acer99

Hey guys,

I have a 2000 XJ with an AW4 automatic and it has a vibration/rumble in 4th gear. Got 145,000 miles; no idea if the transmission is original or a junker replacement since I picked up the Jeep about 60k miles ago.

The vibration/rumbling was much less noticeable and I put up with it because... its a Jeep... its supposed to make noise.

Anyhow, I've since put a 5.5" lift, rebuilt the front suspension, added a SYE, added 31" tires and replaced the rear driveshaft with a new one.

I've also done a partial fluid change, replacing with Dex 3 for high mileage cars.

The vibration and rumble only occurs in 4th gear, otherwise its quiet and smooth.

Any ideas?

Thanks!

VTJeep

Hmm.. Maybe exhaust hitting x member? Is rear axle shimmed? Any more details on the noise itself? What kind of axle did you use in rear? DC shaft?

acer99

Rear axle is a junker replacement, but its an 8.25. When I did a rear disc brake swap and had the pumpkin open, the gears looked to be in great condition. I didn't find any shavings or metal.

When I replaced the rear drive shaft, the u-joints were in really bad shape. Actually, I unbolted one side and the whole thing fell apart. Whew!

I put an Adam's driveshaft in place: http://adamsdriveshaft.com/

Not sure on the exhaust idea... its an interesting one though. The end is cut short to make room for the shackles. I'm not having any other strange effect for different RPMs in different gears.

It's hard to describe the sound exactly. It reminds me the grindings that bad bearings make before they go out. The vibration isn't like death wobble... I've experienced that and its nothing the same. Its more like drifting off the side of the highway and driving on the roughed up part of the road to wake up tired drivers.... but not as harsh.

VTJeep

Haha.. I actually meant to as what kind ok shaft you used, not axle, but you answered that already.. So I'd still wonder if the rear axle needs shims, with the SYE and cv shaft, the shims are sometimes needed. Have you checked both shafts for play? The rear shouldn't be an issue, but ya never know.. It's not in the front somewhere is it? Bearings, hubs? Dunno..

acer99

Had a problem with r/f hub a couple of years ago and replaced it. Not the same sound.

I hear a "clunk" in the front when I'm braking and turning, and my suspicion is that its the u-joints on the front drive shaft. There is a little bit of rotational play when I turn it, but not much. I figured that was normal but I wonder.

I haven't disconnected the front drive shaft to test to see if the sound goes away, and I should. It just seems strange to me that the noise/vibration starts immediately when the tranny shifts into overdrive.

Where would the shims go on the rear drive shaft? Between the connections so it becomes a 1/3" longer or something?

These drivetrain issues are such a PITA to figure out.

redmuck

maybe the bearings in that jy axle are going bad. check your trans/transfer case mount to see if thats bad. could be the pinion shaft bearing too. my mount was bad and when rpms goe up, the motor and trans was pushing down on the driveshaft and whole axle a little to much. the mount should barely move.

Aljay

I had a simiular issue when I was stock height turned out to be slip yoke was dry on front drive shaft. Like the other guys said tho could have a bad axle or bearing. I thought I found my problem when I rebuilt the D35 (yeah I know it was a waste to fix it) in my jeep the axle was all kinds of fubar where the bearing rides on the axle.

acer99

I'll disconnect the front drive shaft and test it. Need to make sure that thing isn't going to fall off at some point soon anyhow.

I also need to service the front axle in general. I've never changed fluids on it.

The transfer case looks to be in pretty good shape. When I disassembled it for the SYE install, there was a bit of metal dust on the magnet, but otherwise it looked good. I didn't see any scoring or scratching anywhere.

The sound and rumble sounds like its coming directly from the transmission.

Is there any possibility that there is something messed up with the over drive gear?

What about the torque converter? Is that something that can rumble a bit when it gets "locked"? (I think that happens in over drive).

VTJeep

See what happens when you remove the front DS. If it goes away, hit the JY and grab a "new" shaft. If not then continue to inspect and fix an front end issues. I doubt it's the tranny, but how is fluid? I believe you check it when up to temp,
With engine running, in neutral. Nice and red? Doesn't smell bad at all?

acer99

The last time I changed the ATF, it smelled nasty. I don't have a lot to compare it to as it was my first time actually doing it, but it smelled burnt.

My original 4.0 blew up on me a few years back, and I've since come to realize that the ATF runs through a cooler in the radiator and is prone to overheating if the rest of the engine is.

The advice I got was to slowly change the ATF, so that's what I've been doing. I plan to do a full change by disconnecting the transmission fluid line from the radiator and draining into a bucket while I add fresh fluid.

I used the Valvoline DexIII/VI for high mileage vehicles last time since I saw a lot of guys on here say not to use the ATF 3+. I guess the ATF has a lot to do with how the torque convertor locks up.

Also, I'm wondering now if I'm dealing with "torque converter shudder":
http://www.agcoauto.com/content/news/p2_articleid/203

Since my fluids weren't changed regularly, and my filters are probably original, then it might be possible that my clutch is worn out.

acer99

In retrospect, its probably not torque converter shudder. I saw a Youtube video with someone driving when it starts, and that is not what I'm experiencing. There isn't any shaking, it just a vibration.

VTJeep

Done the basics yet? Any new ujoints and grease on fittings?

acer99

Not yet. Always have to negotiate for garage space with the significant other.

The result of a few too many Jeep projects that will only take a few hours turning into a few days.

VTJeep

Ahh.. Right on, understood.. In due time then, haha.. At least this is a project to keep it running strong! Keep us posted.

acer99

I know it's been a while, but here's the update, and some recapping so the thread doesn't have to be reread:

I did a partial flush with the recommended DEX, meaning I drained the transmission pan and refilled. I drove on that for about 6 months.

I'd been reading about some guys using AT4, so I did a total drain by disconnecting the line to the transmission cooler in the radiator and letting the fluid drain into a bucket while I refilled with fresh, synthetic AT4.

As I drove it like that, maybe for two or three weeks, the transmission just felt funny when changing gears, like it was slipping a bit. I noticed I'd been dripping fluid so I checked my level, it was low, so I topped it off.

Drove for a while, still didn't like the way it felt, so I decided to switch back to Valvoline High Mileage DEX. I did a total drain with the disconnected line and refilled.

I also replaced the transmission filter, which was completely clean, and looked at the magnet in the bottom of the pan, which had some very fine dust but nothing remarkable.

I drove for a while, still saw the drip but couldn't find it, then decided I wanted to add a secondary transmission cooler.

I disconnected the line to the radiator and ran it to a new cooler in front of the radiator. At about the same time, I reflashed my ECU with a custom tune using an SCT controller.

After the flash was done, the CEL came on. I read the code using the SCT and I got a P0700 and another code that meant the transmission fluid was taking too long to warm up.

About a week later, I replumbed the transmission cooler line to first go to the radiator before going to the secondary cooler. I also found the leak: the connection to my aftermarket radiator was loose, so I fixed it.

Today, I shorted the electrical to reset the ECU and turned the key on but engine off. The CEL came on again. So I cleared the code with the SCT over and over, but now only P0700 comes on. Engine is never on, this happens with just key turned on.

Flashed the ECU back to stock, CEL comes on. Flash back to custom tune, CEL comes on. Still, never turn engine on.

Drive around for a bit, come back to the garage, clear the CEL code and time how long it takes for CEL to come on for P0700: 10 seconds like clockwork, engine is never turned on. Also, the code for the transmission fluid not warming up quick enough has not returned.

And lastly, the rumble is still there, but it seems to have gotten a bit better. I checked for any play with the front drive shaft and I can't feel any... its very tight.

I don't notice anything out of the ordinary going on. I cleaned and greased the connections to the NSS, made sure the backup lights go on when in reverse. I replaced the TPS back in November, and the TCU was replaced in July.

There isn't any strange behavior with the transmission other than the slight rumble while on overdrive, and the dang P0700 transmission code tripping the ECU.

Anyone got any suggestions????