NV3550 sound

[Kenneth G Zinis]

I've heard the NV3550 is characteristically noisey, not a trouble issue, just some sound.
What are the typical noises like, what speed does it occur, what gear, sound character, etc?
Mine sounds a little like clutch chatter when starting in 1st, usually just after clutch release, then it stops.
Are heavier than spec oils useful in quieting these?
I'm running Redline MTL

Thanks

 

[LieutenantJohnson]

that trans and the NSG370 is noisy. Usually throwout bearing noise and or gear noise. Just get used to it

 

[Wtrask]

Mine has made noise since I bought it brand new especially after a long drive it really growls in neutral. I got used to that what I can’t get used to is the damn synchros. I’m going to try red line MTL people seem to love it.

 

[Rubicon88]

I've heard the NV3550 is characteristically noisey, not a trouble issue, just some sound.
What are the typical noises like, what speed does it occur, what gear, sound character, etc?
Mine sounds a little like clutch chatter when starting in 1st, usually just after clutch release, then it stops.
Are heavier than spec oils useful in quieting these?
I'm running Redline MTL

Thanks

Mine has made noise since I bought it brand new especially after a long drive it really growls in neutral. I got used to that what I can’t get used to is the damn synchros. I’m going to try red line MTL people seem to love it.

The NV3550 is a noisy sumbitch.

Is there anything wrong with it other than noise?

@Wtrask
"I’m going to try red line MTL people seem to love it"

There are also many who had no change or worse results using Redline.

#1 if you've a bunch of miles on the tranny and no fluid change...any fresh fluid/lube will help.

#2 at the shop here i can tell you the last three instances of using Redline.
First was no change whatsoever.
Second was a change for the good but the fluid had never been changed in over 120k.
Third the tranny got worse by being more notchy than before.

 

[Kenneth G Zinis]

Mine has made noise since I bought it brand new especially after a long drive it really growls in neutral. I got used to that what I can’t get used to is the damn synchros. I’m going to try red line MTL people seem to love it.

What's issue w syncros? I changed to MTL and feels it's a little smoother, not dramatic, but an improvement. I just wanted fresh oil not knowing what PO did. Mine has B&M short shift kit, from PO, took a bit to get used to, gate is very narrow

 

[Kenneth G Zinis]

The NV3550 is a noisy sumbitch.

Is there anything wrong with it other than noise?

@Wtrask
"I’m going to try red line MTL people seem to love it"

There are also many who had no change or worse results using Redline.

#1 if you've a bunch of miles on the tranny and no fluid change...any fresh fluid/lube will help.

#2 at the shop here i can tell you the last three instances of using Redline.
First was no change whatsoever.
Second was a change for the good but the fluid had never been changed in over 120k.
Third the tranny got worse by being more notchy than before.

Hi, no issues really at all, just curious where noise comes from and easy ways to reduce if possible. When I changed to MTL, got slightly smoother. My rig has 80k, '03 Rubi

 

[Rubicon88]

Hi, no issues really at all, just curious where noise comes from and easy ways to reduce if possible. When I changed to MTL, got slightly smoother. My rig has 80k, '03 Rubi

And that's the thing...
Would genuine fresh fluid from mopar have done the same? Probably.

Without being there to hear it..throwout bearings make a racket too...

I will tell you this... the NV3550 while noisier than the others IMO is a tough S.O.B.
I'd take it over the AX-15...and honestly take either of those over the NSG370.

 

[Kenneth G Zinis]

And that's the thing...
Would genuine fresh fluid from mopar have done the same? Probably.

Without being there to hear it..throwout bearings make a racket too...

I will tell you this... the NV3550 while noisier than the others IMO is a tough S.O.B.
I'd take it over the AX-15...and honestly take either of those over the NSG370.

I know, it feels rock solid!

 

[Superjay5]

Mine makes at racket in neutral and the clutch out, throw out bearing…. Other then that it’s quiet.

I did change my fluid to redline. It did smooth out the shifting a little. It wasn’t bad before the fluid change, but it did make a noticeable change. As mentioned above not sure if the redline helped or just the new fluid.

mines been making the throw out bearing noise since I bought it about 60,000 miles ago… I’ve thought about changing it out, but seems so common that I suspect a new bearing will do the same in short order

 

[Nomader]

Just did full luk clutch kit in my 04 everything including master and slave. My throw out bearing still makes noise. I figure it's normal.

 

[bromel]

Mine makes at racket in neutral and the clutch out, throw out bearing…. Other then that it’s quiet.

I did change my fluid to redline. It did smooth out the shifting a little. It wasn’t bad before the fluid change, but it did make a noticeable change. As mentioned above not sure if the redline helped or just the new fluid.

mines been making the throw out bearing noise since I bought it about 60,000 miles ago… I’ve thought about changing it out, but seems so common that I suspect a new bearing will do the same in short order

That noise is not the throwout bearing. The throwout bearing is only engaged when you press down on the clutch and the TOB contacts the pressure plate to separate the clutch disc and flywheel. When it goes bad, you hear a screeching sound when pushing down on the clutch; otherwise it's not spinning.

The racket in neutral is just typical gear rattle that you hear because the TJ has no soundproofing, and also because the NV3550 is a noisy sumbitch.

 

[brewtus98]

Changed mine to Redline MTL with about 11k on the odometer. I have noise clutch out and goes away with clutch in. It sounds just like input shaft bearing rolling along. Wasn't notchy or hard shifting prior to change from factory fill, but definitely better when colder outside now. Just living with the noise. Have to assume it has been that way since new with so few miles on it.

 

[ColoJeep]

I have both 5 spds. AX-15 and the NV 3550. The NV 3550 IS a noisy sum bitch! It does have a lower first gear then the AX-15,
But then makes up for that with a reverse ratio set up for Bonneville. It's Normal for what it is.
The Aisin trans is much smoother and quieter, and I suspect it will be around long after the 3550.
They served Toyota and Jeep well for many years.
The switch from the AX-15 to the NV 3550 was likely a cost saving move, not increased durability .
Kind of like changing out the Saginaw Steering box out for the made in India "Mercedes " box.
Funny how the "big bore " steering builders don't make a kit to put the "Mercedes " box into the earlier jeeps.
Just crank up the radio before you start up the TJ!

 

[Superjay5]

That noise is not the throwout bearing. The throwout bearing is only engaged when you press down on the clutch and the TOB contacts the pressure plate to separate the clutch disc and flywheel. When it goes bad, you hear a screeching sound when pushing down on the clutch; otherwise it's not spinning.

The racket in neutral is just typical gear rattle that you hear because the TJ has no soundproofing, and also because the NV3550 is a noisy sumbitch.

I assumed with no load on the bearing with the clutch out that it allowed the TOB to rattle around like crazy. With a load it quiets down. But yes it should not be spinning with it in neutral… hmmmm. I assumed wrong, just sounds like a bearing noise. It’s loud regardless

 

[Danno4x4]

I just posted in another thread about resolving my stiff shifting in the NV3550 but I figure I would post my findings here too in case it helps somebody who has been wondering about the “box of rocks” sound that the NV3550 makes with the clutch out idling in neutral.

I’ve owned my 2001 Wrangler since new and always used Mopar-spec fluid. Over many years, the shifting gradually became stiffer and stiffer until I practically had to yank it into gear — especially when cold and particularly coming out of 3rd gear.


Once the Jeep warmed up, it would improve somewhat.


Like many people, I tried several things based on forum recommendations:

• Switched to Red Line MTL
• Did a kerosene flush
• Followed the common “rear wheels off the ground, run through gears at idle” procedure

Those things helped a little, but I was FINALLY able to get the transmission shifting smoothly again a few months ago. Along the way I discovered a few interesting things.


(Some of the below is my personal opinion/theory, so take it for what it’s worth.)


Observations


1) The “box of rocks” NV3550 noise


Since the Jeep was new, the transmission always made the familiar “box of rocks” rattling sound while idling in neutral.


I brought it to the dealer early on and was told this was normal NV3550 behavior. Every other Jeep I rode in with an NV3550 seemed to sound the same, so I accepted it as a quirk of the transmission.


2) I could never get the full 2.1 qt capacity into the transmission


Every fluid change, I drained it normally and refilled through the fill plug until fluid ran back out.


But I was NEVER able to get the full stated 2.1 qt capacity into the transmission.


I assumed some old oil simply remained trapped in the case after draining.


3) I think the shift rails/fork bushings were gummed up


This video basically describes what I think was happening in my transmission:



View: https://youtu.be/a80xPwmqBv4?si=Yc52z3AbUfumq_8t


My theory is that the shift fork bushings and/or shift rail supports had become coated with varnish and grit over time, causing the rails to drag.


I also found Chrysler TSB 21-003-01 (REV A), which discusses high shift effort related to the detent plunger.





What I Actually Did


Step 1 — Removed the shifter and detent components


I:

• Drained the transmission
• Removed the transmission access panel
• Removed the shift tower
• Removed the detent plug, spring, and plunger

Interestingly, with the detent plunger removed, the shifter was STILL very stiff.


The only difference was the shifter no longer had the “snick-snick” detent feel between gears.


So personally, I don’t think the detent plunger was my primary issue.





Step 2 — Aggressive kerosene flushing


I poured an entire gallon of kerosene into the transmission through the shift tower opening.


Yes — a gallon. Nearly double the transmission capacity.


My goal was to get the internals completely flooded and splashing aggressively.


I then:

• Put the transfer case in neutral
• Started the Jeep
• Ran the transmission in 4th and 5th gear at ~2500 RPM for about an hour

Every few minutes I worked the shifter through all gears repeatedly.


Afterward I drained the kerosene.


The first drain came out light brown.


I repeated this exact process two more times.


By the third flush:

• The kerosene drained nearly clear
• The shifting had started improving noticeably

Step 3 — Cleaned the shift rail area


After the second flush, I sprayed carb/choke cleaner into:

• the detent bore
• the shift rail area
• the front rail support area

While doing this, I repeatedly worked the shifter back and forth.


My goal was to dissolve as much varnish and sludge as possible from the shift rail supports.





Step 4 — Drying the transmission


After the final kerosene flush, I:

• Used strips of shop towel through the drain hole to soak up residual kerosene
• Used a heat gun on LOW to blow warm air through the transmission for about an hour

Probably overkill, but I wanted as little kerosene remaining as possible.





Step 5 — Refilled with Red Line MTL


I initially filled through the fill plug with Red Line MTL.


Even then, I STILL could not get the full 2 quarts in before fluid ran out the fill hole.


I ran the transmission again for about 30 minutes through the gears.


At this point:

• shifting was dramatically smoother
• BUT the familiar neutral rattle was still present

Step 6 — Final refill from the TOP


I then:

• Drained the fluid one final time
• Reinstalled the detent parts using moly grease per the TSB
• Measured EXACTLY 2.1 quarts of Red Line MTL
• Filled the transmission THROUGH THE SHIFT TOWER OPENING instead of the fill plug

This ensured the full factory fluid capacity was actually in the transmission.





Results


Immediately afterward:

• The shifter felt almost like new again
• Cold shifting improved massively
• The stiffness was basically gone
• AND the “box of rocks” neutral rattle completely disappeared

That last part shocked me.





My Personal Theory


I suspect the NV3550 may have a design quirk where filling through the side fill plug does not actually allow the full 2.1 qt capacity to be reached.


If true, that could mean many NV3550s have unknowingly operated slightly low on fluid for years.


I think the combination of:

• slightly low fluid level
• age
• varnish buildup

may contribute to the stiff shifting these transmissions develop over time.


Time will tell if the issue returns, but from now on I will only fill mine through the shift tower opening using the full measured capacity.


Was all of this overkill? Probably.


But after years of progressively worsening shifting and trying multiple fixes that only partially worked, this was the first thing that truly solved it for me.

 

[GoldenGorilla]

I just posted in another thread about resolving my stiff shifting in the NV3550 but I figure I would post my findings here too in case it helps somebody who has been wondering about the “box of rocks” sound that the NV3550 makes with the clutch out idling in neutral.

Huh. Cool. I guess I could drive the left side up on ramps to top it off? Explains the ocassional comment about a new owner opening the fill plug to find gear oil dumping out.

 

[MaxKray]

Я только что написал в другой теме о решении проблемы с тугим переключением передач на моей коробке NV3550, но решил опубликовать свои выводы и здесь, на случай, если это поможет кому-нибудь, кто интересуется звуком «коробки камней», который издает NV3550 при отпущенном сцеплении на холостом ходу в нейтральном положении.

Привет! Я только вчера наткнулся на ваше сообщение. Два года меня беспокоил шум, исходящий от моей трансмиссии NV3550. Сегодня я долил масло, и шум исчез. Это действительно работает!