New Tranny Mount=vibration

[dan1977p]

When I changed out my tranny mount for a new one, it raised up my rear output shaft from an 8* decline to a 4* decline but it didn't seem to add any vibes to my rear DS but I may have been in the perfect center of the angle sweet spot for my rig. If you have a way to measure your angles back there and shim your rear axle, you may be able to get back to normal. I'd change the bearing on that output shaft too if there is play as it could easily contribute to your vibes.

 

[brielly]

I finally broke down and took it to a shop. The shop claims its a vibration in the transmission and wants to drop the pan to check it out. My only concern is that when i ran it with only the front shaft it was as smooth as silk. I explained this to the shop's owner and he tried to tell me that without the rear shaft connected it wasnt under enough load to cause the vibration. The truck was used to tow so I'm sure the tranny has had some abuse but I'm a bit skeptical about this diagnosis. What do you guys think?

 

[Talyn]

The transmission doesn't know if there is a rear or front shaft connected. It will still see the same amount of rotational torque through the output shaft.

 

[xcm]

Did you get a centered, or offset mount? There are different mounts for different years, and I believe they'll both bolt up. The wrong mount would put a sideways angle on your propeller shaft.

Jaredatriot:

The 01 XJ takes a centered mount. To get an offset mount installed you'd have to get the driveline twisted a good bit.

IE, something that would cause problems...
Its possible...

You could also may potentially have reinstalled the trans cross member the wrong way... i dunno if itll bolt up for sure... but it might

 

[richamor]

I think I'd have a look inside the rear diff. Maybe a bad pinion bearing, carrier bearings, excessive backlash in ring/pinion. But....as mentioned checking that drive shaft for balance is a good place to start and work your way back.

The trans would be my last stop. If it were the problem I think you'd see more trouble than just vibration.

 

[wyowalsh]

the vibration probably was there the whole time but the new mount no longer has the slop so whatever is vibrating no longer has the the worn mount to absorb or mask the issue, I'd definitely make sure the parts removed for mount replacement were reinstalled in correct positions.

I'm in the auto repair business and this really does'nt sound like transmission,.
how did it shift" fluid color? has anything been done to the transmission?
these transmissions are'nt weak, and lower miles makes it hard to believe.

I'd get a 2nd opinion before opening up my wallet.......

can you get it up in the air somewhere and really look hard at everything?

I'd do that first

 

[brielly]

I cracked open the rear diff a few days ago and there was no metal shavings and the gears looked good. The tranny shifts fine and the fluid look good. I just changed it over the summer. I'm going to take my truck elsewhere. Its really hard to find anyonw honest in my area.

 

[davesdetail]

How about your exhaust pipe that runs through the trans cross member? Wedge a large screwdriver or a crowbar against the pipe where it goes through the cross member and see if it still vibrates, You may need to fix a hanger or re mount the down pipe at the manifold. Good luck.

 

[brielly]

I just rescued my car from the mechanic who I'm pretty sure was looking to rip me off. He wasnt too happy with me. After a 5 minute shouting match where he tried to get $120 from me for nothing I got the keys and split. He tried claiming my line pressure was low and that either the sun shell or tranny output bearing was bad. That just doesnt add up. I'm going to take the driveshaft to get balanced and go from there.

 

[davesdetail]

If the car ran smooth in park but began vibrating badly when you put it in gear, then this can't be the rear driveshaft. Check the tailpipe. I'm wondering if a hanger past the trans cross member is off or broke and it's rubbing on the cross member.

I changed the motor mounts but no dice. The engine ran smooth in park but began vibrating badly when I put it in gear. I didnt even bother going for a ride. I guess I'm pulling off the new tranny mount and possibly replacing it with another. Anyone have any other suggestions? I'm stumped.

 

[brielly]

I replaced the tranny mount tonight with a genuine mopar part. Its now running perect! The vibration in reverse and after hitting bumps was so bad I stopped driving until the part arrived. The parts look the same but if you look at the bracket that holds the exhaust, it has a small nub sticking out of it to help line up the parts. The mopar part has a hole to accompany this and the anchor part does not making it impossible to bolt the mount squarely to the bracket. I wish I had noticed it the first time around. Lesson learned! The mopar part was $100 more but worth every penny.

 

[Redsnake]

Interesting solution... Did you happen to take any pics of the 2 parts that shows the difference? I've had a similar vibration problem on my '01XJ and have never been able to pinpoint it. Also have done very similar part swaps including transmission and engine mounts. Perhaps I need to see what the Mopar Transmission mount looks like... I just attributed the new vibrations to my Brown Dog motor mounts, but it could be the transmission mount.

 

[brielly]

The parts look identical except the mopar part has an extra hole to accept the small pece of metal that sticks down from the exhaust bracket.

This is what the mount should look like. For whatever reason the anchor part didnt have the third hole.

 

[brielly]

If you look closely, you can see the piece sticking out of the bracket.

 

[kstopp]

Nice find!

My 93 doesn't have that same setup but I noticed that the Anchor mounts were a bit stiffer for the first few thousand miles, then they wore in a little and had less NVH.

 

[Redsnake]

Interesting and thanks for the pics. If it's 'only' a hole in the Mopar mount as pictured that allows for the small piece of metal/tab, wouldn't it work the same to just drill a hole in the Anchor mount and save the $$ by replacing it again f/the Mopar mount?

Since I've already got a 'good' transmission mount it'd be nice to save the cash. Now if I were to need a new transmission mount Mopar would definitely be the way to go.

 

[brielly]

Had I noticed the first time I would have drilled a hole but since I already had the mopar part I just bolted it on. The picture I posted is actually an aftermarket part (possibly crown) so I'm not sure if this was just a random mistake from the anchor brand or if they all come that way. It's definitely something to check before installing.

 

[Redsnake]

Very good information to know. And it could also be specific to the '00-'01 XJ's only.