NV4500 growl/rumble. how worried would you be?

[GM Guy]

Hey all,

I am wanting to get everyone's opinion on the condition of the transmission before I head out and get myself possibly stranded.

The truck in question is my 1995 GMC C2500HD, it is the current Gooseneck truck, and I need to make a run to Nevada with some fertilizer equipment.

the transmission is gray in color, rather crappy re-paint, so its obviously been out before, so IDK what its got for guts or a clutch.

I have a magnetic fill plug in it, and allways have the fluid to the top, so if there are any filings, they should be getting caught. whenever I check there is little to no residue on the magnetic plug. depends on how much I scratch 3rd with the wore out synchro.

the part that concerns me is that it has a low growl/ rumble in neutral while idling, and will rattle/groan when you let off the throttle putting around in lower gears, makes more noise the less load is on it. the more the load, the less the death rattle. under load in all gears it has little to no noise, and will make none whatsoever in fifth, accel, decel, constant load, etc.

so I ask you folks, do you think the tranny is ok? the lack of shiny material on the magnet and the fact it is dead quiet in fifth makes me think it is ok, but the lower gear noises have me concerned. this truck should have been SMF from the factory, correct? if it was DMF, do you think they could have put a solid in without changing the clutch and that is where the noise is coming from?

any input appreciated, thanks!

 

[bison]

Hard to tell what is causing that without opening the tranny up.The fact that fifth gear as you say seems the quiest makes me think the needle bearing in the end of the input shaft where it supports the mainshaft has an issue. in fifth gear both input and mainshaft run nearly the same speed and the needle bearing hardly moves.

I have a neighbor who had that bearing seize solid with the truck idling,..neighbor was in the house when all of a sudden he heard some commotion and looked outside only to see the truck trying to climb the porch steps before the engine stalled :hihi:

Could also be 5th gear nut backed off a bit??

 

[Burning oil]

I can't remember what its called but GM makes an additive to quite noisy gears in manual trans.

 

[WarWagon]

GM stuff gives you a warning before you walk most times. Sounds like this is one of those times. Pick another truck until you get this one fixed. Towing will kill your 'profit' on a run.

 

[GM Guy]

Should I pack a spare transmission with me? only 200 lbs of dead weight, it will be like having 4wd! If i leave the shift lever and bellhousing behind, it should be compact.

 

[NVW]

One other thing that can transmit noise to the tranny is a bad HB. I had a grain truck that broke the crank, when new crank and HB were installed the tranny noise was gone. It was more of a rumble sound.

 

[GM Guy]

good point leo,

the SM465 in the 91 half ton quieted down some when i put the fluidampr on. the one on this one didnt look bad, but I will look it over a little closer.
I did notice the extra NV4500 out of a 1995 half ton with a 350 gas had a damper on the rear yoke, but the one in the truck doesnt, but neither does a NV4500 on e-bay from a 1995 diesel, and IIRC the 1996 C2500HD doesnt have one either. surely an extra damper cant hurt?


do you think changing oil will prolong it any, or would changing it just be a waste of money?

IMO, if the needle bearing is going, shouldnt i be getting metal chunks on the magnet? thats not to say I dont have other non ferrous metal chunks floating around, but the oil doesnt look too bad.

 

[SmithvilleD]

Believe my '95 came with a dual-mass, but had been switched to single-mass flywheel with the matching sprung clutch hub. But I don't believe mine has the damper on the output shaft that GM used when they stopped using dual-mass flywheels. Think I've got a pic of this part at home if you're interested.

Anyway, mine makes no noise idling out of gear, or in any of the gears under load. But in 1st with no load, once the gear lube is warmed up/lower viscosity, the tranny basically rattles (believe this is from the abrupt diesel combustion pulse & any additional harmonics) a bit while loafing along. It you touch the brake enough to load it just a bit, the noise goes away.

I intend to add that output shaft dampener, but haven't gotten it done yet. Dennis and others have said adding the dampener makes a noted improvement in NV4500 manners on the trucks that were originally DM but swapped over to SM flywheels.

Thinking I've seen a 2WD Cummins/NV4500 combo that had the external dampener/yolk combo? Not certain, but might be worth checking if there was such a Cummins/NV4500 yolk/dampener combo, & if it's compatible with the GM NV4500 version.

 

[GM Guy]

I think on the 2wd GM's, minus the 3500HD, I am 95 percent sure that the internal damper cannot be used. the gas NV4500 I have has the yoke damper, but none of the diesel ones do. I will go double check the 96 tomorrow if it is still light out when I get back from the day trip up to get a combine header and make sure it isnt either.

do you think that 95 was the transition year between SMF and DMF?

 

[SmithvilleD]

View attachment Manual Transmission Rattle Noise At Idle.doc

Here's a GM document that I think covers: internal damper is for 4x4 trans btwn trans & transfer case, yolk dampener is for 2WD NV4500.

You can read the whole document, but here's the relevant part regarding where the new dampener goes when replacing a DM with SM flywheel.

4-WHEEL DRIVE: THE DAMPER IS INSTALLED BETWEEN THE TRANSMISSION AND THE TRANSFER CASE. TO INSTALL THE DAMPER, THE TRANSMISSION REAR EXTENSION HOUSING MUST BE REMOVED. REFER TO THE APPROPRIATE YEAR UNIT REPAIR MANUAL, SECTION 7B8, NV4500 MANUAL TRANSMISSION FOR DETAILS. WHEN INSTALLING THE DAMPER NUT, APPLY LOCTITE(R) 242, P/N 12345493, TO THE NUT THREADS AND TORQUE THE NUT TO 325 LB. FT. (441 N.M).
2-WHEEL DRIVE: THE DAMPER IS PART OF THE YOKE ASSEMBLY. REPLACEMENT OF THE YOKE IS REQUIRED. TO INSTALL THE YOKE, REFER TO THE APPROPRIATE YEAR UNIT REPAIR MANUAL, SECTION 7B8, NV4500 MANUAL TRANSMISSION. WHEN INSTALLING THE YOKE/DAMPER NUT, USE LOCTITE(R) 242, P/N 12345493, ON THE NUT THREADS AND TORQUE THE NUT TO 325 LB. FT. (441 N.M).
IMPORTANT: YOKE/DAMPER NOT USED ON 15,000 LB. MODELS

 

[SmithvilleD]

Here are some pics I collected a while back. The yolk/dampener is obvious. Believe the others are just different views of the 4x4 dampener by itself, shown on the shaft, then inside the housing, etc.

 

[GM Guy]

updates:

checked the 96 trans on the 96 ECLB 6.5L 5spd 2wd in sig, and it had the damper. the extra 95 NV4500 had the damper, unit in truck doesnt.

also, 3384 miles piled on in one round trip, KS to NE to pickup the fertilizer equipment, then straight shot to western Nevada, back to the Idaho farm, then back to KS. did not change the trans, the current one growled and rumbled me to nevada and back.

the handshaker prayer was pondered on in my mind a few times. : Yea, though I drive through the valley of the shadow of slushbox, I will fear no transmission failure: for thou manual transmission art with me; thy constant mesh gears and thy gear oil they comfort me.

I may make anouther run, but would REALLY like to change this one before then.

 

[83GMCK2500]

GM Guy, don't want to hijack your thread or derail it, but if you come across anyone parting an NV4500, I NEED one of those dampers. Thanks in advance.

 

[Burning oil]

Also, not to hijack. I got an email from my supplier last week. They have brand new aftermarket NV4500's for $2500 + shipping.