42RLE clicking

DropTopDon

TJ Enthusiast
Joined
Nov 7, 2019
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642
Location
VA

Recently started hearing this clunking noise when shifting my 42rle into drive or reverse. I can’t tell if i’m being paranoid (236k miles stock tranny) or if I need to do something about it. I can sometimes feel the clunk and it jolts the jeep a little bit. It didn’t ever do this before atleast that I can remember. I have had the jeep for about 4-5 years and haven’t done a transmission fluid change because I was told not to so I’m not sure the condition of the fluid though it looks pretty red on the dipstick.

I checked the transmission fluid but I wasn’t sure if I was supposed to wipe the dipstick and reinsert like you do with the engine oil so here are pictures of both.
D7E783AC-1AC8-4C93-9624-63708F462287.jpeg

This is before re inserting^



E1A4DCFF-023C-4B83-B828-C215D391466F.jpeg

this is after^
 
I can't tell what it's indicating in either photo. First, make sure the engine is running while you check the ATF level with the dipstick.

Yours might look a little more brown and less red than it is ideally but how is the level? With the engine warm and running, the ATF level should be, absolutely, all the way to the full line. If it's not add enough ATF+4 (nothing else) in through the dipstick tube (use a funnel) until it is Full. It's better for an automatic transmission to be slightly overfilled than slightly underfilled.
 
I can't tell what it's indicating in either photo. First, make sure the engine is running while you check the ATF level with the dipstick.

Yours might look a little more brown and less red than it is ideally but how is the level? With the engine warm and running, the ATF level should be, absolutely, all the way to the full line. If it's not add enough ATF+4 (nothing else) in through the dipstick tube (use a funnel) until it is Full. It's better for an automatic transmission to be slightly overfilled than slightly underfilled.
I checked when the engine was running. Mine seems to be in the middle of Hot and Cold. I’ll add some atf +4 and see if it helps
 
You can't judge much by the color of the fluid. It says that clearly in the factory service manual. At a minimum change the transmission filter when you have a chance, it is required maintenance for that transmission just like changing the spark plugs or air filter.
 
Added fluid and the clunking remained. Took the front driveshaft out too just for kicks and that wasn't the culprit either. The clunk does not sound as bad in the video as it does in real life. Any suggestions on what it may be? It only happens when going from P to R and D on occasion, not every time that I shift into them. I read in a similar thread it may be a valve body issue?
 
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The valve body is normally more of a tick-tick-tick noise and not a clank but I've never heard a bad one. I think the u-joint suggestion made by @onoffroad is a good one, it's easy to check the rear driveshaft. You can always have somebody do a mild brake stand in forward and reverse with the hood up and see how much the engine dances around if you suspect motor mounts.
 
Noticed that the clunking happens when I am just cruising too not just when shifting into gear. I'll give those a check and report back when I get a chance thank you!
 
I jacked up the rear and no lateral play in u-joint closest to TC. VERY minimal to no movement In the furthest back U-joint though which is where I suspect the noise to be coming from.

You can see in this Video what I am talking about.

I had my brother shift into P, D and R. Is the rear driveshaft supposed to move like that every time? As for the noise, if not my U-Joint would it be possible something in my rear diff could be making the noise or is it safe to say it is the U-Joint?
 
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Anyone have any input? Also I had someone tell me it looks like an “accumulation of lash”.
 
Anyone have any input? Also I had someone tell me it looks like an “accumulation of lash”.
Accumulation of lash is normal. You have so many thousandths lash between the gears/chain in the t/case, between the output shaft and the slip yoke, and between the gears in the rear end. As you put the thing in gear, the driveshaft rotates to take up all this slack. When you shift from drive to reverse, it rotates the other way and takes up the slack again. This can give you a clunk when you first put it into gear, and a minor clunk is normal.
Of course, if something goes wrong (bad u-joint, bearings or gears in the diff, something internal to the t/case) this can get real bad.
You can test this lash by setting the parking brake, taking the trans out of gear, and manually turning the driveshaft back and forth. Movement of the driveshaft should probably be somewhat under 1/4" back and forth. If it's much more than that, you might have a problem somewhere.
 
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Looks like I found the issue. Odd bc there was no play in the joint until I disconnected the rear driveshaft from the jeep. No clue how this even happened
E8049EEF-188C-429B-B8F8-776721B4AE8A.jpeg
 
Looks like I found the issue. Odd bc there was no play in the joint until I disconnected the rear driveshaft from the jeep. No clue how this even happened
View attachment 322369

Hey what was the problem? I’m having this exact same problem with my jeep as well when I’m in reverse backing up then go to drive CLUNK it sounds nasty exactly how urs did and I went on a bunch of forms no one was giving me a real response to my problem but it looks like you figured it out what was going on with it please help me out 🙏🙏
 
Hey what was the problem? I’m having this exact same problem with my jeep as well when I’m in reverse backing up then go to drive CLUNK it sounds nasty exactly how urs did and I went on a bunch of forms no one was giving me a real response to my problem but it looks like you figured it out what was going on with it please help me out 🙏🙏

For me it was a worn out u joint in the rear driveshaft. Likely the culprit for you too