Excessive front shaft play compared to rear causing thuds when accel/decel, gear changes.

[Crazy Dragon]

Shafts are in perfect condition. Greased and no play on u-joints. So it's nothing to do with the official clunk thread.

Symptoms:
1. While coasting, if I let of the accel pedal, it clunks, and when I press the accel again it clunks.
2. Under light acceleration, shifting from 2-3 there's a HEAVY thud. But if under hard acceleration it shifts smoothly.
3. Similarly, if braking to a stop, the shift from 2-1 gives another similar thud, but softer thud than symptom 2.
4. Centre Diff Lock engaged: Completely removes ALL clunks or thuds.

Shifting from D-R , R-D, the rear drive shaft turns less than the front drive shaft. My mechanic mentioned that the rear play looked normal, but the front is turning twice the amount the rear is turning when shifting in between D-R or R-D.

Things that I've done so far:
- Replace front CVs and drive flanges (still has a bit of play but mechanic is saying that that's normal).
- Changed front, rear and transfer case oils. (None of the diffs whine or have any fragments or shavings present during oil change).
- Refurbished A442F installed.

What else can I look at? Is it normal that my front shaft has twice the amount of play compared to my rear?

 

[Crazy Dragon]

I've searched through the forum multiple times using different keywords and the only similar symptom I could find is from this post. It's exactly my problem but unfortunately it went dead 5 years ago without any solutions.

Clunk from drive line / transfer case (NOT "The Clunk" from rear prop shaft)

 

[aging fleet]

edit, just noticed you already addressed the CVs and drive flanges.

 

[2001LC]

Have you lubed the aft & forward propeller shafts (AKA drive shaft) slide yokes and spider joints! Your issue sound like you've not been lubing every 5K miles..

Should be near 0 detectable play between NEW OEM hub flange (drive flange) and front drive shaft (CV).


Excessive play from worn hub flange and front drive shaft teeth.

 

[2001LC]

Other common area of clunk is front differential bushing get worn out.
This is a video of front bushing and puck, there is also a side and rear. They get old move excessively, but should move some..

 

[Crazy Dragon]

Other common area of clunk is front differential bushing get worn out.
This is a video of front bushing and puck, there is also a side and rear. They get old move excessively, but should move some..

Yeap the whole driveshaft, slide yokes and spider joint/u-joint has been lubed. Pumped them full of grease until they start pushing out old grease as recommended by the official clunk thread.

I think I will try the bushings next.

This isn't just a normal light clunk. It's actually a huge bang/thud. It happens when shifting of gears. But I'm 100% sure it wasn't the transmission as it got replaced with a fully rebuilt one.

Could it be my transfer case/centre diff or front diff? What boggles me is that the oils were in great condition when I changed it. No fragments just very little metal paste which I believed is normal.

Is the front drive shaft supposed to have more play compared to the rear?

 

[2001LC]

Not really one shaft more than other, but they both have some play. Other places to look are control arm bushings. Some have report good results replacing those, when shot.

 

[suprarx7nut]

I have a very similar issue, but perhaps less extreme. I was expecting to see slop like @2001LC shows in his videos, but I didn't see any at all. I installed a new companion flange at the front diff and the issue persists. I have a TON of rotation at the front drive shaft going into the front diff. The shafts coming out of the diff have zero play at all. My slop seems to be entirely within the diff and it's output flanges.

Let us know what you find out!

 

[2001LC]

I have a very similar issue, but perhaps less extreme. I was expecting to see slop like @2001LC shows in his videos, but I didn't see any at all. I installed a new companion flange at the front diff and the issue persists. I have a TON of rotation at the front drive shaft going into the front diff. The shafts coming out of the diff have zero play at all. My slop seems to be entirely within the diff and it's output flanges.

Let us know what you find out!

Have you ever pulled the front drive shafts (CVs) and inspected the teeth of axle and in the diff.?

 

[suprarx7nut]

Have you ever pulled the front drive shafts (CVs) and inspected the teeth of axle and in the diff.?

I pulled the CVs when I pulled the diff recently, but never inspected the diff-side teeth. I was too focused on getting the darn seals swapped out, unfortunately.

The CVs looked fine, but I know it's a subtle difference between worn teeth and fresh ones without a nice reference on hand. It's live-able for now, but I'll make sure to inspect more closely if I pull the CVs for any reason in the future.

 

[vishmuzty]

Those are the EXACT symptoms that I solved by replacing the front diff bushing. As the rubber degrades and compresses, the aluminum bushing bracket / diff cover is able to contact the crossmember producing a "BANG" noise whenever the drivetrain transitions during torque load reversal (ex: off-throttle coast -> on throttle, D->R). Locking the center diff must smooth out the torque transfer so the diff doesn't load as abruptly. Either use a video camera or a helper in the driver's seat to watch the front diff bushing during P->R->N->D shifts. You will be able to stop the noise by wedging a piece of rubber between the bracket & crossmember.

 

[Crazy Dragon]

Those are the EXACT symptoms that I solved by replacing the front diff bushing. As the rubber degrades and compresses, the aluminum bushing bracket / diff cover is able to contact the crossmember producing a "BANG" noise whenever the drivetrain transitions during torque load reversal (ex: off-throttle coast -> on throttle, D->R). Locking the center diff must smooth out the torque transfer so the diff doesn't load as abruptly. Either use a video camera or a helper in the driver's seat to watch the front diff bushing during P->R->N->D shifts. You will be able to stop the noise by wedging a piece of rubber between the bracket & crossmember.

Yeah I think my next step would be to change out the bushings although they don't look that bad. But who knows since it's already 20 years old. Better than go straight to pulling the transfer case apart.

 

[Crazy Dragon]

Welp after changing all the front diff mounts, exactly NO CHANGE. Still thumping during gear shifts and acceleration/deceleration. I give up. I doubt I'd ever find a solution to this. @vishmuzty you're so lucky that solved yours.

 

[2001LC]

How do the rear end bushing (control arms) look?

 

[vishmuzty]

Sorry to get your hopes up Crazy Dragon, keep at it. I too also replaced rear control arm bushings prior to the diff bushings. While I didn’t do it with the intention to resolve the drivetrain clunking, perhaps it had some effect. My diff was clearly bouncing around the front mount so it was an obvious issue.

A GoPro camera is a very useful tool to diagnose the clunking... watch the rear & front control arms, front diff and CV shafts during clunking.

 

[Crazy Dragon]

Nah it's okay @vishmuzty . I already had a feeling it wasn't gonna do anything but it was worth a try. Just frustrating as not many people have the same symptoms but they all solved it by replacing all the front diff mounts.

But at least I've eliminated that option so now I'm 99.9% sure it's the excess backlash/play of front diff and transfer case. From P to D or R, the front drive shaft turns 2.5 times more than the rear drive shaft. That can't be normal can it? Cause I can see how CDL completely eliminates the thumps as it ensures equal torque and turns between front and rear shafts.

At the moment I'm going to leave it as I don't feel like spending much more money on it, but for education purposes, lets keep the discussion going. What do you guys reckon about the unequal amount of play between front and rear shafts?

 

[2001LC]

You say 2 1/2 time more play. But more of what 1/8", 1/2" ...?

I went and checked the play on one I've on jackstands now, so wheels free. I drew a line on aft propeller shaft and T-case, the took up play and marked a second line. I get ~3/8" (eyballed) on rear propeller shaft between the lines. Then repeated on forward PS, and got even less play.

I may be pulling frt diff. If I do I'll measure again to see if I get more.

BTW: it's a 00LX with over 350K miles.

 

[Crazy Dragon]

I don't have exact measurements but eyeballing I'd say I have about 1cm free play for rear shaft and about 3cm or more play on front shaft. This isn't free wheel, but putting R>D>R with engine on. I'd say the turn on the front shaft is definitely more than 3cm.

Mine is a 99 1HD-FTE with 385k kms.

 

[GVegasG]

Any updates as it seems like my 04 LC (302k) has similar problem. I did noticed front propeller shaft play being more than rear when turning by hand when car was Neutral both shifters. I will do more measurements and compare to another 04 (176 k) which does not have the problem.
I have greased the shafts and don’t really want to disassemble but I am curious if splines are greased properly. I will try to grease again with a different grease then red high temp bearing grease and make sure it does go thru seals. This clunk or thud is definitely different than regular clunk when putting to D as this is happening when stopping or accelerating but not all the time. I can reproduce easily even during freeway speeds.

 

[GVegasG]

I was finally able to take some videos.
Car #1 04 LC 303k miles
Rear shaft play

Front shaft play two videos


04 white front shaft play vid #2 - https://youtu.be/9_flqYUO0rU?si=EF8127XXWKjisBfZ


Car #2 04 LC with 170k no clunk
Front shaft play
04 tan front shaft play - https://youtube.com/shorts/6eF-xDzb88w?si=0OGRr_zftBY1jmMy
It is obvious that car #1 has more play in the front propeller shaft. I think now the question is if the problem is cv/flunge combo or something with front diff.