Engine/Transmission (1998.5 - 2002) NV5600 & Synchro's

[Gary - K7GLD]

I had an interesting conversation with an oil guy (who knows more than I do)... he thinks that overfilling the NV5600 is causing "hot parts" (bearing and gears) to recieve more lubrication and cooling from the oil. And that is what caused my guage to read hotter! It makes sense to me, so I'm going to overfill again on this attempt.

Interesting subject - especially with the related lube level issues the G-56 had/has. I have always slightly over-filled my 5600, but only by about a pint - as much extra as I could get in by parking the truck on a slight incline



When you speak of overfilling yours, what amount of overfill are you considering?

 

[steved]

Interesting subject - especially with the related lube level issues the G-56 had/has. I have always slightly over-filled my 5600, but only by about a pint - as much extra as I could get in by parking the truck on a slight incline

When you speak of overfilling yours, what amount of overfill are you considering?

When I noticed the increased temps, I had stuffed an extra 1. 5 quarts into mine... now that I have the fast coolers, I might just fill it level with the top of the PTO covers... IIRC, the fill plug is about 2/3 the height of the PTO cover (on the side of the transmission looking level)... with the fast coolers, it's difficult to say XX quarts...

steved

 

[Gary - K7GLD]

When I noticed the increased temps, I had stuffed an extra 1. 5 quarts into mine... now that I have the fast coolers, I might just fill it level with the top of the PTO covers... IIRC, the fill plug is about 2/3 the height of the PTO cover (on the side of the transmission looking level)... with the fast coolers, it's difficult to say XX quarts...



steved

It requires lots of faith in the input/output shaft seals to overfill that much - sure hate to have the front seal seep enough to wet the clutch - but then, I'm not sure how deep the seals run in the lube with normal lube levels...

 

[FLynes]

I'm pretty loopy-eyed from reading all of these posts (which I find fascinating, by the way). My NV5600 is making a whirring noise at idle, in neutral and with foot off clutch... . noise goes away when clutch is engaged. The tech says my intermediate shaft bearing on the input shaft is going. I wonder if maybe the wrong fluid was added by the last owner (pipe dream, I know). Do you think that changing the fluid out with Amsoil 5W30 MTF and adding a bottle of Mopar LSD additive would help, or should I just suck it up and have the stealership redo my transmission under warranty? I'd rather not be without my truck for a few weeks. Thanks for the input.

 

[steved]

It requires lots of faith in the input/output shaft seals to overfill that much - sure hate to have the front seal seep enough to wet the clutch - but then, I'm not sure how deep the seals run in the lube with normal lube levels...

At the same time, that seal has to hold in oil within the transmission... if it didn't it would leak... I would be more concerned about an oil seal leaking due to a blocked vent than it being submerged in oil... if that seal will hold back oil now, it would also hold back oil if it was submerged (within reason, very little pressure)... case in point, I have a mower deck gearbox with a seal very similar to those on our trans... it has oil sitting on it. Or even vertical shaft engines. See my point? They don't make one seal for "splash lubrication" applications and another for "fully submerged" applications... as long as the seal isn't forced to hold back pressure, it should be fine!



I'm not to concerned about the clutch at this point... at 112k and knowing there has been something wrong with it since I bought the truck new... it would just give me a reason to change it... So if I'm wrong... WHEWHOO!!! NEW CLUTCH FOR ME!!



steved

 

[steved]

I'm pretty loopy-eyed from reading all of these posts (which I find fascinating, by the way). My NV5600 is making a whirring noise at idle, in neutral and with foot off clutch... . noise goes away when clutch is engaged. The tech says my intermediate shaft bearing on the input shaft is going. I wonder if maybe the wrong fluid was added by the last owner (pipe dream, I know). Do you think that changing the fluid out with Amsoil 5W30 MTF and adding a bottle of Mopar LSD additive would help, or should I just suck it up and have the stealership redo my transmission under warranty? I'd rather not be without my truck for a few weeks. Thanks for the input.

Fluid changes will not help a failing bearing... wishfull thinking though...





IMO, I'd probably suck it up and find an already rebuilt trans and use your's as the core... even under warranty...



steved

 

[AOsipower]

Im gonna try the additive in my truck, next fluid change and see if it shifts any better, Ill let you know...

 

[steved]

CRC's LSD additive did nothing in mine... I still have it in. I figured if it actually did something, it should show in mine now since the Amsoil has started to shift poorly...

I had the best results with Lucas' transmission additive... I may revert back to Lucas and Redline MTL if the MTL/MT-90 mix doesn't work...

steved

 

[DMather]

OK, dumb question. Which way is the dodge friction modifier moving the lube? Does it make the transmission fluid MORE slippery (less friction) or ADD a bit of friction?



I just changed the transmission fluid and what came out was well sheared... ran like water... no slippery at all. Reverse had become impossible from time to time.



With the new fluid everything is starting to return to normal as the fluid works itself in.



When the transmission is up to temp the gears get a bit stiff so I've been debating on trying the modifier... . hesitating because I've had no problems using stock fluid for 340,000 miles.

 

[steved]

OK, dumb question. Which way is the dodge friction modifier moving the lube? Does it make the transmission fluid MORE slippery (less friction) or ADD a bit of friction?



I just changed the transmission fluid and what came out was well sheared... ran like water... no slippery at all. Reverse had become impossible from time to time.



With the new fluid everything is starting to return to normal as the fluid works itself in.



When the transmission is up to temp the gears get a bit stiff so I've been debating on trying the modifier... . hesitating because I've had no problems using stock fluid for 340,000 miles.

Might consider adding some Lucas as it seemed to do more good at hotter temps... I have had no improvement with LSD modifier.



steved

 

[getblown5.9]

i liked the way mine shifted with Redline and dodge FM... but 2 weeks after i put it in i broke the transmission. maybe it was too slippery because i pulled it into 6th too fast and it went grind, bang pop. it would then grind into 6th every time, and the next day i was in 6th and gave it a little gogo pedal and it popped. No more 6th, been driving a NV5500 5 spd ever since

 

[Texas Diesel]

i liked the way mine shifted with Redline and dodge FM... but 2 weeks after i put it in i broke the transmission. maybe it was too slippery because i pulled it into 6th too fast and it went grind, bang pop. it would then grind into 6th every time, and the next day i was in 6th and gave it a little gogo pedal and it popped. No more 6th, been driving a NV5500 5 spd ever since

So you swapped in a 5 speed?

 

[JKinney]

So you swapped in a 5 speed?

I think what he is saying is he has the all new nv5500 5 sp. That was custom built due to 6th gear MIA.



My nv 5600 shifts great, I use amsoil and change it evry 20,000. My only issue is my rear seal started leaking. So I dropped the transfer case, changed the seal and it started leaking again two or three weeks later. Maybe I screwed up installing the transfer case and damaged the seal. What to do let her drip or pull the transfer case... .

 

[Texas Diesel]

Got it :-laf



My mechanic at the Dodge house told me he PO'd the Chrysler rep one day by telling him that thet need to change the 30,000 mile service procedure to include "change the 6 speed". This was back in 01 when they had all the NV5600 problems.



I didnt realize that a 6 speed had some sort of 6th gear problem.



Thanks for the answer.

 

[steved]

Got it :-laf



I didnt realize that a 6 speed had some sort of 6th gear problem.



Thanks for the answer.

From what I have read, the NV5600 is just as suseptable to losing 6th as the NV4500 is to losing 5th... the only difference is the NV4500 has a nut back off while the NV5600 tends to strip the splines from the shaft.



Both are caused by the "bump-bump-bump" vibration the engine places on the drivetrain at lower RPMs... most of the NV5600 failures I have read about were on trucks towing extremely heavy in 6th (I'm sure this isn't all inclusive though).



steved

 

[Gary - K7GLD]

From what I have read, the NV5600 is just as suseptable to losing 6th as the NV4500 is to losing 5th... the only difference is the NV4500 has a nut back off while the NV5600 tends to strip the splines from the shaft.



Both are caused by the "bump-bump-bump" vibration the engine places on the drivetrain at lower RPMs... most of the NV5600 failures I have read about were on trucks towing extremely heavy in 6th (I'm sure this isn't all inclusive though).



steved

I've never heard of gear or spline issues with the NV5600, but HAVE read several reports of bearing issues on the 6th gear shaft, which are supposedly too light a duty for the use of 6th gear in heavy towing situations. Basically, it's suggested that 6th gear - overdrive - be used when the truck is empty or lightly loaded, but other than flat ground with no significant headwinds when heavily loaded or towing, especially in the hills, 5th gear should be used.



This seems another case where the bottom end torque of the Cummins gets other parts of the drivetrain in trouble - the engine makes lots of torque down at low RPM, and seems to pull a decent load OK in 6th gear, but that gear and related components are under stresses they were not really designed to handle. That plus the jackhammer-like wide spaced firing impulses of the Cummins are just too much for 6th gear components when the truck is heavily loaded at lower RPM.



I used to tow our 5th wheel up the long, straight - but steep - Sierra grades in 6th gear too - especially with my mods, the engine was doing fine, speed and RPM were decently up (I figured!) but the transmission probably didn't like it! Since then, and especially after switching to 285 size TOYO tires, I now drop down to 5th in any significant grade when towing, and the engine is right in it's sweet spot for power at 55 MPH with plenty of useful RPM to spare - and I'm sure my transmission is happier and will last longer...

 

[steved]

... I now drop down to 5th when towing in any significant grade when towing, and the engine is right in it's sweet spot for power at 55 MPH with plenty of useful RPM to spare - and I'm sure my transmission is happier and will last longer...

I have a long trip coming up and even though I will lose a lot of ground speed, I'll probably drop to 5th just to be safe... I have read on several boards of the stripped splines from towing in 6th... maybe it was just the same person posting a bunch of different places? :-laf



steved

 

[Gary - K7GLD]

I have a long trip coming up and even though I will lose a lot of ground speed, I'll probably drop to 5th just to be safe... I have read on several boards of the stripped splines from towing in 6th... maybe it was just the same person posting a bunch of different places? :-laf



steved

That was a big plus with the tire upgrade to 285's - a little drop in RPM at the same road speeds - great when empty in 6th - and the effective ratio puts 5th gear RPM right where it's needed for towing in the hills. Grades are steeper here in our part of eastern Oregon, but narrow and winding - so can't keep road speed up like we could in the California Sierra anyway, so it was a good choice in our case.

 

[RJWEST]

Overdrive is for marketing, not for towing
If you run heavy:, straight through 1:1 is least strain on engine and trans...

 

[DDrees]

After some years now with the addetive in your transmission which one worked the best? Am's. Or Morp?

2001 Ram 6spd. w/coolers 78,000miles

White w/white mud flap's