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Hard Shifting NV4500, less than 2 years on clutch

DieselAmateur

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I'm pulling the tranny this weekend to swap in a new one, but wanted to post here in case I'm missing anything before tearing into it and can't get parts after hours.

Last April I did a new clutch, pressure plate, throw out bearing, fork, fork pivot, and slave cylinder. Clutch was NAPA brand equivalent of stock/ OEM

Transmission was rebuilt by a local shop in 2017 using takeout parts. Was never happy with the gearing as my ratios were off, think early NV3500 gears were used as my RPM to speed has never matched up. But the shop gave me a huge break on the job so I couldn't really complain.

Sometime around this spring/ early summer the trans started grinding going into 4th. No big deal, figure just bad synchros. Decided that if I was going to go through the trouble again of pulling the trans I'd want to put in a new one or do a full rebuild as I don't want to replace one part only to have another go soon after and have to pull everything again.

Then a few months ago the transmission starts popping out of 2nd when throttle is applied. I have to literally pull/ hold the stick in 2nd to stay in gear. Not ideal and pretty nerve racking when pulling a 3.5 ton mini excavator. So current trans has got to go.

After pricing things out on just parts alone it was more cost effective for me to buy a new rebuild from High Gear Transmission. I splurged for the cryogenic internals because of the P400 and future power mods yet to go on the truck.

The truck/ trans ran fine otherwise and sat for the thanksgiving break. Driving it to start the week I have to force into every gear. Hard to get into 2nd, slightly easier to push into 3rd and have to quickly pull into 4th, otherwise it just grinds and won't go in. I could briefly get it into 5th, but that's now impossible. So since Monday truck is essentially not driveable.

The master cylinder is full, pedal travels and feels normal as far as I can tell. With the truck off I can shift into every gear without issue. Running she doesn't want to cooperate no matter how many times I pump the clutch pedal. Last topped off the fluid mid summer before a long drive, have always used the specific GL4 fluid for this transmission. Fresh fluid was put in last year when I did the clutch, and the trans temp gauge has always read normal, so I'm pretty sure fluid isn't the issue.

I'm posting because I'm confused as to whether this issue is solely internal to the trans and will go away once the new one goes in, or if it's external to the slave/ bearing/ clutch assembly. It seems to be behaving more like a clutch/ pressure plate issue, but I just did all that a little over a year and a half ago and wouldn't think it would go bad this fast.

I was also advised by the folks at High Gear to go with a stock clutch and was specifically told to not get a South Bend or any other aggressive setup. Better to have some slip and save the trans, in their words. Anyone think otherwise?

So is there anything I'm missing about what could be wrong, or does anyone know what the more likely problem is based on my symptoms? I'm probably going to buy another clutch assembly before the weekend just to be safe since I can always return it. And I'll be tearing into it come Saturday morning, but always prefer to be more prepared for what I'm getting into, so I'm trying to cover all my bases. Thoughts?
 

MrMarty51

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I might be wrong but to me it seems that the clutch is not fully releasing.
What it takes to fix that on a hydraulic actuated clutch unit I know knottt.
Others will most likely kick in with some good suggestions.
 

WarWagon

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A transmission alone will not solve this. Something is spinning the input shaft when the clutch should be released.

Sounds like the pilot bearing may have locked up.

You can youtube ways to test the hydro by removing and blocking the piston. They hydros may have air in them or otherwise failed and not releasing the clutch.
 

DieselAmateur

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@WarWagon I agree that its not just the transmission alone, appreciate the second opinion

Confused about the pilot bearing- if the pilot bearing locked up wouldn't that slow down the input shaft, something that is not happening? Or do you mean throw out bearing?

Hoping it's just a bad slave cylinder. Thing is when I hit the clutch and start the engine with trans in gear it seems everything is fully disengaged- truck doesn't try to move as the starter turns the engine. I'll be finding out soon enough, guess a new slave cylinder should be in order too.
 

schiker

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Check spin down by trying to shift into a non-synchronized gear. Reverse isn't synchronized on my 97. So from neutral press clutch and try to shift into reverse if it doesn't stop grinding and drop into gear quickly its probably has other issues too compounding your problems.

GL4 is not specific enough for the NV4500 if it has OEM synchro's it should be equivalent to Castrol Syntorq. There are a few synthetics that are ok but check into them. A transmission shop told me don't go long on your first change of fluid as initial wear on synchro's contaminates fluid. I have heard of recommendations to overfill it a little iirc a pint.

Could be lots of things. The pilot bearing on this setup seems weak IMO and tends to wear out which causes more input bearing stress. Then they will feed off each other so once any wear starts it snowballs. Next, the clutch and PP are not all that tough. Neither are any of the hydraulics. Again once wear starts it snowballs. Any extra heat from loose input shaft runout (from wearing pilot and input bearing) just increases stress on the clutch.

Specifically, on the pilot bearing, it needs to be installed at the proper depth for best performance. I'll try to find my post on it.

There is also a rear nut on the 5th gear that can come loose. A dampener was added to transmissions with solid flywheels so the pusle of power through the transmission is fairly harsh IMO and all that dynamic micro flexing is what is so hard on manual transmissions. I am not as up to date but don't think any other gasser application has problems like this with the NV4500. The N4500 just needs to be beefed up for types of diesel engines. IMO it is not as much the clutch friction material but the hub spring pack that is more of the problem on early solid flywheel models. Again this points to the harsher pulse of power of the diesel cycle. Maybe the friction material contributes if there is a lot of slippage or micro slippage that can compound a weird harmonic with the hub spring flex ??????

In summary its go big and replace everything in the bellhousing every time or it just won't last like the first time.
 

schiker

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If the pilot bearing is worn it lets the input shaft run out more. Point your finger at something and turn a little circle pointing with the tip of your finger this is what happens with a worn pilot bearing.
 

DieselAmateur

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Thanks for the info. I didn't know the pilot bearing had to be set a certain depth- would love to see your post about it before I get into it this weekend.

Pilot bearing was new in 2018 when the engine went in. Everything else in the bellhousing was new last April. When I pulled the trans last April I could still see the red grease on the bearing from when it was installed two years prior.

Fluid used was the genuine fluid specific for this trans, got directly from stealership.

This trans had the 5th gear fix, and the new one going in will also have it in addition to the cryo internals

thanks for the tip on seeing how it feels going into reverse. From what I can recall it seemed to go into reverse pretty easy relative to everything else.

Sounds like all signs here are pointing to clutch not fully disengaging, I appreciate everyone's input. Will gather all necessary parts for the job this weekend.
 

schiker

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Some of my pics are in this thread by Chris. It is also a good thread by Chris. I just wanted others to be aware of the pilot depth issue if they did not know. Some years may be different it is important to measure the stack-up of the parts.

Expand this quote and read what I added in red.

@WarWagon I agree that its not just the transmission alone, appreciate the second opinion

Confused about the pilot bearing- if the pilot bearing locked up wouldn't that slow down the input shaft, something that is not happening? Or do you mean throw out bearing?

If the pilot bearing locks up then the input shaft still spins with the crankshaft.
If the pilot bearing is completely worn out and the input bearing wears it allows the clutch to get a little more out of the concentricity of the crank to the transmission which can lead to out-of-balance / out-of-concentricity forces and everything just goes to crap. One time once my input bearing started to fail completely it took out the input seal and snowballed wear pretty quick.


Hoping it's just a bad slave cylinder. Thing is when I hit the clutch and start the engine with trans in gear it seems everything is fully disengaged- truck doesn't try to move as the starter turns the engine. I'll be finding out soon enough, guess a new slave cylinder should be in order too.
The disengaging it sounds like you are experiencing could mostly just be the slave or master at this point but I just wanted to point out it is a whole system.

When doing all the work of dropping a transmission at home I mean go big pilot to input bearing replace it all if it has appreciable miles on them.
 
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schiker

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I don't explain it very well in my pics on that thread. Look at the picture of my worn pilot bushing cut in half placed on the input shaft. From the wear pattern left you can see it leaves some area at the end of the tip of the input shaft not engaged into the bushing. This is unused wear surface that should have allowed the bushing to last longer.

Warwagon mentions a better pilot bearing for the dodge from south bend and it looks like I missed replying to it. They didn't offer a better input bearing for GM back when I did mine. I think the crank it too little to mod. There was some discussion a long while ago of trying a Kevlar pilot bushing but believe it fell out of favor.

I liked the look of the stepped pilot bushing I posted. It seemed it might be almost full-proof installation depth if the stack-up measures correctly and allows maximum wear surface contact or bearing wear distribution length or decreases the psi loading on bushing etc.
 
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Rockabillyrat

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I was always taught NOT to use bearing grease on pilot bushings. They are a oilite bushing and do no work well with bearing grease, and can cause issues if grease is used. You should use oil on a bushing style pilot and grease on a bearing style pilot.
 

schiker

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I agree Rockabillyrat. In my picture I have a needle bearing. It sorta looks like the bushing but that is just the end picture and it has a bushing and race/cup assembly iirc and the bushing part holds the little seal to keep clutch dust out of the needles and grease. The first needle bearing I took out was disintegrated and needles gualled to input snout - the cup of bearing was there but the seal and seal housing was all torn up and worn away. I couldn't tell the depth it was installed. The next repair I tried a bushing but think I installed it too deep. I read and talked around some and it was sorta 50/50 which was better the needle bearing or bushing. I went back with needle bearing installed to correct depth figured that was factory perfect :nailbiting: .

I have done both 1 dry bushing installed deep and 1 needle bearing with a little added grease installed to right depth. I don't know I thought the first needle-bearing I replaced with bushing might have been suspect as too deep as it was a repair also. I might change my mind and go back to bushing depending on what it looks like on my next disassembly.

One mechanic I talked to said he always put a dab o grease in a bushing. I said but won't the grease collect and hold clutch dust then form a lapping compound to increase wear and the mechanic said he had just always done it :rolleyes: .
 

schiker

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I have a question though for my next time at some future date and my knowledge base.

At the coupling of transmission to transfer case. Do ya'll grease the splines or oil it and let the transmission oil splash lube it? I think the overfill recommendation is to help lube this??????

I think I put it back with oil wiped on it the last time but the first time there was this semi-dry mess of gunk that was on the splines (deeper it was drier on the splines). I assumed was some semi-dried grease thickener that the oil and heat might have sorta washed out the lubricating properties and or damned lube from getting to deeper spline connection????

Or it could have been some Extreme Pressure additives of grease leftover I don't know.

What are you supposed to do there?
 

Grisley1958

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Your problem could be coming from a worn input shaft. You said it was rebuilt with used parts, and if the splines are worn the clutch plate does not slide well enough on the splines to release completely from the flywheel. Do you still have the two piece flywheel? When I replaced my Clutch in my 94 C3500 6.5, I went to the solid flywheel and was very happy with it.
 

Twisted Steel Performance

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I just went through this, new tranny from the same place, and they said the same thing about the clutch.. i went with the SB high hp kit anyway. The true fault is the t/o bearing, it'd not the correct length, there are 6 or 7 different lengths ... i used a novak adjustable t/o bearing and a brass pilot. I have a thread here with links and pics I'll look for later this afternoon.
 

jrsavoie

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I just went through this, new tranny from the same place, and they said the same thing about the clutch.. i went with the SB high hp kit anyway. The true fault is the t/o bearing, it'd not the correct length, there are 6 or 7 different lengths ... i used a novak adjustable t/o bearing and a brass pilot. I have a thread here with links and pics I'll look for later this afternoon.
I must have got lucky with the throw out bearing when I did mine. I j6st bought one and used it. I think it was an AC Delco. There's probably a post about it.
 

DieselAmateur

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Thanks for the help everyone

The pilot bearing is a needle type bearing like this one


I've heard of the bushing being potentially better, but have never seen one available for sale. @ak diesel driver and @Rockabillyrat, any chance you have a link?

I've never had to remove a pilot bearing, have only read about the bread/ grease method. Pretty straightforward?

@Twisted Steel Performance I remember your adjustable throw out bearing thread, @schiker linked to it above. Wish I had thought of that earlier in the week, would have ordered one for the job this weekend. I'm taking up space in a friend's shop so I don't know if I'll be able to get the proper bearing in time.

I hope it is a worn input shaft and the clutch may not be traveling/ releasing. This is my love/ hate relationship with the external slave cylinder; can replace the slave without having to pull the tranny like the concentric type, but several more moving parts means more that can go wrong.
 

Twisted Steel Performance

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The brass type bushing is the same as a s/b chevy, and I think @schiker posted a link to one in my old thread, any parts store should have one...

I don't remember if your year is internal or external slave, part of my trouble was my bellhousing was cracked more than half way around and when the clutch was pushed the bell would flex, check yours for cracks well...
 
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