jacob.

ok so when i put my 92 xj automatic in drive it makes a loud clunk and lurches forward same in any other gear . has new u joint .what could it be ?

Mykal

Motor mounts, transmission mount, control arms. Check it all.

gdavenport0701

i would have so say trans mount

Boost_Retard

my jeep was making a clunk when put into gear, greasing my slip yoke and changing u joints solved it,

DFlintstone

I'm not seeing a mount making it lurch forward. Always nice to check them though. High idle? Don't know if the kick-down cable out of adjustment could do that. Also just on GP, anything with the tranny, I'd check the fluid. Pink & clean, dark & ugly? Normally a U-Joint. And again, I don't see the "lurch", but the thunk could also be the differential.

Potatowalker

When my slip yoke was dry the jeep would clunk after I stepped on the gas from stopped and would also clunk when I came to a stop at intersections. This was without changing gears on the auto tranny. It felt like there was something loose in the rear suspension almost, but also like the tranny was doing weird stuff. Greased the slip yoke on the front of the rear driveshaft and now the loud clunk from the middle underneath is gone.

There was a bit of a lurch when shifting into D from Park after that still, but no clunks when starting or stopping. When I adjusted the "kickdown" cable a.k.a. Throttle Valve linkage cable, it shifts a lot smoother and the lurch is way less, but still there a bit. My tranny fluid was always nice and red and at a good level.

I still have a bit of a high-idle due to some electrical/sensor gremlin I've yet to conquer which I believe is why there is still a little bit of lurch when shifting out of park.

If you don't have any weird grinding or vibrations while rolling/driving I doubt it's a U-joint. Those are easy to check so I'd just put hands on them and rule that out/in for cheap. Take the driveshaft off, clean up and grease the slip yolk end and check those U-joints all at once is what I'd start with!

I was afraid it was excessive slop in my rear diff and was glad to find it wasn't! I've never dealt with a loose mount but those are always worth checking too and easy enough to do.

It may be one thing, but in my case it was/is a few things! I have 198K on the engine/tranny with no rebuilds. I hope what I've dealt with can be of help to you!

BotakBeng

I'll go with the cheapest fix first.

1)Grease Slip Yoke
2)Replace Transmission AND Motor Mounts.

jacob.

ill check every thing u said i have a bad felling its the diff my my luck .but i picked up a 8.25 29 spline for free just no spider gears so not to worried about the diff because i was going to swap in the free diff once i picked up a locker .im going to try greasing the slip yokes iv already done the u joints and all also check the tranny mounts .i do notice it revs i little high when starting and tacks a bit of time for the rev to come down. thanks for all the help

jake

DFlintstone

So it's only high after starting? Guess that's not your "lurch" then. Some idle thoughts:



Vacuum leaks suck. I go around with short little shots of starting fluid, if you hit one the sound of the engine will change. Small little shots! You don't want that stuff to accumulate. It's a fire hazard, but It evaporates right away. Also with a tube, or a section of hose you can listen for it. Don't forget the lower O rings on the injectors need to seal as well. (uppers would leak fuel).
The manifold bolts have a habit of loosening, especially that rear one. On anything like that you never want to tighten only one. It can warp/bend, even crack things. If I found that any that where easy to reach where loose, I'd pull the air cleaner and tighten them all, starting in the middle and working out towards the ends. I go over about three times. It's a bear of a spot to get a torque wrench on them all. Just don't ape on it. If its firm and not turning, no point in going on to break it, a REAL *****. The rearmost bolt underneath takes a little doing, but it can be done with the right extension. For that very back one by the firewall I use way long extensions (18"), with a swivel at the socket. Anyway, that's a good thing to check on any old Jeep.



IAC CLEANING 88


The Idle Air Control (IAC) is mounted on the back of the throttle body. The valve controls the idle speed of the engine by controlling the amount of air flowing through the air control passage. It consists of a stepper motor that moves a pintle shaped plunger in and out of the air control passage. When the valve plunger is moved in, the air control passage flows more air which raises the idle speed. When the valve plunger is moved out, the air control passage flows less air which lowers the idle speed. Over time and miles, the IAC can get carboned up which can have an adverse affect on idle quality. Cleaning the IAC may restore proper function and is an easy procedure to perform and good preventive maintenance so it is never a bad idea.

CLEANING THE JEEP 4.0 IDLE AIR CONTROL

Remove the air filter cover, associated hoses and the rubber boot that goes from the air filter cover to the throttle body. Remove the IAC with a torx driver (2 bolts; one can be kind of hard to get to)

“Gently” wiggle out the IAC from the throttle body. Gasket on the IAC can be re-used if it is not damaged

Clean the IAC with a spray can of throttle body cleaner; inexpensive and available at any place that sells auto parts. Throttle body cleaner is recommended rather than carburetor cleaner as it is less harsh, safe for throttle body coatings and is best for this task. Use cleaner, a rag and a toothbrush and or Q-Tips. Be gentle; don’t twist or pull on the pintle that protrudes from the IAC as it is fragile and you could damage it.

Thoroughly spray clean and flush where the IAC seats in the throttle body with the same spray cleaner

It is also a good idea to clean the entire throttle body itself, the butterfly valve inside of the throttle body and all associated linkage as long as you have things disassembled

Reinstall IAC and check idle quality.

ajaysarin

Appreciate all the good points to check on mine. Just got my 01 back from the shop after having a flex plate and tranny mount replaced. I am noticing it clunks going into reverse or drive. For whatever reason feels like it is idling little higher so I will check that kickdown cable see if that is an issue. I am hoping it is something simple and nothing going on with the diff, its the Chrysler 8.25.

DFlintstone

Yo bro, and welcome to the forum. You found a very old thread, you might want to start your own......driveline U joints and play in the differential are things you may want to rule out for starters. It's rare, but possible the tranny cable is holding the idle high, a vacuum leak is more likely.