NV 5600 sticky shifting

[BERT E SHETLER]

Hello.
I have a 04.5 2500 4x4 with the NV 5600 6 speed manual that I use to pull our 32 foot fifth wheel. I've only pulled the trailer 3 or 4 times yet, but from the beginning, it seemed like as soon as it got hot, the transmission was almost impossible to shift. It shifts excellent all the time when I'm not towing, only has trouble when pulling heavy.
After reading up on it, I changed out the trans oil and used Royal Purple synchromax oil. Still sticky. After reading some more, I dumped in an extra quart through the top of the trans, and this made it a little better, but still sticky. After that, I found some knockoff pod-type trans coolers from ebay. I was impressed when I got them at what good quality they seemed to be, so I installed them and filled it up, once again removing the shift tower and adding an extra quart. All tolled, I think it now has 8 quarts in there.
Took it out for a hundred mile spin pulling the trailer on a cool day the other day, and it's definitely WAY better, but still fairly sticky feeling when it's been pulling hard, up hills and such.
One of the pod coolers has threaded holes with plugs in them, so I was considering plumbing in a oil cooler with a little pump to circulate the oil.
If anybody has any advice about this transmission, I'd like to hear it.

Cheers
Bert

 

[GCroyle]

Bert

Mileage on truck, clutch original or replaced or replaced mileage and description of clutch if replaced.

Engine running, clutch pedal on floor select 1st gear. Slowly bring clutch pedal up and measure how far pedal comes up before clutch makes truck start to move. Initial engagement.

Engine off. Two fingers jab the clutch pedal down. How far does the pedal move with just the two finger poke.

Gary

 

[BERT E SHETLER]

Mileage is 176000.
No idea on the clutch. Bought the truck with 165000 only a couple years ago.
I did talk to one of the previous owners who said he bought it at auction with a broken transmission, and he rebuilt it. (He said he owned a transmission shop.) but he didn't say whether he replaced the clutch. He DID say it had pretty low mileage when he bought it, and that he drove it over one hundred thou, so IF he replaced the clutch, I would guess it's got a hundred thousand on it.
The clutch works perfectly. No chatter, engages smoothly.
With your "two finger jab" it goes down right at 1.5 inches.
With the truck running and in gear, its a little hard to measure, but I'll guess it comes up about 3 inches before the truck starts to move.

 

[GCroyle]

Bert,

Outside of lube experimentation you've already done the only external clutch system that you can explore is the clutch release system. And this actually requires some real honest measuring with the testing.

1. These systems DO NOT have freeplay, period.
2. I just did the two finger jab on my 2005 NV5600. More like 3/4". Didn't fire it up to do the reserve travel measurement but it's likely about 3"
3. To measure the reserve travel the upward pedal movement before initial engagement take a good tape measure and extend it thru the steering wheel and hook it behind the clutch pedal. Distance to steering wheel, record it. Now repeat the test and allow the tape to retract noting the distance traveled against the steering wheel. Report back.

If you still have questionable two finger jab distance this test can be refined to greatly improve accuracy. Remember alternative is pulling or paying for trans R&R. Remove clutch slave cylinder, no one touches clutch pedal yet. Remove push rod and dust cap. Inspect behind dust boot look for fluid. Have you checked the fluid level in the reservoir? Adding fluid is not a fix but low fluid is an indicator. Attach a steering wheel puller with bolts across the face of the slave cyl, turn screw in until it contacts the piston. Now turn it in additional 1/2" or so. Secure the cyl do not let it hang.

With the cyl piston blocked with STEEL repeat the jab test. But this time remove the clutch start switch and mark the position of the push rod against the master cyl body. A pencil or fine Sharpie works well. Now jab and hold. Mark push rod position again. Repeat this test so you're comfortable with markings. Now what is the distance between the marks?

A fully bled NV5600 stock hyd system the push rod travel jabbed with slave cyl blocked you're under 1/8"-1/16". Anything more is first suspect an air bubble. At the same time this is setup repeat the jab but look way up on the pedal at the top anchor point and look for slop in the pedal to pin connection. These systems don't bleed out but they can be burped of air, that's a different post.

Sounds like unnecessary work or expense, ain't nothing compared to trans repair best to rule this out. If you're not a DIY let us know that too.

Gary

 

[AH64ID]

I used Amsoil in my NV5600 and it was one of the smoothest shifting NV5600’s I ever drove, hot or cold. It had a couple issues every now and then, but that’s par for the course with that trans. It did shift nice enough that even my diesel mechanic said he hadn’t driven one nicer.

I can’t comment on the fluid or the trans causing the smooth shifting, as I never experimented with other fluids… but I do know it was a combo that worked well for me.

 

[bcbender]

Some are just that way... Mine was always finicky when shifting, even after new clutch and trans overhaul, I got used to how she wanted to be driven... my friend's 05 shifts like a car.. night and day difference,..same trans, same clutch, same Amsoil MTF...

 

[BERT E SHETLER]

Some are just that way... Mine was always finicky when shifting, even after new clutch and trans overhaul, I got used to how she wanted to be driven... my friend's 05 shifts like a car.. night and day difference,..same trans, same clutch, same Amsoil MTF...

Does yours get worse when it's hot?
This one is super smooth when cool, even when hot, as long as it's running light. But when it's pulling heavy it starts acting up.

 

[bcbender]

No not really, but I did mostly towing with my trucks so who knows, it was never "super smooth"... I put a temp gauge in my Fast Cooler and it would get hot pulling the 5er in 6th but direct was much lower.

 

[Ozymandias]

If you are going the route with an external cooler/radiator.
Check for differential cooler kits in the www, so get everything you need in one package for a decent price instead if cluttering parts together.

 

[Wiredawg]

My former 02 3500 with 5600 used to do what you describe when trans fluid was hitting 25K miles. Mine only liked the factory fill, it was funny the discussions we had back then about it. Quaker State/Pensoil (factory fill) worked great for 25K miles, pulled 18KLb 5er with it. I experimented with Redline and Royal Purple with no joy.

Good luck figuring it out.