've adapted as it progressively got worse. I've gotten dam good at it. You just need to take your time shifting.

 

[MHowell]

If it is the synchros going bad, I assume that is not an easy/cheap fix.

 

[HBarlow]

Assuming that you understand that it is a heavy duty light truck transmission and shift it slowly, if it grinds the synchronizers are probably worn. You're correct. It would not be cheap or easy to replace the synchros. Labor to R&R the transmission would not be cheap and the transmission would have to be disassembled just to replace the synchros. Probably wiser to learn to shift slowly and match engine speed to road speed for each gear as you shift.

 

[B.G. Smith]

If it is the synchros going bad, I assume that is not an easy/cheap fix.

I think you are correct on the neither cheap or easy fix. TBartlett1 makes a good point, your timing on shifts may be a little off which caused the synchro wear in the first place. Try slowing your shift sequence just a heart beat and see if you can come up with a smoother engagement. If you are coming down through the gears for braking purposes the double clutching would be necessary. bg

 

[TBartlett1]

Its not just the syncros that would need replacing but there are updates which require new expensive parts, plus bearings and anything else needed for a quality rebuild. Has anyone had a NV4500 or 5600 rebuilt & updated? What was the cost for parts and labor. ANYONE???

 

[steved]

When was the last time you changed fluid?

Mine will "grab teeth" between shifts when the fluid needs replaced... which is about every 20k (or less) for me. I have found my NV5600 tends to shear fluid, which causes it to thin out slightly... the trans then starts getting notchy, and harder to shift without "catching" gears.

Might be worth the $25 in oil to see if that helps the issue.

 

[MHowell]

I just wanted to post a follow-up. I changed the fluid in the transmission. The fluid was real cloudy and sort of grey. Plus I only got 4 quarts out of it. I was able to squeeze 5 quarts of Penzoil Sychromesh back into it. I took the truck out and tried to get the gears to grind again by shifting it hard and fast. Couldn't get it to grind. What a relief.

Having said that, I will start to shift it a lot easier as others have stated previously. I'll try not to make the synchros work so hard in the future. I do drive a manual transmission smaller car from time to time as well, so going back and forth is tough sometimes. I know I have been pretty rough on the NV5600 as far as shifting quickly through gears.

Thanks for all that posted help.