Engine/Transmission (1994 - 1998) Broke it again

[dieselburner]

Well I snapped off the input shaft again on my transmission. This is the third time for the input shaft, broke the main shaft right behind third gear once before and stripped most of the teeth off of fifth gear once before also. I am considering installing zippers on the thing to get it apart easier this time. Seriously though, I am having a durability problem and I can tell you that I do not abuse the transmission by doing tractor pulls or street racing. It is occasionally used to pull a fifth wheel trailer but I haven't done that in about 3 months. I did get on it once about 3 days ago and I think thats what did it this time. I wasn't shifting, I just flipped the valet switch off and stood on it on a straight road and blew some smoke. That afternoon it was hard to shift and two days later the input snapped off. I am considering going to a more durable transmission or even (gasp) down sizing my power. Does anyone have any ideas as to what I can do to make this transmission last behind the engine?

 

[GrantP]

NV5600 swap?

 

[bighammer]

I wonder if you don't have an alignment issue with it. Maybe if it binds slightly the stress and wear is compounded, thus the early failures. Just a thought.

 

[JGheen]

That's what I would say as well. Those NV4500s are pretty stout and have heard of them being able to take up to at least 500+ HP. Of course, that transmission would be modified by Standard transmission to take that much. Thier aftermarket products to beef up the 4500 are very reliable for big power.

 

[dieselburner]

What type of aftermarket parts are available besides the 1 3/8 inch input shaft and the fifth gear nut upgrade? I am considering doing the bigger input shaft since I am on my third 1 1/4 inch shaft and that might stop the input breakage. But since I have already broken the main shaft and stripped off the teeth from fifth, I am not sure that this will take care of the problem. I can see how it might be an alignment issue if it was just the input shaft breaking but I am having the main shaft and 5th gear breakage as well. I never did have fifth gear back off, it just stripped the teeth. None of the breakages occurred from abuse other than ALOT of torque being applied steadily. I always apply the power pretty gradually so the breakage isn't from shock loading the gear train. I do have the fully spined main shaft in this transmission now. Has anyone went to an over the road truck transmission or do you know of a better transmission that can be used in our trucks?



edit-

How is the NV5600 compared to the 4500? Is it much stronger or are they having breakage problems as well with high power/torque applications?

 

[CumminsPower98]

The NV5600 is much stronger and I have not heard of them breaking. It wouldn't surprise me though with the power some of these guys are putting down.

 

[CATCRACKER]

my buddy broke his with 400hp. of course he pops the clutch with 18000# behind him and use all 400hp while towing. so i will say yeah they are the tuffest trannies around but you can tear them up. with a good clutch they dont allow fof much slippage lick a TC can. the massice tq of a turned up cummins can brake more stuff than one might think. go to a nv5600 for sure. that is an easy swap for you truck!