rebal

I hope so too I really did like the first 150k it was the last 5000 miles that I wanted to burn the truck .I really trusted standard transmission to find the problem. we will see if the g56 fairs as well as the first 150k

SIXSLUG

That's what they said, they were afraid it would shoot out like a missile if they tried more force. He also said the others he has rebuilt pressed off pretty easily. Figured the high heat galled it together.

My rebuild has about 80K on it, shifter tends to wiggle left to right in second, original didn't do this....

jefe4x4

165K miles on mine. Bought it new in 2001. Changed the oil to Red Line @ 100K. It has been flawless. New clutch @ 165K. Actually, I cringe when I read these horror stories. In 2003 i met a mechanic who took the NV5600 repair course and he said it had some funny things to do that you would overlook if you were used to working on NV4500's.
When I researched the NV5600 i found it has a maximum weight rating, some combination of tow/haul that stopped at 26K pounds. ANY stress above that poundage would grenade the trans. I have been at the GCWR of 22K pounds a couple times.
My take on the trans is that it has very little deflection as the case is cast iron. No intermediate bearing needed. But it's a heavy sucker @ 360 pounds. I have a feeling that the heaviness is what killed it after so few years of production.
I have a friend who bought a cheap, used '04/NV5600 truck but he complained that the synchos were bad. I said, it has the wrong oil. He had the oil changed to the factory recommended oil and Voila! the trannie was back in business. I'm thinking the wrong oil is a common mistake.
Some time ago, when I was collecting medium truck transmissions, I found a possible replacement for the NV5600: a Clark 280VO, 5 speed w/ O.D., 5 ton, all synchro truck trans from a 1979 Ford F-700 4X4 Dump Truck. This is the rare O.D. model. Most of the other 200 variations on the Clark 5 speed are 1:1 in 5th. Only 295 pounds. Still has the divorced T.Case lever attached. Kind of a lightweight but with unbreakable grunt. ratios: 5.98/3.50/1.86/1.00/0.80/5.04R. 10 spline, 7" stickout, Ford gas engine b.h. pattern.



The tape is on there when I steam cleaned it. It's still sitting around in my garage holding the compressor from walking out the door. Yep, boat anchor.
jefe

rebal

Well the wife and I just returned home from our trip .we headed south for a month there about .transmission worked great . We pulled some real steep grades on hwys 269 I5 and I8 .on 269 I pulled 38 psi boost for 20 minutes up one grade and the trans never even got to 150 at first I thought I forgot to hook up the temp gauge so I ran it in 6th for 1hr before it even came off the 140* Mark and in 5th it never got past 140*.I filled it with Delvac 50 so on cold mornings it was stiff but after a few miles that was over. Also the G56 I got is an early model and has the lower 6th ratio and for my use its perfect with my setup .the 5600 was a tad tall in 6th and .I was pulling 12500 this trip normally closer to 17k (towing in 5th) and averaged 9mpg with a strong head wind a 13mpg on the flat. Overall I'm happy with the swap and it shifts way nicer too. I definitely think the 5600 is tweeked internally causing the constant breakage. I will junk it because I really don't want it to end up being a problem for someone else. If anyone ever needs info on what's needed to swap pm me.

rebal

well thought I would just give an up date, it's been a while. The g56 has be working flawless after several thousands miles .realy like my truck again. Imho it is a lot more refined 6spd happy with the swap

Dieselbuilder

You now no too transmissions are the same you could have a bad box i have seen this on larger trans some just wont hold together