NV3550 transmission grinds into third gear

[ToeKnee217]

Hi guys I have a 2002 Wrangler X with the NV3550 transmission. I recently noticed a small leak coming from the drain plug on the bottom of the trans so I decided to switch out the fluid and retighten everything. I used Royal Purple synchromesh and all of a sudden I have a grind into third gear. All other gears shift smoothly as it did before the change and It only really grinds at higher rpms. Would love some opinions/recommendations.

 

[bromel]

The NV3550 is very picky about fluid. The overwhelming advice you're going to see on this forum is to switch to Red Line MTL, which I can attest does wonders for the notchy grindy NV3550.

 

[Rubicon88]

Typical notchy jeep manual.

I would say it's coincidence more than anything. Will it grind in all rpm ranges?

However.....

Don't laugh.....

Did your seat move back one notch and not getting the pedal entirely pressed in? Floor mat preventing the clutch pedal from going all the way in?

I ask that because we fix this shit and you wouldn't believe some of the things that come in here and the why.

 

[Chris]

The NV3550 is very picky about fluid. The overwhelming advice you're going to see on this forum is to switch to Red Line MTL, which I can attest does wonders for the notchy grindy NV3550.

X2, I can't stress this enough. It loves Redline MTL!

 

[Jerry Bransford]

X3 on the Redline MTL recommendation, that's the best and most widely accepted lube for the NV3550 and NSG370. Not to mention I'm no fan of Royal Purple's overpriced lubes that are only purple due to the addition of a purple dye.

 

[ToeKnee217]

Typical notchy jeep manual.

I would say it's coincidence more than anything. Will it grind in all rpm ranges?

However.....

Don't laugh.....

Did your seat move back one notch and not getting the pedal entirely pressed in? Floor mat preventing the clutch pedal from going all the way in?

I ask that because we fix this shit and you wouldn't believe some of the things that come in here and the why.

haha no the seat is in the same place. Its only third gear that is doing it. If I slow down and allow the rpms to drop it'll smoothly enter third gear. In normal driving when I shift at around 2-3k rpm it grinds. Worked perfectly right before the fluid change.

 

[ToeKnee217]

Thanks for the recommendations I'm going to give redline a try. Seems impossible to find a dealer here in South Florida though. Auto Parts is a dealer but doesn't carry MTL so I guess ill have to order online and wait a couple of days. Hopefully its that simple but its mind boggling to think the fluid would cause only third to grind.

 

[KingCarGuyZ]

mine did this when I got it, 2 pieces of advice

1: Redline MTL (yes it really does help)

2: when you shift to 3rd "jog" or"fake" for 4th. so the 2-3 shift isn't diagonal or but kinda N-like. (if it's confusing ill draw a picture.)

my jeep has 250,000 miles. to my knowledge, it's on the original trans. I can't imagine the synchros are happy. but she still doesn't crunch 90% of the time if you're careful.

 

[Fonz54]

MTL and you have to finesse it when shifting. Slow and steady wins the race when shifting these transmissions.

 

[KingCarGuyZ]

Now that we talk about it, I think I have an extra 2qt's of MTL sitting on the shelf, It was actually cheaper to order 4 when I changed the fluid.

 

[ToeKnee217]

Just ordered MTL, should arrive on Sunday and ill give an update. Ive owned and daily driven this jeep for a couple months already so im quite accustomed to how it drives. I did try the fake 4th and straight into third approach but it doesn't help unless the rpms drop and then it engages smooth like before. The jeep only has 87k miles on it and the fluid that came out was clear engine oil color and consistency.

mine did this when I got it, 2 pieces of advice

1: Redline MTL (yes it really does help)

2: when you shift to 3rd "jog" or"fake" for 4th. so the 2-3 shift isn't diagonal or but kinda N-like. (if it's confusing ill draw a picture.)

my jeep has 250,000 miles. to my knowledge, it's on the original trans. I can't imagine the synchros are happy. but she still doesn't crunch 90% of the time if you're careful.

 

[KingCarGuyZ]

it doesn't help unless the rpms drop

uuuuh, I'm confused, what did you think was supposed to happen, your shifting? do you mean your trans crunches on a 4K shift? cause if so then yeah, I'm pretty sure all of ours do that.

you might try it and blip the throttle mid-shift, but that's normally a downshift thing.

 

[ToeKnee217]

Let me clarify since I guess I worded that response incorrectly. I've been driving manual for many years and am well aware that the rpms drop when you shift into the next gear. Im simply stating that if I go from second gear at 3000 rpms press the clutch and allow the rpms to drop excessively (1500 or below ) 3rd gear engages smoothly, if I shift normally the rpms would still be in the 2k range and it will crunch. I don't think I have ever pushed this car to 4k rpm.

 

[KingCarGuyZ]

Try the n thing (took me a while to get it) try redline, if that doesn’t work, maybe your shifting to fast. There not sports cars, take your time and figure out what makes your particular gearbox happy.

 

[Cotterpin]

I have a question. Does anyone think the shifter boot could play a role in shifting problems? Things like popping out of gear, grinding and worn synchronizers.
I’ve noticed when the temperature drops the boot gets stiffer and seems to keep pressure on the shifter. I’ve only had it pop out of gear when it’s cold out.

 

[KingCarGuyZ]

I have a question. Does anyone think the shifter boot could play a role in shifting problems? Things like popping out of gear, grinding and worn synchronizers.
I’ve noticed when the temperature drops the boot gets stiffer and seems to keep pressure on the shifter. I’ve only had it pop out of gear when it’s cold out.

That’s a really good point! I think mine got better when I replaced the internal shifter boot, but I did it for heat problems (like most of you)

 

[Cotterpin]

A shifter is intended to “float”, for lack of a better term.
Constant pressure, like resting your hand on the shifter while driving, can help wear out the synchronizers.
I was trying to figure out why my Jeep was popping out of gear on occasion and realized my shifter boot gets stiff when it’s cold out and like I said it seems to put pressure on the shifter sometimes to the point it will pop out of gear. But never does it when it’s warm out or when the Jeep gets warm inside and softens the boot up from the heater.
Just a crazy observation.

 

[Cotterpin]

On the same line as Rubicon88s post Another thing I found out was the clutch cylinder can go bad and eventually leak keeping the clutch from being depressed properly allowing the trans to continue to spin slightly and could also wear the synchronizers.

 

[ToeKnee217]

Received the Redline MTL and ended up making the switch today. Didn't make a difference in my case sadly. I am able to shift smoothly through all gears if I shift relatively early but as soon as I up the rpms to about 3k or above it'll grind into third and only third. Also grinds if I try to downshift into 3rd. It does not pop out of the gear or anything else.
I am not aggressively driving the car when this happens.
This jeep only has 87k miles but it looks like my synchro might be going out in that gear. Guess it was just a coincidence that it occurred all of a sudden when I changed the trans oil. Im going to start saving up for a possible new trans.
Thank you guys for your help.

 

[JDS123]

You should be able to bang shift the transmission at redline without grinding. The trans may not shift smoothly, but it should not grind. Not recommended to do so, but a trans with properly function synchros shouldn't grind.

Most likely your synchro is going out. I drove around with busted synchros on every gear besides 5th for a year+. You have to learn to match the speed when upshifting and rev match downshift. On downshifts, I usually just push to neutral, rev to the correct speed, clutch in, and then push into gear. Keeps everything smooth even when I essentially had no synchros. If you give the synchros no work to do by matching speeds, whether they are there or not does not matter.

I ended up swapping my NV3550 since I was moving to the city and no synchro driving in traffic just doesn't work well. If you end up swapping the transmission, get it from somewhere reputable. I ordered mine from JeepsUnlimited in Colorado and it is not a good transmission. Pops out of 4th on deceleration and pops out of second in 4low.