Quattro Driveline issue

[davkav]

Hi lads,

I haven't been on here in a good while, looks like I will be around for a bit longer now as I am not in the BMW anymore. I never did sell the A4 in the end its back as my daily now.

I have a small issue I'm hoping some of you quattro drive line experts can help me with.

Recently I was realigning my sub frame but the bolts didnt tighten fully as they are one time use only. It took 3 weeks for Audi to get the bolts in for me but during that time I didn't have another car to drive so continued to drive it.

The subframe is fitted with new bolts now and doesn't move at all. Once I got it back out on the road though I noticed there was a thump from the rear end everytime I pulled off, changed gear or simply came on and off the accelerator pedal. Presumably this was down to the front subframe allowing the engine to shunt the whole rear end much like an impact gun.

I thought it was the rear diff hanger but I cannot see any excess movement from it when I have the car on a ramp.

I did notice however that my prop-shaft can move nearly 10* before it engages the rear diff. I have attached a link to a video I made of what I am seeing.

In addition to this I notice a few degrees of play between the two sections of the prop-shaft as well, is this normal?

I could be looking in the wrong area altogether, it may just be the diff mount or rear subframe bushings.

Would you mind having a look at the video and letting my know your thoughts?

Thanks,
Dave

https://drive.google.com/file/d/0Byz...ew?usp=sharing

[cschuster]

That just looks like gear backlash to me. If you only touched the front sub frame, and the noise is coming from the rear, than its probably your rear diff mount. Check that out first.

[davkav]

I presume the same but it just looks a bit excessive...

[SJorge3442]

I havent played with my driveshaft in a while, but I wanna say thats normal. I'd wait until someone else can chime in, but I believe that is normal.

[walky_talky20]

I think that amount of backlash is a bit excessive, and that quattro Audi's normally have excessive backlash on the rear diffs when they get some miles on them. So I think it's both normal and excessive at the same time.

I actually swapped the rear diff on my car around 200k to one with half the miles. It felt somewhat better and got rid of some "clanking" I had coming from the diff, especially when dropping the clutch in Reverse. I plan to open my old diff and actually measure the backlash at some point, then set the backlash on the *tight* side of *tight*, reinstall and see how that goes.

[davkav]

I think that amount of backlash is a bit excessive, and that quattro Audi's normally have excessive backlash on the rear diffs when they get some miles on them. So I think it's both normal and excessive at the same time.

I actually swapped the rear diff on my car around 200k to one with half the miles. It felt somewhat better and got rid of some "clanking" I had coming from the diff, especially when dropping the clutch in Reverse. I plan to open my old diff and actually measure the backlash at some point, then set the backlash on the *tight* side of *tight*, reinstall and see how that goes.

I'm hoping the amount of backlash is alright and that it is indeed a mount gone somewhere. The problem is trying to source a BEX rear diff if it is worn...

Edit:
Scratch that there are a whole bunch of Audi's with the same final drive. Link

[onceover]

I've got a rear diff sitting in my garage right now, I'll check for backlash tonight.

[davkav]

I've got a rear diff sitting in my garage right now, I'll check for backlash tonight.

That would be great, thanks man!

[ECS Tuning-Audi]

I have heard of guys installing a stiffer rear diff mount which seems to help with the clunking. This might be an option to look into.

Jason

[walky_talky20]

I've also heard of people stiffening all the mounts, only to have the driveline lash be even *more* pronounced.

The best solution is probably to take out the rear axles, diff, and driveshaft, then swap in a CVT. No more thumping at all. It's Rubber Band ALL DAY!

[davkav]

I've also heard of people stiffening all the mounts, only to have the driveline lash be even *more* pronounced.

The best solution is probably to take out the rear axles, diff, and driveshaft, then swap in a CVT. No more thumping at all. It's Rubber Band ALL DAY!

Probably the least amount of headache alright haha or take out the rear axles, diff, and driveshaft weld up the torsen and have FWD. No RWD no problems.

I'm interested to see what onceover reports back with. If he has the same amount of backlash I will take the diff mount off and see do I have any 'clunk'. Even the softest pull off creates the 'clunk' so I can try it without the mount for a quick test.

[a420]

Dav, have you inspected the center drive shaft bearing? I had similar clunking issue as you described. I recently replaced my whole drive shaft because the center bearing was shot and I didnt want to deal with the u-joint in order to slide the new bearing in.

[onceover]

Just checked the diff. Theres maybe 1-2 degrees of play before the output flanges engage. Definitely less than what you've got.

[G-Ride]

I have heard of guys installing a stiffer rear diff mount which seems to help with the clunking. This might be an option to look into.

Jason

I'll agree with this. I dropped an 034 gearbox mount and an apikol rear diff mount in about 4 years back and it removed that excessive driveline shock entirely.

[diagnosticator]

I presume the same but it just looks a bit excessive...

The amount of angular play in the propeller shaft, as shown in the video, is normal.

[davkav]

The amount of angular play in the propeller shaft, as shown in the video, is normal.

Thanks John, good to know.

I have had the drivetrain 'slop' associated with the rear differential mount failing before and it doesnt feel the same. I will have to investigate further.

I might just go ahead and buy a new transmission mount and rear differential mount and be done with it. I plan on keeping the car for another few years anyway. At least it is two less things to worry about.

I am raging, this time last year I had planned on selling the car, so I parted out all of the performance parts, two of which were a 034 trans mount and an apikol rear diff mount...

[davkav]

double post

[davkav]

Sorry I haven't gotten back to up date this.

I had ordered a new powerflex bushing for my rear differential carrier a while back but it took some time to come in. Got it fitted two weeks ago and the drive line 'slop' and 'thump' is gone. Fitting was easy and I'd highly recommend the bushing over Apikol or other brands from a cost perspective.

The powerflex bushing uses the original bush housing. Removing the old bushing was straight forward with simple tools (hammer and hacksaw).

I have experienced drive line 'slop' before and that is why I didn't think it was my bushing that was causing the 'thumping' sound. As it turns out the stock bushing was not torn or too worn, the mounting hole through the bushing is elongated however and the mount was sliding front to back on the bolt and that is why I was hearing a metal on metal sound rather than the dull 'thump' one would hear when the bushing has failed.

The new powerflex bushing has a circular hole to match the carrier bolt so there is zero movement in the mount now.

[tHatOne guY]

Hi lads,

I haven't been on here in a good while, looks like I will be around for a bit longer now as I am not in the BMW anymore. I never did sell the A4 in the end its back as my daily now.

I have a small issue I'm hoping some of you quattro drive line experts can help me with.

Recently I was realigning my sub frame but the bolts didnt tighten fully as they are one time use only. It took 3 weeks for Audi to get the bolts in for me but during that time I didn't have another car to drive so continued to drive it.

The subframe is fitted with new bolts now and doesn't move at all. Once I got it back out on the road though I noticed there was a thump from the rear end everytime I pulled off, changed gear or simply came on and off the accelerator pedal. Presumably this was down to the front subframe allowing the engine to shunt the whole rear end much like an impact gun.

I thought it was the rear diff hanger but I cannot see any excess movement from it when I have the car on a ramp.

I did notice however that my prop-shaft can move nearly 10* before it engages the rear diff. I have attached a link to a video I made of what I am seeing.

In addition to this I notice a few degrees of play between the two sections of the prop-shaft as well, is this normal?

I could be looking in the wrong area altogether, it may just be the diff mount or rear subframe bushings.

Would you mind having a look at the video and letting my know your thoughts?

Thanks,
Dave

https://drive.google.com/file/d/0Byz...ew?usp=sharing

Would you elaborate as to how you could tell the sub-frame was moving?

I am in the process of putting my B6 back together including torquing the sub-frame bolts and decided to re-use my original bolts, was hoping I wouldn't run into any issues but this has me a little more concerned now.

[davkav]

I could tell that my sub frame was shifting around as I could hear and feel it clunking forward and back when I pulled off. Wear marks around the sub-frame to chassis confirmed that it was moving but only by less than an inch.

You will probably be alright re-using your bolts if this is the first time they will be re-tightened. Mine had been used 3 or 4 times from changing clutches etc.

[tHatOne guY]

Ok. I have noticed some witness marks where the left and right side engine to-chassis mounts bolts up but thought that was normalish. I'll have to keep and ear out for any unusual noises. Before I pulled the engine and trans there was a vibration in the front end at about 65-80....