Driveline "Clunk" after H55 swap (3 Viewers)

[KOB ONE]

Any thoughts or advice appreciated on this issue.

I finally finished swapping out my A440 for an H55F (behind a 12HT). I’ll try and get around to posting some photos / thoughts on the trans and t-case rebuild and swap at some point, although those topics have been quite well covered here in other threads. After a few short test drives, I’ve noticed a SIGNIFICANT “clunk” / “thud” from the driveline, most noticeable when shifting into 4th or 5th or when suddenly accelerating or decelerating in either of those gears. I believe the same is present in 1st-3rd, but less noticeable.

A few details:
Using drive-shafts from a doner vehicle where I sourced the H55, they’re not in great shape, but the u-joints didn’t seem to have any obvious play in them or anything before installation

• Vehicle has an OME lift from a previous owner (I think 2.5”, maybe 3”) – clearly some of the driveline geometry was changed when it was lifted.
• Rear pinion angle is all wrong (flange is tilted up about 7 degrees). The t-case output flange is close to 90 degrees (maybe 1 degree down) … so at least 6-7 degrees off the pinon angle. I’m sure this is way too much; however, this wasn’t an issue before the trans swap, which is why I’m scratching my head now.

My leading theories:

• Was the issue always there, but masked by the “cushion” of the automatic and torque converter? If so, still need to figure out the problem.
• OR, the longer driveshaft behind the H55 has changed the drive-shaft geometry enough that now the screwy pinion angle is causing the issue (although I’m not sure it would contribute to this very loud and specific “clunk” noise
• Or something wrong with the rear diff (not my area of expertise at all), allowing too much play and allowing for some “crashing” of driveline components more noticeable in higher gears

I’m hoping that someone has had a similar experience and can offer some advice. In an ideal world I’ll shim the rear axle to get the pinion angle correct, but unless someone can correct me, I’m not confident that’s the issue (though I’ll end up doing this job regardless).

If you’ve read this far – thanks in advance for any thoughts.

 

[mcmlxxxv]

not sure diff angle is the cause ... even 7degree. you would get vibrations before a clunk sound.

Are you sure its not from the transmission ? 4th gear is direct drive and 5th gear is on the end of the counter shaft loose transmission bearing could cause a clunk or too much backlash in the rear differential.

I doubt your problem can be the output gear in the Transfer case , but mine was having a very worn out bushing causing a lot of noise.

 

[KOB ONE]

not sure diff angle is the cause ... even 7degree. you would get vibrations before a clunk sound.

Are you sure its not from the transmission ? 4th gear is direct drive and 5th gear is on the end of the counter shaft loose transmission bearing could cause a clunk or too much backlash in the rear differential.

I doubt your problem can be the output gear in the Transfer case , but mine was having a very worn out bushing causing a lot of noise.

Thanks for your reply mcmixxxv. I tend to agree about the diff angle, I'm not getting the vibrations you'd think I'd get... but I was hoping some shims for the rear axle might be an easy solve. My fear is I messed something up when I rebuilt the trans / transfer case. I don't have the willpower to pull the trans apart again. I'll try shimming the rear axle first, and look at the diff after that. If or when I solve this I'll report back.

 

[mcmlxxxv]

Thanks for your reply mcmixxxv. I tend to agree about the diff angle, I'm not getting the vibrations you'd think I'd get... but I was hoping some shims for the rear axle might be an easy solve. My fear is I messed something up when I rebuilt the trans / transfer case. I don't have the willpower to pull the trans apart again. I'll try shimming the rear axle first, and look at the diff after that. If or when I solve this I'll report back.

Try have a friend (a thrustworthy one...) to play with the clutch with your hands on the t-case see if you feel any knock ?

try doing than with parking brake on engine runing , that might track the noise.

 

[KOB ONE]

Try have a friend (a thrustworthy one...) to play with the clutch with your hands on the t-case see if you feel any knock ?

try doing than with parking brake on engine runing , that might track the noise.

Hmmm. I have the carpet and trans tunnel cover off right now. Maybe I could do what you're suggesting by just reaching down to the t-case with my right hand and feathering out the clutch....

 

[GLTHFJ60]

Did you rebuild your A440 transfer case onto the H55? Did you happen to take any pictures of the inner splines of the transfer case input gear?