02 TJ 5-Speed Bucking When Getting into First Gear

[KCNoDots]

Okay so I just thought I would throw this out to you guys and see what comes of it.

I have a 02 TJ 5spd 4.0. The transmission grumbles when I am sitting in N and when I turn it off. Once I press the clutch the grumbles go away.

The weird issue I am having is when I am sitting in stop and go traffic for a while, or just in a situation where I am using the clutch repeatedly and often, that when I go to put it into first and begin slowly letting out the clutch (while pressing the gas slowly) the TJ seems to buck forward a few times before it gets into 1st. Sometimes when it starts to buck I will just quickly release the clutch fully and it will stop the bucking.

It may do this 1-3 times, then if I drive for 5 minutes without having to press the clutch it wont buck the next time I am putting it into 1st gear.

Note: I usually shift out of first and into N whenever I come to a stop, I almost never just sit somewhere and hold the clutch down. and this only happens going into 1st gear.

I'm not sure if this means the clutch is going out, is the clutch getting over-worked? or what? What are the symptoms I would have if the clutch was going out? or over-worked?

Thanks everybody for any insight!

 

[danof76]

My guess is clutch issue. If it grumbles in neutral with the clutch engaged (pedal up) but not when the clutch is disengaged (pedal down) then there's something in that connection that's possibly not making good contact. What doesn't make sense to me there is why it would go away after a few times. Maybe it somehow corrects itself after a few times, have you tried pumping the clutch periodically while parked, in neutral to see if it makes the "grumble" go away?

Also, are you sure this isn't any sort of engine issue? Does it happen in low RPMs in different gears? Have you tried letting the engine just warm up to normal operating temperature before moving it from a cold start to see if it goes away?

A bad clutch can be either the smell of clutch (you'll know it, it's nasty), odd noises/vibrations like rattling near your feet or the clutch slipping sometimes (loss of power, RPMs going up). One rudimentary way to test the clutch is to get the vehicle moving then dump the clutch to see if it does a sharp engine brake. Not sure if that's a great idea given your current predicament as it could make things worse.

 

[danof76]

Also, just to make sure, you haven't changed anything recently, have you? Like within the last 1,000 miles, let's say. Anything related to engine, suspension, drive-train, etc.? Anything at all, even fluids. Just checking...

 

[KCNoDots]

My guess is clutch issue. If it grumbles in neutral with the clutch engaged (pedal up) but not when the clutch is disengaged (pedal down) then there's something in that connection that's possibly not making good contact. What doesn't make sense to me there is why it would go away after a few times. Maybe it somehow corrects itself after a few times, have you tried pumping the clutch periodically while parked, in neutral to see if it makes the "grumble" go away?

Also, are you sure this isn't any sort of engine issue? Does it happen in low RPMs in different gears? Have you tried letting the engine just warm up to normal operating temperature before moving it from a cold start to see if it goes away?

A bad clutch can be either the smell of clutch (you'll know it, it's nasty), odd noises/vibrations like rattling near your feet or the clutch slipping sometimes (loss of power, RPMs going up). One rudimentary way to test the clutch is to get the vehicle moving then dump the clutch to see if it does a sharp engine brake. Not sure if that's a great idea given your current predicament as it could make things worse.

Thank you for your input!

I had read before on this forum, possibly from @Jerry Bransford himself, that the NV3550 is just a noisy truck transmission and that the light grumbling when sitting in nuetral, pedal up, was normal for it.

And yes when the pedal is pressed down, the grumble noise is gone.

It only happens going from stopped to 1st gear. never any other gear no matter the RPMs. Maybe I am just not giving it enough gas sometimes, but it really feels like it shouldn't be bucking when I am giving it over 1000 RPMs while trying to take off from a stop. (I know that the 35" tires and 3.73s don't help though. And as a bonus note: I dont remember this ever happening when I was on 31" tires and 3.73s.)

The bucking never happens cold. It is only when warmed up. that is what makes me think maybe it is getting over heated or over worked, then once it 'cools down' it is just fine. And it doesn't even happen all of the time. Maybe I am making mountains out of ant hills I just wanted to see if I was missing something that was happening (to prevent worse things from happening).

Maybe I just need to change the fluid to Redline. I am not sure what fluid is in it or how old it is, but it does not look bad.

 

[KCNoDots]

Also, just to make sure, you haven't changed anything recently, have you? Like within the last 1,000 miles, let's say. Anything related to engine, suspension, drive-train, etc.? Anything at all, even fluids. Just checking...

Yes, I did a 3" suspension lift, 1.25" body lift, beefed up steering, and changed to 35" Tires. I have NOT regeared yet, which makes me think maybe the trans is getting over worked with the 35s and 3.73s? (and the fact that I use the clutch a lot because I shift to N at every stop instead of staying in gear and holding the pedal down. It never did this when I was on stock suspension and 31s.

 

[danof76]

My NV3550 has a slight grumble as well, but nothing I have ever considered alarming or even notice much. If that hasn't really changed before and after the suspension work I wouldn't think anything of it. Only time "bucking" happens to me is a drop in RPMs and the Jeep isn't moving fast enough: something I'm sure you know that can easily happen when you're trying to creep in first, but certainly nothing I ever see when taking off.

I think I initially misunderstood and figured it happened cold, not hot. My bad.

I doubt suspension would have anything to do with it... but you never know. Have you checked to make sure everything is still torqued down? How long has it been since you did all that work? Also, how many miles are on it so far?

Hey, maybe it is overworking the transmission and the clutch is slipping periodically. However you'd likely smell burning clutch if that's the case. Just to check all around try to see if you can make a stop as soon as possible after it happens, get out and see if there's any funky smell (see a smell... what?)

I'd honestly be concerned about something engine related more than anything if you don't feel any other loss in power while driving... other than the general loss in power you'd feel running 35s on 3.73s. Have you tried seeing if there's any codes at all? Even if you don't have an engine light it's still worth looking to see if it says anything. Again, you never know, it could coincidentally be an O2 sensor that went out recently.

Edit: checking a few posts here and elsewhere, anyone that describes a "bucking" from the TJ seems to all solve the issue by replacing one of their O2 sensors. Just a suggestion.

 

[KCNoDots]

My NV3550 has a slight grumble as well, but nothing I have ever considered alarming or even notice much. If that hasn't really changed before and after the suspension work I wouldn't think anything of it. Only time "bucking" happens to me is a drop in RPMs and the Jeep isn't moving fast enough: something I'm sure you know that can easily happen when you're trying to creep in first, but certainly nothing I ever see when taking off.

I think I initially misunderstood and figured it happened cold, not hot. My bad.

I doubt suspension would have anything to do with it... but you never know. Have you checked to make sure everything is still torqued down? How long has it been since you did all that work? Also, how many miles are on it so far?

Hey, maybe it is overworking the transmission and the clutch is slipping periodically. However you'd likely smell burning clutch if that's the case. Just to check all around try to see if you can make a stop as soon as possible after it happens, get out and see if there's any funky smell (see a smell... what?)

I'd honestly be concerned about something engine related more than anything if you don't feel any other loss in power while driving... other than the general loss in power you'd feel running 35s on 3.73s. Have you tried seeing if there's any codes at all? Even if you don't have an engine light it's still worth looking to see if it says anything. Again, you never know, it could coincidentally be an O2 sensor that went out recently.

I will look into all of this. Thank you for your reply, seriously!

I will check for codes too. I have no check engine light however. I have never noticed any foul smells at all so maybe I am just over thinking it! lol!

I only have about a thousand miles (about 50 days) on the whole install and tires, so not very much.

It does only happen at low RPM when starting off from a stop.

I'll update if I find anything else out!

 

[The powerlineman]

Okay so I just thought I would throw this out to you guys and see what comes of it.

I have a 02 TJ 5spd 4.0. The transmission grumbles when I am sitting in N and when I turn it off. Once I press the clutch the grumbles go away.

The weird issue I am having is when I am sitting in stop and go traffic for a while, or just in a situation where I am using the clutch repeatedly and often, that when I go to put it into first and begin slowly letting out the clutch (while pressing the gas slowly) the TJ seems to buck forward a few times before it gets into 1st. Sometimes when it starts to buck I will just quickly release the clutch fully and it will stop the bucking.

It may do this 1-3 times, then if I drive for 5 minutes without having to press the clutch it wont buck the next time I am putting it into 1st gear.

Note: I usually shift out of first and into N whenever I come to a stop, I almost never just sit somewhere and hold the clutch down. and this only happens going into 1st gear.

I'm not sure if this means the clutch is going out, is the clutch getting over-worked? or what? What are the symptoms I would have if the clutch was going out? or over-worked?

Thanks everybody for any insight!

Time for a new clutch sounds like to me, the throw out bearing is presumably what is making the grumbling noise while the clutch is not depressed, and there I would think be a pilot bearing also. I dont know the 3550 well but that's common in all I've owned.

Sent from my SM-G930V using Tapatalk

 

[Jerry Bransford]

It's normal for our Jeep transmissions to make a spinning bearing-like sound when the transmission is in Neutral, the engine is running, and the clutch pedal is up. All that sound is the transmission's input shaft and bearings being spun by the engine. That sound, when the clutch pedal is up, is absolutely normal and does NOT indicate any issue with the throwout bearing. The throwout bearing only spins when the clutch pedal is being held down with your foot. So if the sound is there when the transmission is in Neutral, the engine is running, and the clutch pedal is up but the sound goes away when you step down on the clutch pedal, it's absolutely normal.

 

[KCNoDots]

So... ignoring the light grumbling sound while sitting in N, since Jerry has made it clear it is normal. The bucking has happened a couple more times since my last post.

Once while I was in a very long slow moving drive through. After about inching up 5-6 car lengths, as I had the shifter in 1st and was slowly letting out the clutch and giving it some gas, it began to buck, buck, BUCK so I pushed the clutch down all the way to stop the bucking. If I push the clutch all the way to the floor, or release it completely, then the bucking stops immediately. After sitting for a few minutes I went to shift into first slowly again and it was fine. It seems to only happen after repeatedly using the clutch in and out in and out. I dont usually feather it. I put it in first, go a bit, then put it back to N.

The next time I was off-roading in Box Canyon near Florence, AZ. There was a steeper, rocky, climb I was going up. I had to be on and off the clutch pretty repeatedly in order to work my way up the lines. Towards the end of the clumb, I was easing into 1st from N, slowly giving it gas, and again it started, buck, buck, BUCK, BUCK, BUCK!! it launched the TJ forward pretty good on that last buck, a rock grabed the tire and cranked my steering wheel to the left. I let out the clutch immediately as that happened (I was still in 1st so it died). I waited about 3-5 minutes and I checked the Jeep because I was afraid I slammed something into a rock or broke something. When I restarted the Jeep, I backed up a bit because I was lodged between a couple rocks I did not want to be between. Afterwards I put it into 1st and it was fine. I was in gear and walked right up the last rocky slope.

Somebody please tell me what could be causing this? Never happens in anything other that creeping from N-1st gear. and only when the clutch seems to be used more rigorously. No burning smell. The TJ otherwise shifts great always every other time, and drives really well. Jeep has been maintained very well throughout its life.

Over-worked clutch? Over-heated clutch? Would switching to new Redline MTL fluid possibly help? Maybe the fluid is just old and not cooling as good?

I'll attach pics from wheeling from my phone below

 

[Diegoval0812]

Hey, did you ever figure out what the issue was, I am having a very similar problem with my Jeep Wrangler. Funny enough mine is a 99’ but looks just like yours, red wrangler sport.

 

[Goatman]

Possible that the hyd clutch is allowing fluid leak by at the clutch master cylinder? If you use it too often the result could be incomplete clutch disingaugement. After a bit of no use the fluid will seep back into the proper side of the master cyl. Similar to how when the brake master cylinder will need to pump the brakes at a long light and will slowly let the brake pedal slowly drop to the floor. Just a guess. But that is similar to a non hyd clutch needing the linkage adjusted for clutch wear.

 

[KCNoDots]

Hey, did you ever figure out what the issue was, I am having a very similar problem with my Jeep Wrangler. Funny enough mine is a 99’ but looks just like yours, red wrangler sport.

So it wasn't happening all of the time. But it rarely happens now. What I changed was my driving habits.

I used to always push in clutch, shift into N, and let out clutch at a stop. Only to have to push in clutch, shift to first, then let out clutch to get going. That is 4 clutch movements at every stop and go. Now I simply push in clutch and hold in, once I need to go I let out clutch and off I go.

It has not bucked since then and I think it is because the clutch is being used less frequently and not getting as hot. YMMV.

 

[Goatman]

Sounds more of a synchro issue. Those extra pedal movements in and of them selves shouldn't cause a problem. But if it cures the issue then it's a win in my book.

 

[InfamousCanadian]

I know that when I first got my Jeep if I didn't give enough of the skinny pedal on take off I would get a bucking. After a while and just getting better at manipulating the clutch in the Jeep I haven't had the issue in over 2 years of daily driving.

 

[g.hayduke]

If you are going to re-gear, and sounds like you need to, get that done and see where things are.

Holding the clutch in will wear out the throwout bearing prematurely. The bucking is happening when you let out the clutch when it's already in gear, correct? If so, it's not a synchro issue which would only possibly impact getting it into gear or shifting between gears, nothing to do with what happens when you engage the clutch.

Your phrasing is a bit confusing though: "this only happens going into 1st gear". This sounds like you're shifting into first gear. But if you're talking about something that happens when you let the clutch out, you are already "into 1st gear", not "going into 1st gear".

 

[ranger101]

Sounds like you should invest in a new clutch master/slave assembly. The clutch isn’t disengaging completely which is causing it to buck like that.

 

[TurboTJ]

When I put a Barnes skid plate on that raised the transfer case one inch I started to experience bucking when engaging the clutch in first and reverse. Then I put a double Cardan rear drive shaft on, got the angles more or less correct and the bucking went away. I think if your driveshaft angles are not correct, or just excessive angles, that in addition to vibration at speed you may experience bucking with a manual transmission.

 

[Goatman]

Sounds like everyone is thinking your post means something different. Are you staying in first and repeating clutch movement? In neutral and double clutching? Try another explanation of what is going on so we can get a better idea what and when the issue happens.

 

[KCNoDots]

If you see post #13, I dont really have this issue anymore. But thank you for commenting and offering your help