The NV4500 from hell, a call for help.

[ForcedToPutThs]

Around a year ago I bought a 1986 Chevy m1008, an ex-military squarebody that the previous owner swapped a 6.0 LS and a 5 speed NV4500 into. It's made a grinding noise in 4th and 5th, and a bad vibration in 5th since purchase. I'm currently at a standstill after tearing into the transmission and transfercase multiple times and finding nothing wrong with it. At this point I may have no choice but to run it until it eventually grenades itself and leaves me on the side of the road one day, but I'd like some more input before I say screw it and run it as is. I've included videos both going down the road and sitting still in the shop with no transfercase or driveshafts.

Spoiler: Videos of noise

Here's what I know about it

• It is definitely caused by something inside the transmission, I have run it sitting still in the garage with nothing but the engine connected to the transmission and it still makes noise.
• The vibration and some of the noise seems to be caused by load, running it without a load on it (nothing connected) cuts down on the noise and reduces the vibration almost entirely.
• The problem seems to get worse with gear speed, it happens all the time in 5th but only gets bad in 4th once I bring the rpms up a bit and get it spinning faster.
• 4th and 5th are the problem gears, I haven't gotten it to make noise in 3rd or any other gears.
• While driving down the road one day in 5th the vibration and most of the noise stopped. After down and upshifting a few times it came back, I haven't been able to replicate it again (thought I haven't put many miles on it since).

Here's what I've tried so far

• Tore the transfercase all the way apart, found nothing wrong.
• Took the transmission apart down to the mainshafts. The only thing I didn't take off were a few gears (1st 2nd and 3rd) off the mainshafts themselves because they looked like they'd be a pain without proper tools and aren't my problem gears. Found nothing wrong.
• First time I had it apart I looked it over, reshimmed the mainshaft/countershaft endplay, and put it back together with no change in the issues.
• Second time I took it apart I looked it over again and put this bearing kit in it, put it back together and still no change.

I'm completely lost at this point, I have a transmission that I can't find anything wrong with yet obviously has something very wrong with it. If anyone has any ideas please let me know, otherwise I'll have to just run it till it blows or throw another one in there because I'm out of things to try. Thanks.

 

[PAE]

What type of oil are you running in it ?

What year is it ?

Did the noise start soon after the oil was changed ?

 

[Scooter]

Help tag is not for your blown tranny. Unless you are stuck on the side of the road inop with said blown tranny.

 

[ForcedToPutThs]

What type of oil are you running in it ?

What year is it ?

Did the noise start soon after the oil was changed ?

Previous owner said it was out of a 98'. The only thing on it that looks to be different is the front bearing retainer which is off of a 92'-95' because he ran the earlier model style external slave cylinder.

Running 5 quarts of Red Line MT-85 Full Synthetic. Factory spec is around 4 quarts but most people online say they run 5 because it helps with noise. Replaced the oil when I rebuilt the trans, no change.

 

[total newb]

4th is straight through power. No other gears should be under load.


Now the wierd thing is you said 98 trans with early input retainer.......... does not compute
98 trans is big retainer, large bolt pattern and late style belhousingn as well as different 1rst ratio

Early bell housing is the only way youre getting the early clutch system to work but it doesnt bolt up to98 case nor properly locate the input retainer.

We need some pics. Bellhousing, bolt to trans, and with any luck you have some pics of the input with the bell on out of the truck.

 

[total newb]

You also didnt put it together but i hope at some point you checked the input pilot bushing/bearing.

 

[PAE]

The redline oil is compatible with the factory syncros ?

Redline speaks to that question.

MT-85 75W85 GL-4 Gear Oil

Popular replacement for NV4500, Hyundai, Kia, Nissan (Altima, Maxima, Sentra, Versa, 350Z and 370Z) and Mitsubishi Diaqueen fluid (for Eclipse, Lancer, and Evolution models)

www.redlineoil.com

Assuming you used the same syncros as factory ?

Ive never heard of it making noise just smoking the syncros when the GM or Dodge special oil isn't used.

Set the backlash to factory spec ?

 

[PAE]

Run it with drivelines disconnected ?

To see if you hear the same noises IE does it happen only under load of weight of truck ?

 

[Gravy]

No help, but if you have to tear it apart, try running it in 5th with no driveshafts connected.

Then remove the transfercase and run it again. (Not sure if possible)

 

[ForcedToPutThs]

4th is straight through power. No other gears should be under load.


Now the wierd thing is you said 98 trans with early input retainer.......... does not compute
98 trans is big retainer, large bolt pattern and late style belhousingn as well as different 1rst ratio

Early bell housing is the only way youre getting the early clutch system to work but it doesnt bolt up to98 case nor properly locate the input retainer.

We need some pics. Bellhousing, bolt to trans, and with any luck you have some pics of the input with the bell on out of the truck.

It's entirely possible it's just an earlier model trans. I never questioned it because it seemed easy enough to swap at first glance but looking at it now it seems more likely he got the year wrong. It has the square top cover which torque king says was run from 95' onwards. They changed the slave cylinder in 96' so chances are it's actually just a 95' model year.

I checked the input bearing, seemed fine.

The redline oil is compatible with the factory syncros ?

Redline speaks to that question.

MT-85 75W85 GL-4 Gear Oil

Popular replacement for NV4500, Hyundai, Kia, Nissan (Altima, Maxima, Sentra, Versa, 350Z and 370Z) and Mitsubishi Diaqueen fluid (for Eclipse, Lancer, and Evolution models)

www.redlineoil.com

Assuming you used the same syncros as factory ?

Ive never heard of it making noise just smoking the syncros when the GM or Dodge special oil isn't used.

Set the backlash to factory spec ?

I used the oil you linked, stock carbon fiber synchros still in it.
Unless you're talking about endplay (which I did shim into spec) I haven't seen any adjustment or spec for backlash for the nv4500.

I've already tried running it no transfercase and no driveshafts, they're the videos I have linked in the main posted titled "no load".

 

[total newb]

Im not talking about the input bearing, which you would see under the retainer when you disassembled it. Im talking about the pilot bushing/bearing in the back of the crank shaft.

95 is a bastard between early and late, early input and bell, early bell bolt pattern, and yes, late style sqr bolt on shifter and 1rst gear ratio.

 

[Oddball]

My first guess was end play. What did you set it to? My final guess would be pilot bearing.

 

[arse_sidewards]

4th is straight through power. No other gears should be under load.

Therefore alignment issue IMO.

Betcha he's got a roached pilot bearing or some shit

My first guess was end play. What did you set it to? My final guess would be pilot bearing.

He's a 25yr dealer mechanic so he set it to the same 3/8" he would for a warranty job.

 

[ForcedToPutThs]

Im not talking about the input bearing, which you would see under the retainer when you disassembled it. Im talking about the pilot bushing/bearing in the back of the crank shaft.

95 is a bastard between early and late, early input and bell, early bell bolt pattern, and yes, late style sqr bolt on shifter and 1rst gear ratio.

Sorry, typo, meant to say pilot bearing. I looked it over before I put the trans back in and it looked and felt fine. Didn't look old so I'd assume it got replaced with the engine swap.

My first guess was end play. What did you set it to? My final guess would be pilot bearing.

I've got the mainshaft endplay right at .002, right at the bottom of the .002 - .006 spec. I set countershaft endplay at .003 because that's the closest I could get with my shims.

 

[arse_sidewards]

Shit should be glass smooth in 4th even if most of the rest of the trans has fucked shit going on.

Bell-housing alignment? You sure the transfer case isn't the source of the grinding? What happens if you drive it in 1st/2nd and match engine revs to the vehicle speed so that things are mostly unloaded?

 

[bad zuki]

You also didnt put it together but i hope at some point you checked the input pilot bushing/bearing.

I’d check if the bell-housing centerline is centered on the crank centerline. It sounds like the one that failed on me going down the interstate. I had a roller pilot bearing fail and turn the transmission into 4th and 5 neutrals.

 

[blakes]

Definitely 100% use the GM PN 1234-6190 oil and NOTHING else. I know for a 100% fact the Amsoil stuff that is rated for an NV4500 will cause one to rattle excessively. I dunno about the Redline stuff though. I posted this on the old site probably 15 years ago or so and I think it holds true today.

Once you put the correct oil in there, repeat the test.

NV4500's rattle bad. Period. Although judging from your videos, I would also suggest taking another look at the pilot bearing.

 

[The Freeak]

Previous owner said it was out of a 98'. The only thing on it that looks to be different is the front bearing retainer which is off of a 92'-95' because he ran the earlier model style external slave cylinder.

Running 5 quarts of Red Line MT-85 Full Synthetic. Factory spec is around 4 quarts but most people online say they run 5 because it helps with noise. Replaced the oil when I rebuilt the trans, no change.

EDIT- this may be irrelevant now that I read more of the responses...

Did you match the input bearing with the input bearing retainer? I think I just saw something about this on the NV4500 FB group- guy had mismatched parts.

 

[Winchested]

Mine rattles '94 external slave. With the later top cover. Removed the damper on the main shaft.

Fully rebuilt all end play in spec.

I think a big issue is the only main shafts available for the GM versions is a shity one made in China.

But judging by the original main shaft I took out that had half the splines worn away (32 spline output) they're just a rattle trap trans to begin with.

The gear splits fucking suck for a a gas engine. I hate mine to be honest. I'd love my IH T19 back.

 

[PAE]

You didnt replace the syncros ?
If not why not ?

I agree with the earlier poster use GM OIL.

Dont cheap out on items where using used items or potentially inferior items can cause problems.


And yes use a new pilot bushing (bronze) every time the crankshaft hole is exposed unless it wasnt run or damaged during R&R.

It's entirely possible it's just an earlier model trans. I never questioned it because it seemed easy enough to swap at first glance but looking at it now it seems more likely he got the year wrong. It has the square top cover which torque king says was run from 95' onwards. They changed the slave cylinder in 96' so chances are it's actually just a 95' model year.

I checked the input bearing, seemed fine.


I used the oil you linked, stock carbon fiber synchros still in it.
Unless you're talking about endplay (which I did shim into spec) I haven't seen any adjustment or spec for backlash for the nv4500.

I've already tried running it no transfercase and no driveshafts, they're the videos I have linked in the main posted titled "no load".

 

[Oddball]

Sorry, typo, meant to say pilot bearing. I looked it over before I put the trans back in and it looked and felt fine. Didn't look old so I'd assume it got replaced with the engine swap.


I've got the mainshaft endplay right at .002, right at the bottom of the .002 - .006 spec. I set countershaft endplay at .003 because that's the closest I could get with my shims.

I thought I remembered reading somewhere that the end play was updated by the manufacturer to be even tighter, like 1-2. I read other people set them up right at zero. Why you want any end play baffles me.

 

[PAE]

Thermal expansion.

I thought I remembered reading somewhere that the end play was updated by the manufacturer to be even tighter, like 1-2. I read other people set them up right at zero. Why you want any end play baffles me.

 

[ForcedToPutThs]

Shit should be glass smooth in 4th even if most of the rest of the trans has fucked shit going on.

Bell-housing alignment? You sure the transfer case isn't the source of the grinding? What happens if you drive it in 1st/2nd and match engine revs to the vehicle speed so that things are mostly unloaded?

I've been testing it without the t-case. I haven't tested transfercase with no driveshafts yet, but compared to driving down the road it's a little quiter and most of the vibration goes away. I would assume this just has to do with it not having a load on it. I've already taken the t-case apart and found nothing wrong with it.

I've yet to get it to make any noise in 1st 2nd or 3rd. 3rd not making noise confuses me. I could buy that 1st and 2nd just aren't spinning as fast as 4th and 5th but I've had it up to 4000rpm in third and still heard nothing.

I’d check if the bell-housing centerline is centered on the crank centerline. It sounds like the one that failed on me going down the interstate. I had a roller pilot bearing fail and turn the transmission into 4th and 5 neutrals.

Did it make any noise/vibration prior to this or just quit one day? Did you only lose 4th and 5th? All others were fine?

Did you match the input bearing with the input bearing retainer? I think I just saw something about this on the NV4500 FB group- guy had mismatched parts.

That would probably be my post lmao, I got it solved before I put the trans back together. All fits good now.

Definitely 100% use the GM PN 1234-6190 oil and NOTHING else. I know for a 100% fact the Amsoil stuff that is rated for an NV4500 will cause one to rattle excessively. I dunno about the Redline stuff though. I posted this on the old site probably 15 years ago or so and I think it holds true today.

They no longer make the Castrol Syntorq that was originally specified for these transmissions. Redline is supposed to be the closest to factory spec you can buy today.

You didnt replace the syncros ?
If not why not ?

It shifts fine and they passed a visual inspection.

 

[bad zuki]

Did it make any noise/vibration prior to this or just quit one day? Did you only lose 4th and 5th? All others were fine?

It was Fine until it wasn't. Input shaft went sideways in the pilot and completely destroyed the input shaft and counter shaft. I only had 4th (direct drive). So I put it in low-4th, then ripped it to hi-4th and drove off the interstate.

I've been doing alot of research on the nv4500/ls and alot of the aftermarket bellhousings aren't perfectly in line and cause issues. Also check your clutch. Might have lost a weight.

 

[PAE]

Quicktime is the only known bellhousing that works with the early up to 1995 smalish bearing retainer to chevy engine bolt pattern I'm aware of.

Its a spendy proposition but in this instance you get what you pay for.

Assuming your transmission is an early and not a late ( 1996 +) as there is no room for a clutch fork ball stud on the later 5.600 diameter late bearing retainer.

 

[Winchested]

The oil is 100% still available from Mopar and GM. Was $30 a qrt though last time I bought it 2 years ago.

 

[Johnny Longrifle]

I've put several 100k of miles on NV4500's using BG SynchroShift fluid. Its completely priced with the Mopar and GM stuff.

With that said, OP's noise is not a fluid issue. I'm deaf AF and it sounds to me like rattlin blocking rings and/or syncro sleeves. Seems to shift ok though.

How about the clutch fork rattling around?

What do the shift forks and detent look and feel like?

 

[Oddball]

If it was an end play issue, it would show the most in third, cuz its closes to the pilot and thrust bearing where the input and main shaft meet. I was also thinking clutch like bad zuki suggested.

 

[The Freeak]

I've been testing it without the t-case. I haven't tested transfercase with no driveshafts yet, but compared to driving down the road it's a little quiter and most of the vibration goes away. I would assume this just has to do with it not having a load on it. I've already taken the t-case apart and found nothing wrong with it.


That would probably be my post lmao, I got it solved before I put the trans back together. All fits good now.

Ironic!


Just wondering - Is your output housing stock?

 

[tac1]

The oil is 100% still available from Mopar and GM. Was $30 a qrt though last time I bought it 2 years ago.

Word of caution on this GM PN 1234-6190 (the original nv4500 oil) is discontinued and gone from dealer inventory, if you ask for it they give you a new number for generic manual transmission and transfer case fluid that I'm pretty sure is just atf at $40 a quart.

I used the amsoil nv4500 stuff, but mine has 250k and already sounds like a dryer of rocks so your luck may vary.