Thud Sound when hard downshift or Full Power up shift

[2002_Viper_GTS_ACR]

I noticed at the track about about 2 weeks ago, that when I would down shift to reduce speed in a braking zone, I would get a hard THUD sound in the rear. So I stopped down shifting, relied heaver on my brakes and made it through the weekend with no issues.

I told myself I'd fix it the following weekend. So I tried. I went through and retorqued all relivant things, like shock mounts, wheel hubs, A Arms and differential mounts. I figured that would take care of it. But then I noticed it happened again, when I "got onto the car" the other day, and was doing a sort of zero to 60 as quick as possible type of driving, and when I went into second, THUD sound came back.. like my chassis in the back was quickly whacked with a ball peen hammer. So obviously I backed of again.. and took another look when I got home.

I cant find anything wrong. I checked the differential mounts, the tranny mounts, the 1/2 shafts, and the universal joints in the drive shaft.

ANY IDEA, whats causing this? The thought of taking it to the dealership and saying, oh can you fix this, it only happened when you really romp on the car.. scares me, because that means the technician is going to be out on the street beating on my car

Help please !!

 

[Finally got it !]

I noticed at the track about about 2 weeks ago, that when I would down shift to reduce speed in a braking zone, I would get a had THUD sound in the rear. So I stopped down shifting, relied heaver on my brakes and made it through the weekend with no issues.

I told myself I'd fix it the following weekend. So I tried. I went through and retorqued all relivant things, like shock mounts, wheel hubs, A Arms and differential mounts. I figured that would take care of it. But then I noticed it happened again, when I "got onto the car" the other day, and was doing a sort of zero to 60 as quick as possible type of driving, and when I went into second, THUD sound came.. like my chassis was being jacked with a ball peen hammer. So obviously I backed of again.. and took another look when I got home.

I cant find anything wrong. I checked the differential mounts, the tranny mounts, the 1/2 shafts, and the universal joints in the drive shaft.

ANY IDEA, whats causing this? The thought of taking it to the dealership and saying, oh can you fix this, it only happened when you really romp on the car.. scares me, because that means the technician is going to be out on the street beating on my car

Help please !!

My thoughts would have been with the 1/2 shafts. Did you take the weight of the suspension when checking for loose parts???

 

[dave6666]

Transmissions - the Tremec T-56 - make noises. Mine does it all the time when using the clutch. Not from the rear area of the car though, close to where the seating area is. I've seen plenty of posts about it, and ignore it, or better yet, turn that Alpine up.

 

[Hamrhead]

Do you know anyone with a Viper that you can 'compare' noises with?

Wish ya lived closer...

 

[2002_Viper_GTS_ACR]

Ist, yes, certainly took the weight off the car when I checked the suspension, actually had all four courners up on jack stands at the lift points.

Also, 13k miles and it never "thudded" before, so it cant just be the tremec, or I would have heard it before. Also would have heard it in the gen 2 I had, or my dads 2005 Viper with 34k on it.

No something is wrong, I just dont know where. And the 1/2 shafts in a gen 3, are actually CV's.. so not too much to check.. its all sealed

Hammer, yes my Dads, which I always drive when I fly home. So I know this isnt normal. Something is broken or getting ready to break. Any ideas, anyone else have a similar issue?

Anyone?

Thanks,
Jon

 

[Hamrhead]

If you can consistently recreate that noise when you downshift, that's what I'd tell the dealer.

I understand what you mentioned about the Tech drilling on your car, and it *****, but that's what the warranty is for! Let him go out and downshift the car until he finds the problem. IMHO.

 

[Andrew/USPWR]

Do you have a fifth of jack rolling around in the back

Don't offended but, I assume your "heel and toeing" on your down shifts. Otherwise the halfshafts and dif. can take a beating.

 

[jpas]

I noticed at the track about about 2 weeks ago, that when I would down shift to reduce speed in a braking zone, I would get a hard THUD sound in the rear. So I stopped down shifting, relied heaver on my brakes and made it through the weekend with no issues.

I told myself I'd fix it the following weekend. So I tried. I went through and retorqued all relivant things, like shock mounts, wheel hubs, A Arms and differential mounts. I figured that would take care of it. But then I noticed it happened again, when I "got onto the car" the other day, and was doing a sort of zero to 60 as quick as possible type of driving, and when I went into second, THUD sound came back.. like my chassis in the back was quickly whacked with a ball peen hammer. So obviously I backed of again.. and took another look when I got home.

I cant find anything wrong. I checked the differential mounts, the tranny mounts, the 1/2 shafts, and the universal joints in the drive shaft.

ANY IDEA, whats causing this? The thought of taking it to the dealership and saying, oh can you fix this, it only happened when you really romp on the car.. scares me, because that means the technician is going to be out on the street beating on my car

Help please !!

It is actually your rear diff housing moving. Check the mounts and bolts, but hard shifting (up or down) will cause the diff to bang around.

 

[Finally got it !]

It is actually your rear diff housing moving. Check the mounts and bolts, but hard shifting (up or down) will cause the diff to bang around.

I could buy that. Sounds very plausible....

 

[2002_Viper_GTS_ACR]

hey Jpas... Thats what im saying.. I thougth the same thing, so I torqued all the bolts holding the diff (4) and it still does it

Jon

 

[EllowViper]

My '01 did it and it was a combination of the soft motor mounts and trans mount flexing under hard accel/decel. The top of the trans/shifter housing was banging against the tunnel. My $.02

 

[Nader]

Sometimes when coasting in gear and get back on the gas, i get a clank from the rear.

Sound similar?

 

[2002_Viper_GTS_ACR]

Sometimes when coasting in gear and get back on the gas, i get a clank from the rear.

Sound similar?

Nope thats the standard "back lash" that exists in our diffs. Completely normal, and well used to it, this is a much louder thud. However, I tried to make it happen again last night, and couldnt. I didnt go crazy.. just tried it 1 time, and the rocketed up to 60 mph without doing it. I think it i take her 95% she wont do it.. if I do 100% balls out she would.

Jon