View Full Version : THUD! After acceleration?

12-18-2014, 02:15 PM
//Edited for hopefully a better description (The quick pump of brakes description is the best I can think of for the lurch when you release the pedal)

Hey guys, I have a 2001 B5 with the 5 speed manual in it. So I went out and drove my car around a bit since its been sitting all week, and I noticed a lurching* feeling after acceleration and I release the gas pedal. Lower RPMs its not there, but its really noticeable when I'm going out onto a street and getting up into gear and for instance I'm in the top of Third and I release the pedal to coast a bit. When I let off the gas, the car sort or lurches forward and theres a thud which I presume is coming from my transmission. Any idea what this is?

Thanks guys

*Lurching as in the car was accelerating, I release the pedal and the car lurches (er rather makes me lurch forward) as if I pumped the brakes real quick..

12-18-2014, 02:44 PM
Sounds like a bad mount. Engine, transmission, differential, anyone of those.


12-18-2014, 02:56 PM
Geesh! Well mine definitely doesn't do that. It idles perfectly fine and I revved it up, no noise or lurching as seen in that video. Just happens when I'm in gear driving and I let off the pedal after accelerating. It seems to be related to the amount of torque. (Lower gear it doesnt take higher RPMs to do it, but higher gears it requires the higher RPMs) At least I think that correlation is a legit one to make? Either way, I still don't know how to interpret it. My dad says he thinks its possible bearings out on the main shaft in the transmission. Not sure if related buy my dad thinks it is. When I get on it and let off the pedal, my gear shift moves. He said he thinks my transmission has pretty much no linkage and the shifter feeds straight into the transmission, hence this slop in the shifter?

Idk, is any of this making sense to anyone that can possibly point me into the right direction? I just bought the car a month ago, we're now looking into buying another transmission to have rebuilt and put in. A guide or thread link about transmission compatibility with the codes and so on would be appreciated.

Thanks for reading all that.

// Should also include that its a Quattro

Mad Cow
12-18-2014, 03:06 PM
Your transmission's probably fine, our 5spds are really tough. The shift linkage moving is normal, you can fix it by lubing the shifter slider rails on either side. If you pop off the shifter trim and boot you'll see what I'm talking about. I'd inspect the motor and transmission mounts, possibly the rear diff mounts too. It could also be a bad cv joint in the driveshaft or an axle, it seems to be pretty uncommon but it happened to my car.

12-18-2014, 03:22 PM
Could the CV joint or mounts really cause the lurch when I let off the accelerator? I mean I believe you and I'd be more than happy to replace it versus a transmission, but I'm just trying to get it in my mind physically whats going on down there to cause it.

//I should revise my previous statement which may effect the diagnosis so far. It doesn't lurch FORWARD, but rather.. backwards? The car suddenly deaccelerates.. if that makes sense?

Mad Cow
12-18-2014, 03:33 PM
I don't really understand what you're describing, so my suggestions are just general driveline thud suggestions. A video would help.

12-18-2014, 03:45 PM
I don't really understand what you're describing, so my suggestions are just general driveline thud suggestions. A video would help.

Yea sorry I'm bad at describing things through text haha. I'm honestly going to put it out of mind for the moment. I have one more final exam to go tmw evening that I'm going to focus on, then Saturday morning I'm going to drive about 100miles to my dads for my Winter break, once I'm up there I can get it up on stands and take a look at whats going on. I'll let you know if I find anything out, or I may be back with more questions! Thanks for the help.

12-18-2014, 09:14 PM
bump for the new description to help tell whats going on.

12-19-2014, 01:55 AM
So you feel noticeable drag when off throttle and a sudden "punch in the face" from the driveline?

12-19-2014, 08:12 AM
Yes, a drag. But it'd not all the time just for s short period after accelerating and then letting off

12-19-2014, 09:15 AM
I'd reckon slack in the driveline then. Mostly in trans/rear diff mounts. Mine does the same thing, so there's nothing to worry about. Rear diff carrier mounts rarely, if ever, go bad.

12-19-2014, 09:45 AM
Ok, I got a chance earlier this morning to head out on the highway and get up into fourth and fifth. In fourth I could notice a slight bump when getting on the throttle, which makes me lean more and more in saying you guys are right about the mounts. Its probably getting torqued down there and moving that inch of travel or so in the bad mount. I just have to drive it 100 miles tomorrow and then I can get it up on stands and take a better look. Thanks Bordom.

EDIT: My main concern still stands though that this slop is coming from inside the Tranny, but idk.. as I said, ill check it all out tmw and post and update on here about what I find.

12-19-2014, 03:33 PM

12-20-2014, 05:31 PM
Well. After consulting with my dad who is a diesel mechanic and a car enthusiast himself. He said its really nothing to worry about. Its wear and tear to be expected from a car its age and mileage. So. Thanks for everyone's input and trying to help me out!