Please help! Noise in 3rd and 4th on in 4wd

scrmbln dirtbag

Kimchi Bio-fuel
City
Orange Park
State
FL
#1
I hate that every time I'm on here is to ask for help. Seriously one of these days I'll get another car so I can get this done properly. Anyways...

First big snow in Korea last night, so this morning on my way to work, I put it in 4H and off I go. I notice that in 3rd gear about 25mph I have this bit of "rattle" noise coming from under the jeep. Only when maintaining speed or deceleration. When shifting from 3rd to 4th I get a quick "rattle/grind" noise let out the clutch to give some gas and sounds like my driveshaft is gonna reach through the floor and slap me. Mind you this is all around 30mph. Is this normal. I read on the Jeep forum and someone stated they wouldn't go over 30mph in 4H anyways. But that doesn't answer what is wrong. Or, is this a normal thing? I've got the 2.5, 300t-case, dana 30. It does not make any noise in 1st and 2nd. I took it out oh 4H into 2H, hubs still locked and no noise. So is this a gear problem in my axle? Please help. 4wd is a must with my job!

Thanks,
Jeremy
 

AK-RWC

Legacy Registered User
SOA Member
City
south central
State
AK
#2
I think I can safely say that most of us joined the forum because A) we like to share, and B) we like to help! (Among other reasons, I'm sure.)

This is not normal. My initial thought is that it's a bad front pinion bearing or something about to let loose in the transmission. In 4H with a Dana 300, you shouldn't have any problems doing reasonable highway speeds. You need to do a little more diagnosis; from what you've told us, I can't yet determine if your problem is strictly speed-dependant, transmission gear dependant, transfercase dependant, axle dependant, or none of the above. Do you think it's coming from the back, the front, or right under the transmission tunnel? Is it a rattle, or a vibration? Have you tried 4H with the hubs unlocked? What about running through all the transmission gears in 4L? Do some obvious things like check all the driveshaft u-joints and pinion bearings by giving everything a good shake while the Jeep is in neutral (parking brake set, wheels chocked, etc., so the Jeep doesn't roll over you).
 

DirtyB

Crazy Cajun
LIFETIME
CJ-8.com Member
City
Port Allen
State
LA
#3
I agree with AK-RWC that you need some more trouble shooting. But, if you had the hubs locked while in 2H, then the front axel and drive shaft were spinning. Couple that with the fact that you didn't have problems in 2 wheel drive, and it smells like a problem with the transfer case.
 

scrmbln dirtbag

Kimchi Bio-fuel
City
Orange Park
State
FL
#4
More info/troubleshooting.

4L: hubs locked and unlocked, no noise or vibration. maybe due to lack of speed.

4H: hubs locked and unlocked, noise and vibration are light in 3rd compared to 4th (a lot).

2H: hubs locked and unlocked, no noise or unusual vibration through all gears.

The noise sounds as if it's coming from under the shifters/ under the tunnel.

Checked the U joints and there's slight play in the front (axel side). Sounds like it maybe the transfer case? I didn't have this noise before I put the lift on it that I can remember. Maybe the driveshaft angle is showing a problem I didn't know was there before?

PS. I understand the Q and A of the forum that's why I joined. Maybe someday I'll have more A's than Q's. LOL
 

AK-RWC

Legacy Registered User
SOA Member
City
south central
State
AK
#5
How fast did you get up to in 4L? In 4H, do you get any noise/vibration in first or second gear?

I agree with DirtyB: it's smelling like a gear problem related to 4H in your transfercase. If this is something you depend on, I'd stop driving it ASAP: drain the gear oil in the transfercase through a filter to watch for metal bits, and maybe pull the cross member and inspection cover to look for obvious broken things.
 

scrmbln dirtbag

Kimchi Bio-fuel
City
Orange Park
State
FL
#6
I think I got it up to about 20mph. Well, it's at 130K so I guess I'll just buy the rebuild kit. Thanks for the brainstorming guys.

One last question since I'm going to rebuild it. Twin stick? Or factory single? I understand the twin stick and having complete control over my axles, but is it really necessary? I guess my question is, when would I just need front wheel drive? Thanks

~Jeremy
 

spankrjs

Scrambler Junkie
LIFETIME
CJ-8.com Member
SOA Member
City
Biloxi
State
MS
#7
If I were you, I would change the U-joints first, especially since you said they had play:twocents:

A little bit of u-joint play will make a bunch of noise/vibration:crazy:

Besides, easier to eliminate the u-joint possibility by changing them, which is fairly easy, when compared to rebuilding a transfer case:thumbsup:

130K on a Dana 300 is not enough miles to warrant a rebuild, unless it was run low on oil :twocents:

If the U-joints don't fix the issue, check the rear output shaft bearings first before you pull the whole transfer case:twocents:
 

DirtyB

Crazy Cajun
LIFETIME
CJ-8.com Member
City
Port Allen
State
LA
#8
More info/troubleshooting.
I didn't have this noise before I put the lift on it that I can remember. Maybe the driveshaft angle is showing a problem I didn't know was there before?
You need to check your drive angles. I don't know exactly what you did with the lift kit, but if the drive shaft is out of phase with itself, that's a classic mistake.

Also, some people also purposefully increase the angle on the front drive shaft to relieve the angle on the back drive shaft. This is done with the idea that you basically always use the rear drive but only occasionally use the front.
 

scrmbln dirtbag

Kimchi Bio-fuel
City
Orange Park
State
FL
#9
I didn't do anything per say. I took it to a garage. There's no body lift just a 4inch lift with 1.5 shackles. That shouldn't have messed with it. And now that I'm typing this neither should have a body lift. Little tipsy at this point. :cheers: Well I ordered the U joints. Although the sound (to me anyways) sound like it's coming from the tranny/transfer case area, and the u joint was a little loose on the front of the shaft. But hey, It'll all get rebuilt at sometime. Just maybe not at the same time! Thank god I just got a higher paying job!
 

walkerhoundvm

Just trying to stay upright
LIFETIME
CJ-8.com Member
City
Cave Creek
State
AZ
#10
If the U-joints don't fix the issue, check the rear output shaft bearings first before you pull the whole transfer case:twocents:
Question - wouldn't the front output shaft bearings make more sense, since this is only happening in 4wd?

I completely agree with the U-joint idea, though. $40 for a pair of U-joints, 15-20min of your time, and you've ruled one big thing out.
 

scrmbln dirtbag

Kimchi Bio-fuel
City
Orange Park
State
FL
#11
Question - wouldn't the front output shaft bearings make more sense, since this is only happening in 4wd?

I completely agree with the U-joint idea, though. $40 for a pair of U-joints, 15-20min of your time, and you've ruled one big thing out.
Stupid question, but wouldn't the rear output bearings make the same noise when not in 4wd?
 

spankrjs

Scrambler Junkie
LIFETIME
CJ-8.com Member
SOA Member
City
Biloxi
State
MS
#12
Question - wouldn't the front output shaft bearings make more sense, since this is only happening in 4wd?

I completely agree with the U-joint idea, though. $40 for a pair of U-joints, 15-20min of your time, and you've ruled one big thing out.
Stupid question, but wouldn't the rear output bearings make the same noise when not in 4wd?
You would think so, but sometimes funny noise don't happen until something is "loaded up" a little bit more then usual, i.e. the additional drag from the front input shaft "could" be just enough to start some racket. That, and it is possible, if it only the rear output shaft bearings that are bad, to change them without dropping the whole case. For the front output, I am pretty sure you would have to drop the whole case. Being an internal optimist, looking for the easiest/cheapest fix first:thumbsup:
 

spankrjs

Scrambler Junkie
LIFETIME
CJ-8.com Member
SOA Member
City
Biloxi
State
MS
#13
You said it didn't make noise until after the lift was installed, that would lead me to believe you have a u-joint/drive shaft angle problem. When is the last time you greased the u-joints/drive shafts? Is there excessive play in the front drive shaft "slip joint"?

With the hubs locked in, 2wd, you said there is no noise? When you pull the front drive shaft to change the u-joints, drive it around in 4H. If no noise, most probably a drive shaft/u-joint issue:twocents: But, like I said earlier, sometimes stuff wont make noise until "under load".

Is there any "slop" present where the two parts of the front drive shaft meet? If so, fill it up with grease and see if the noise changes.

On my old CJ-7, it made bad noise at high speeds in 4wd due to excessive play at the front driveshaft slip joint, maybe that is your problem:shrug:
 

walkerhoundvm

Just trying to stay upright
LIFETIME
CJ-8.com Member
City
Cave Creek
State
AZ
#14
You would think so, but sometimes funny noise don't happen until something is "loaded up" a little bit more then usual, i.e. the additional drag from the front input shaft "could" be just enough to start some racket. That, and it is possible, if it only the rear output shaft bearings that are bad, to change them without dropping the whole case. For the front output, I am pretty sure you would have to drop the whole case. Being an internal optimist, looking for the easiest/cheapest fix first:thumbsup:

On top of that - it seems more likely for the rears to go since they're constantly strained. The front bearings only experience strain when you're in 4wd, which is maybe 1-5% of your driving time depending on how you use it.

Good to know :thumbsup:
 
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