Engine/Transmission (1998.5 - 2002) NV5600 grinding into reverse

[Woodenhead]

Greetings 24V fellas,



When I try to go into reverse 9 times out of 10 the gears grind at won't go in or they grind and go in with a bit of a crunch. The transmission only has about 5000miles on it and was brand new when it was installed.



When I first got the transmission I missed a couple of hard shifts going from 4th to 5th and ended up hitting reverse this may have had negative effects .



I have a 12V but with a NV5600 (6sp) so I figured I'd post here for better response.



Thanks,

Mike

 

[JRagland]

My reverse doesn't usually grind in the since that its full-on metal gears turning that I feel. It does occasionally though, especially reverse. It almost always has some hesitancy with reverse and downright difficult at times. This is not uncommon with this big transmission. There are a lot of threads on this. Some people report amazing improvement with Redline or Amsoil oils. I've never changed mine from the factory.

Overall, I wouldn't be too concerned that you are hurting much.

 

[RustyJC]

Common with the NV5600. If you touch 1st or 2nd before going into Reverse, it won't grind.



Rusty

 

[BigJimDiesel]

I did the same thing to mine when it was almost new. i just do like what was said and hit another gear before reverse to get every thing stoped and it goes right in. been like that for at least 50k and never seen any shavings in the oil. i don't worry about it

 

[Joseph Donnelly]

Fresh lube helps somewhat. Redline MTL gives smoother shifts than the stock type lube.

 

[Silver_Ram]

Every time my 6 speed starts acting up, I change the fluid (Royal Purple Synchromesh) & it shifts fine. It seems this transmission is very, very finicky about fresh transmission fluid.

 

[LKrueger]

6spd shifting

i noticed u have to be patient shifting into rev. if your in a hurry youre gonna

grind a little, does anyone out there know if shifting w/o clutching hurts anything? im able to do this w/o grinding usually,but is somthing that requires a little practice.

 

[RustyJC]

does anyone out there know if shifting w/o clutching hurts anything? im able to do this w/o grinding usually,but is somthing that requires a little practice.

When it's not grinding (or even when it is), if you haven't exactly matched engine RPM with road speed, the synchronizers are having to speed up or slow down the entire engine rotating mass to allow engagement of the next gear. These synchronizers aren't designed to do this - with a clutched shift, they only have to speed up or slow down the input shaft-related transmission bits and the clutch disc. The result is accelerated wear of the transmission synchro assemblies.



Class 8 trucks that are shifted without the clutch have non-synchronized gearboxes.



Rusty

 

[RJPotts]

First of all Rusty is correct.

Reverse is not synchronized, or all of those missed 4th to 5th shifts that grind reverse would engage reverse, and that would be bad.

I usually put it in 5th for a split second then throw it over into reverse, since I've been doing this, I've never had a "grind".

As for the occasional "grind" I don't think it will hurt anything, the old NV5600 has proven itself pretty close to indestructable.

-R. J.

 

[JWBoothe]

The T-18A (old school 1ton truck box) in my '77 Jeep has straight-cut non syncro 1st and reverse that will make the whole CJ shake when try to engage.



I dont know if they are helical cut gears in the NV5600 or what, but there is a BIG difference. The grinding we get is very tame.

 

[Cummins Pilot]

Same deal here, do like everyone says.

 

[Woodenhead]

Many thanks for the info. guys. I've started dropping it into another gear before shifting to reverse and it seams to be working fine. My old 4500 used to drop in reverse fine but 1st was a pain. While I'm sure new fluid would help I can't imagine I should change the fluid yet after only 5000 miles. I also have the filter kit installed, it's probably a good time to pull the filter and see what's in it since it's a new box.



Once again thanks for the info.



Mike

 

[Silver_Ram]

Mike,



My last fluid change was at 8,000 miles right after a 1,000 mile trip pulling my 5th wheel trailer.