smkn97s

I got a good deal, well I think its a good deal I bought a 96 12valve motor with around 250,000 miles its complete less the turbo but it has a spun rod bearing and a 2004 6 speed that has around 150,000 miles but the guy said he thinks it needs SYNCHRONIZERS it would go in gear if you didnt try to shift it fast he said you just have to shift slow. I paid 800$ for both of them Ive been through a few nv4500s broken mainshaft, inputshaft, 5th gear problems. So my ? is can the 6 speed take the abuse of power shifting and just running it hard ? I dont want to do this conversion if it isnt much stronger?

Josh.

Haulin_in_Dixie

Power shifting behind a Cummins, interesting. Are we talking a full throttle power shift?

Big Blue24

I was told by my tranny rebuilder that the NV 4500 was more stout than the NV 5600. I think that you are making a mistake if you are switching out for more strength. Plus, parts are hard and expensive to come by for the 5600. Now if you want lower highway R's, i think that the 5600 is a good swap. What on earth do you pull that requires power shifting?

smkn97s

I meant as in drag racing you know you have to shift fast . Because ive broke an input shaft and a mainshaft

Captain

in my experance DONT DO IT! someone else can tell you my storys but I thought swapping in a 5600 in place of my 4500 would be a good idea for a stronger trans too. Lets just say I havnt really been able to drive the truck since the begining of dec, its cost me over 10000$ and it has to be rebuilt again. Each rebuild lasts about 10 miles. I havnt even been able to abuse it yet. The motor runs like it has 100hp.

Haulin_in_Dixie

If you are towing, the 5600 is much better and smoother to drive. Racing, neither one is really built for it. The first gear ratio and the overdrive ratio on both are roughly the same. The 5600 just has another gear for a smoother pattern instead of the big jump in ratio of the five speed.

Captain

besides my bad experance. How do the 5 and 6 speeds compair as far as strength and speed of shifting and handeling of overall high power street abuse.

smokin06

i have one thing to say about the nv5600 JUNK that is the worst transmission made, i put one in my 97 and granted its making about 680hp but in 100,000 miles its been rebuilt 4 times, junk.

RonA

I swapped a 5600 into my first gen 3 or 4 years ago. Tranny had 25k on it when I swapped. I'm at 65k now. I had problems for a while with shifting into gear at a light. I installed a ball bearing pilot in it when I did my FE clutch. It now shifts like a dream. It is an outstanding tranny to tow with as far as gearing goes. I don't tow very heavy, but I am extremely happy with it. For drag racing, I wouldn't even consider it.

Captain

ball bearing pilot? where from? Sounds like I made a huge mistake. I'm kind of stuck with it though. Ill just let it rot in the shed if a5 speed can handle 1200+ foot pounds

RonA

I believe the number is a 1635RS. I think it is also labeled 1635-2RS. I believe it is a common bearing with diminsions of 3/4" x 1 3/4" x 1/2".The instructions I got from SB clutch were to bore 1.0 through to clear the inner race, c/bore 1/2" deep with a -.001 press fit. Make sure the bearing isn't so tight it is binding the inner race. The bearing was $15 at the auto parts store. This mod made a world of difference in the shifting of my 6 speed. I did the mod last summer and i haven't had to fight getting it into gear at a light since. Shifts clean and easy, hot or cold.

PourinDiesel

I wouldnt call the Nv5600 junk. I have seen many go over 100k miles without any issues with heavy towing to boot!

I have over 30 hooks to the sled with my NV5600 and so far its held up...

I know a guy in Ohio that runs super street and has over 150+hooks on a stock NV5600 (Yes thats right over 150 hooks to the sled without a rebuild). The weak point of the 5600 seems to be the mainshaft snapping when an extreme shock load is applied.
Far from what I would call JUNK!

NMCTD

The bearing is part #1635DC, you can get it at napa for about $20 or from a bearing supply house for about $10, then have your flywheel machined to fit it, it should look like this

Big Blue24

Well, my first NV 4500 went 214K and the first 176K of its life, it towed a 15K lb trailer every mile. It blew up coming down that big grade into Moab, UT when I was towing 8K. I then drove it 70 more miles to Monticello, UT before I decided to not push it any further. Talk about metal pieces, gear chunks, missing teeth, etc. It apparently quit lubing and the bearings blew up and then the flying metal smoked all of the planetary type gear connections. Bottom line, one tough tranny!

Valv

I have here a '01 with 256,000 miles and original NV5600, truck was a towing truck for all it's life and has no problem whatsoever with tranny.
I have a NV4500 on my .96 and seriously consider swapping for it, but I might be better off selling truck, I really like the shift pattern if you tow.