Loud "THUMP"

**1badtk** · 07-05-2007, 06:11 AM

98 Z28

Shift from R to D there is a loud thump. Sounds like the tranny is jumping up, transmission mount is solid, rubber mount looks good. Someone suggested a trailing arm bushing on top of the transmission at the tail shaft area. ???

**bigrondownhiller** · 07-05-2007, 10:52 AM

do you feel the thump or just hear it? could be u joints or a bad ring and pinion.

**sic2001** · 07-05-2007, 01:33 PM

wheres the u joints and ring and pinion? Is that from the drive shaft to the diff ring/seal?I have the same problem but mine thumps at slow downs and slow take offs as well.

**bigrondownhiller** · 07-05-2007, 01:38 PM

the u joints are at either end of the driveshaft. usually the rear one goes first. the ring and pinion are inside of the differential.

**1badtk** · 07-05-2007, 06:00 PM

Originally Posted by bigrondownhiller

do you feel the thump or just hear it? could be u joints or a bad ring and pinion.

I can feel it in the floor, its not u-joints, already checked the drive line.

**sic2001** · 07-05-2007, 06:36 PM

have you checked the torque arm bushing?
I replaced mine chasing this thump of ours, especially since you can feel yours in the floor

**mglangley21** · 07-05-2007, 08:43 PM

Have u took the transmission mount off to see if it has cracked or ripped away any at all, because my ss had a thump but u could not see it with out pulling it off!! And it was the trans mount!

**1badtk** · 07-06-2007, 05:04 AM

Can I just buy the bushing, or do I replace the complete torque arm? Is it a oem item only or available form the autoparts stores?

**Wesman** · 07-06-2007, 12:40 PM

Originally Posted by 1badtk

Can I just buy the bushing, or do I replace the complete torque arm? Is it a oem item only or available form the autoparts stores?

You can buy just the bushing.

Speed Inc has them for $13.99, and they are made from polyurethane.

Don't waste your time going to the auto parts store, doubt anyone will have it, and if they do it will only be a cheap rubber one anyway.

**1badtk** · 07-06-2007, 03:01 PM

Thank you

**2000TransAm400HP** · 07-07-2007, 08:12 PM

When you shift from Reverse to Drive you hear a thump? Is that sound when it is trying to go into gear. Another words if you had it in Reverse and put it in drive and gave it some gas as it was being shifted into drive would you hear the thump and then have the car jump forward as it engages? It sounds like that automatic transmission might be showing early signs of slipping when changing gears.

**1badtk** · 07-09-2007, 03:38 AM

Well I looked at the tranny mount and torque arm mount, both are ok. The sound is coming from the right rear area, and I noticed the car is sitting 1" lower on the right side. Going to look at the shock mounts and shocks next.

**sic2001** · 07-09-2007, 11:49 AM

LOL I have the same uneven drop as well as a few others. You figure that one out and you win a nice prize...or a heart felt thank you hahahah

**TX_WS6_02** · 07-09-2007, 12:09 PM

Originally Posted by 1badtk

Well I looked at the tranny mount and torque arm mount, both are ok. The sound is coming from the right rear area, and I noticed the car is sitting 1" lower on the right side. Going to look at the shock mounts and shocks next.

Right before my rear went out...i experienced that THUMP. It made my center console jump. Felt like someone took a sledgehammer to the underneath of my car...they said that the bearings went out. Hope whatever you find out isn't gonna cost you out the wahzoo

**2000TransAm400HP** · 07-09-2007, 12:18 PM

YOu are hearing this sound when you shift from Reverse to Drive only? Everyone is pointing away from the tranny. I thought tranny because your problem seemed to be happening when you shifted so I must have misunderstood your problem. If you are having a problem in your rear differential somewhere then thats another story. Is everything stock under your car? make sure the exhaust isnt hitting the crossmembers. That can give you a thump sound. Actually this one should be really easy to fix. You should take a quick peek underneath your car and feel around everywhere to make sure everything is nice and tight. If its coming from your rear however then it sounds like something in your differential..... Make sure your driveshaft and yolk are all good and tight.

Originally Posted by 1badtk

98 Z28

Shift from R to D there is a loud thump. Sounds like the tranny is jumping up, transmission mount is solid, rubber mount looks good. Someone suggested a trailing arm bushing on top of the transmission at the tail shaft area. ???