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Manual Trans. Thud when shifting

wildcatgoal

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U tried the diff bushing and does not work right?
Like I've said elsewhere on this forum, the diff bushings do not reduce this noise. If anything, they'll increase it (if your car is prone to the noise). It is play within and between the transmission and differential, not the differential moving. I had a super similar (probably same) issue with a Chevy truck. Ultimately replacing the differential solved it. I was no longer able to literally, by hand, twist the drive shaft left and right a pretty significant distance and hear the exact clunk I heard in the truck. Guess what my drive shaft does? And it isn't the driveshaft itself that has play when twisted. It's what it is connected to.
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fogus

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Still following this. Still willing to organize my "thud day" in the North East USA where we hit a dealer with 5+ reports in a single day so they freak out and do some investigation :)

daltron, I'd love to hear how your test went.

We should probably summarize all the "fixes" everyone has used and had success with at some point.
 

Genxer

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Like I've said elsewhere on this forum, the diff bushings do not reduce this noise. If anything, they'll increase it (if your car is prone to the noise). It is play within and between the transmission and differential, not the differential moving. I had a super similar (probably same) issue with a Chevy truck. Ultimately replacing the differential solved it. I was no longer able to literally, by hand, twist the drive shaft left and right a pretty significant distance and hear the exact clunk I heard in the truck. Guess what my drive shaft does? And it isn't the driveshaft itself that has play when twisted. It's what it is connected to.
It may be that our diffs have a fair amount of gear lash. I would interested to see if anyone has compared clearances on their gears to factory specs. Or, do these Torsen diffs have a looser spec?

The main reason I did the diff bushings was for more stability and it did that for me. Tightened things up a bit.
 

daltron

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Still following this. Still willing to organize my "thud day" in the North East USA where we hit a dealer with 5+ reports in a single day so they freak out and do some investigation :)

daltron, I'd love to hear how your test went.

We should probably summarize all the "fixes" everyone has used and had success with at some point.
My thud is now gone. I can only assume it was the driveshaft.

These are all my drivetrain related mods/fluids. The nice thing is that they were all done over time so I definitely think it was the driveshaft. What I bolded is what was the last install, with what I assume fixed it was the driveshaft. I have a PP with the stock 3.73 rear end with the Torsen.

Steeda Tri-Ax
DSS Aluminum Driveshaft
UPR Driveshaft Safety Loop

McLeod RXT
McLeod Steel Flywheel
DSS 1400HP Halfshafts
RP Synchromax
AMSOIL Severe Gear 75W-90
Steeda IRS Subframe Bushings
Steeda IRS Subframe Alignment kit
Steeda Differential Race Aluminum Bushings
 

EXP Jawa

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It may be that our diffs have a fair amount of gear lash. I would interested to see if anyone has compared clearances on their gears to factory specs. Or, do these Torsen diffs have a looser spec?
I pointed this out a while back, but it bears repeating. The Torsen internal gearing lash is actually quite good, but the lack of a preload spring (which a clutch diff needs to load the clutch) means that the lash it does have isn't masked like it is in a clutch diff.

Also, by checking lash at the pinion, what you feel is the diff lash, multiplied by the gear ratio, plus the r&p lash. So, when you have a 3.73:1 gear set versus 3.31 or 3.55, the apparent lash is amplified more.

And of course, the 3.73 gears and the Torsen are bundled together on these cars. So, combined together it makes it seem even worse.
 

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Rustang

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So are there 6MT's out there that dont have the thud?
When i bought my car I knew about the problem and all 3 of the GT PP's the dealer had on the lot had the thudding.
Right here, no thud whatsoever. I have heard one with the thud too so I know what it sounds like.
 

duke107628

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So I got back from the dealer. No issue were found regarding the thud noise
 

luv2spedup

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So I got back from the dealer. No issue were found regarding the thud noise
The dealer told me the same thing that the Thud and the driveline noise is normal for MT82... Since it's still under warranty let's how it goes..
 

duke107628

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The dealer told me the same thing that the Thud and the driveline noise is normal for MT82... Since it's still under warranty let's how it goes..
I am going to get the diff bushing and see how it goes
 

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duke107628

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Oh, I love mine. Just didn't want someone to have to go out and get it to specifically fix this problem. It's a great mod!
Yep. I agree with you on this one. Going to eliminate some wheel hop and hoping will reduce the thud
 

camobob

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It may be that our diffs have a fair amount of gear lash. I would interested to see if anyone has compared clearances on their gears to factory specs. Or, do these Torsen diffs have a looser spec?

The main reason I did the diff bushings was for more stability and it did that for me. Tightened things up a bit.
Dealer checked mine against spec and said I had 75% of the the max allowable lash. They don't deny the thud or that it is unusual for most cars. They just said it's normal for this particular car - no problem here....
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