Stevo1971

1993 XJ Sport 184,000 mi
So out of no where I’ve got a new issue. It started like this…
When pulling out from a stop the Jeep makes a strange fluttering noise.
Then moved on to this….
When pulling out from a stop and getting on it like onto a highway there is a vibration that grows stronger as the rpms increase, then goes away once transmission shifts to next gear. Repeats as rpm increases and stops when shifts into next gear.
I checked the tranny fluid level cold. Fluid was visible pretty far up. This appears to be the original tranny dip stick unlike the oil stick. The stick reads to check level while engine is hot and idling in park. I did this last night when I got home from work. There’s fluid on the tip of the stick but not where it needs to be.
Years ago I was reading on here that it’s best not to mess with Jeep trannys as something could go wrong with it all of a sudden.
I’m assuming and hoping I’m just low on fluid and can top it off through dip stick tube.

Any thoughts??
Thanks

Stevo1971

Also, about a week or so ago I noticed a vacuum tube that must have snapped from dry rot. There is air sucking in. This wasn’t the case before. I’ve had this Jeep 7 years and know it pretty well. Wondering if this may have anything to do with above issue.

Ricthewrench

Repair vacuum line first. Add atf. Go from there.

Stevo1971

Can’t seem to locate other end of hose. Don’t know if it’s gone forever or what. Did some googling and it may be related to the heat, a/c system.
here’s a couple pics

Looks like it’s headed back behind valve cover but I can’t find anything back there.

Chick-N-Picker

What you described in your initial post is almost for certain your transmission mount. Ask me how I know?

Tip: Buy a Mopar from the dealer. This is one of those parts that you do not want to go after market or you'll be replacing again, most likely. As I had to do. Never had an issue. Decided to replace motor and transmission mount. Everything was good. Then after a few an issue like you described arose and got worse and worse. Figured out it was the exhaust knocking on the cross member. Bought another transmission. Everything was great for a couple weeks and now it has come back and only getting worse and worse.

Did research and learned the Mopar part is the way to go. I have one that I'm putting in very soon. I really hope it is built better and it doesn't come back, because that knocking machine gun is so annoying.

Chick-N-Picker

Also if you want to find out if that is what it is. Just fold and fold and fold tin foil and shove it in between the exhaust pipe and cross member. Make sure it's good and tight.. Crank, drive and see if it's gone. If it is no longer knocking then you just found for sure that's it haha.

Stevo1971

Thanks for the response. Unfortunately, my exhaust has been knocking for years as the hanger broke a long time ago. I’ve gotten used to that noise.
The vibration is, at least I’m pretty sure, due to a sudden low fluid level.
Even though the Jeep is 28 years old I can still hammer down and do 0-60 in no time flat. With this new vibration I’ve only done it once and not doing it again until I fill the fluid back up.
Once I top off fluid level I’ll have to look for leaks. I only topped of tranny fluid one time in 7 years about 6 years ago.
As for the vacuum leak, I found the other end and will reconnect with electrical tape today.

Other end peeking out of firewall. This is why I have constant air coming out of the defrost vents.

agreen

When you're done denying the solid advice from ChickNPecker and find out that adding a little ATF isn't going to solve your vibration issue, crawl under and take a look.

You might find:
-bad engine mounts
-a bad transmission mount
-one or more bad U-joints

There are YouTube videos on how to check each.

Stevo1971

Im confused as to what issue you guys are addressing. If it’s the exhaust clanging on the cross member, that’s not my problem. That has been going on for years and still is. I’m speaking of something completely different. I can describe it again if need be but it’s the same as initial post. More of a growing vibration until gear changes.
With that said I picked up some tranny fluid (VI) today and when I went to top off the level was a little higher than last check so I didn’t add much. Will continue to monitor.

As far as vacuum tube, well it is difficult to wrap tape around both ends as there’s not much working room. Might use shrink wrap.

Stevo1971

And U joints are always a possibility 😂

agreen

A bad or sagging mount, such as a transmission mount or an engine mount, can cause driveline noises in a few different ways. One, as previously discussed, is the transmission mount making the exhaust rattle on the crossmember. Another is if the engine mounts are worn through (as is the case for about 7/10 of the jeeps I work on). It'll cause metal on metal contact. As in, there's so little engine mount left that the long bolt is now the only thing keeping the engine from flying out from under the hood. Another way is that when things droop, it can cause a change in driveline angle and could lead to the driveshaft(s) vibrating. And then, there's the U-joints. I've changed literal thousands of U-joints, and most of the time the customers don't even know it's a problem (or so they say). Then they'll drive it and come back later telling me they can now listen to the radio at a comfortable level now.

So crawl under and take a look. The transmission might shift a little better now, but you still had fluid indicating on the dip stick. It was fine.

Forgot to mention. I have seen a rare case of the tailcone bushing gone bad. That's only if it's 2wd and it's pretty rare. If it's 4wd, check the transfer case fluid level. That CAN cause a driveline grinding/vibe.

Stevo1971

Ok thanks I’ll take a look around. The weird thing is it started all of a sudden. Not over time, as you would think if bushings were rotting. My exhaust rattle is due to a broken hanger.
Thanks again for your response. I’ll update what I find ASAP.

Stevo1971

Finally had a chance to look into this. I crawled underneath and from what I can see ……..

A. The cross member for the tranny is solid. No dents, no missing bolts, no wriggling or play. Solid.
B. Tranny mount doesn’t look abused, or visually failed. Hard telling if it’s factory. But nothing sticks out as being an issue.
3. I put the Jeep in 1st gear (auto), chocked the wheels and pulled, twisted, pushed rear drive shaft. No visible wearing on U-joints. No noise other than that which comes from transfer case turning shaft back and forth. No extra play.
4. Checked rear diff. I’m going to need a gasket before I remove cover so stopped there. Located rubber fill plug.

While driving, the vibration seems to come from mid to rear under carriage, towards peak of rpm’s before shifting into next gear.

Ive attached a couple pics of what I did find. Now, I believe I’m leaking a little motor oil here and there from rear main seal. I know leaking oil can travel pretty far under carriage during in road operation. But I’m not convinced this “fluid” found all the way back behind tranny on other side of transfer case where the shaft connects to transfer case is coming from that.
I diagnose that I’ve got some kind of leak from transfer case cover assembly.
To see if I’m correct I can drain, fill transfer case, see if vibration abates and wait for it to return. If so, I will have to research what type of repair I’m looking at.
I’ve done all work to Jeep myself but haven’t messed with transmission issues. I still have front drive shaft to put back on after a friendly garage guy in town pointed to my origin of clanking up front last winter.
Also could someone verify my rear diff is a Dana 30? Pic attached also.

Any thoughts are appreciated

As a side note: I also reconnected vacuum lines with a small length of heat wrap. Burned the crap out of my finger tips with lighter due to no working room but it’s on. For now. We’ll see how long it lasts.

agreen

Transfer case rear output seal. It takes ATF, not engine oil.

How did the engine mounts look?

If your transfer case leaked enough, the chain might be slapping. Pull the front driveshaft and take it for a drive and see how it sounds.

Your rear axle is a D35

Stevo1971

What about rear output seal? Not sure what you are saying. Are you saying it looks like it’s leaking or? And yes, I’m aware it takes ATF. Thank you for making sure.
The front drive shaft is already off. Took off last winter due to clanking noise. Need to rebuild and reattach before this winter.
Did not check engine mounts yet. Will look at them tomorrow.
Thanks for identifying my Dana