drive shaft thump in low gears

[tiguy]

hello everyone this is my first post as I bought my first 318TI a few months ago and like the rest of you love it, not new to BMW's and have owned many including a 73 2002TI , bare with me while I get use to the site and the proper posting catagories, IF I take off too quick I get drive shaft thump, now I see from reading many posts that the universal joint is attached to the driveshaft. Would the universal be the problem for sure or could it be the center hanger bearing and support? I see why now I could not find a universal joint listed at many parts suppliers, that truly sucks. Replace the driveshaft for a univeral ( really) ? Any suggestions would be greatly appreciated as I need to fix or solve the problem, buying a drive shaft is a biggy! Again I appreciate any help or suggestions well I get the bugs out of my car which was stored a couple of years. Cheers and I am glad to be a board such a great site! daren

[cooljess76]

Hi Daren, welcome to the forum. You just gotta get under there and look. There's so many things that could make the thump you're experiencing, our guess is as good as yours. I'd start by checking the center support bearing. If that's good, have a look at the flex disc, trans mounts, motor mounts and differential bushing. Make sure the car is supported well on jackstands or on a lift and give things a good jerk. I'm sure you'll find the culprit.

[teen ti]

Originally Posted by cooljess76

Hi Daren, welcome to the forum. You just gotta get under there and look. There's so many things that could make the thump you're experiencing, our guess is as good as yours. I'd start by checking the center support bearing. If that's good, have a look at the flex disc, trans mounts, motor mounts and differential bushing. Make sure the car is supported well on jackstands or on a lift and give things a good jerk. I'm sure you'll find the culprit.

+1 I had basically the same issue (thought the driveshaft was hitting the body, and was worse the harder the car was driven) got it up on the lift and figured out that it was the motor mounts

[tiguy]

Hi thanks for the kind regards, I did manage to look around a bit well doing other repairs and the flex joint looked real good and the rubber was tight and crack free. I couldn't see the back of the shaft but I have replaced those flex joints on other cars so I new what to look for. Thanks for the tips but I was hoping I could order ahead of time what I thought I might need. I will push on, but it definately feels like the drive shaft is thumping so I will check the motor mounts etc as you suggest. Daren

[zoner]

Might not hurt just to go ahead and replace the transmission mounts anyway- they're relatively cheap, easy to replace, and even if they're not completely sheared or starting to, they usually make a noticeable difference when they're replaced.

Unfortunately, checking things like the center bearing or drive shaft require dropping the exhaust and heat shields... not exceptionally difficult, just a total PITA.

Good luck and welcome!

[tiguy]

Hi Zoner, ok will do I'll price them out, the only reason I thought it might be the center bearing or the u joints is that if I ease into 1st and second its not bad once it third it was hard to notice, Will the motor visibly move like on some cars when revved up if the mounts are shot? or is it basically a visible inspection of the motor mounts themselves. I do have access to a hoist at my dad's place as we have been tinkering with cars for years. Just want to clear up some things before I proceed as it will have to be a quick R & R as its my only daily driver at this time. I read on the site somewhere that you can take the old universal's out and fit new ones in the driveshaft although its a struggle and they have to be welded back in place. Is this indeed possible with some skill? I have installed center bearings before,but I read here that they need to be fitted properly, on my ALFA I dont remember exactly what was involved but think it fitted into place easy without tinkering.? Lastly where would I find suitable replacement universal joints as I cant find them listed for the 318ti anywhere I guess because they come attached to the driveshaft, thanks I appreciate all the help. Daren

[cooljess76]

Hey Daren, I doubt you'll be able to find u-joints "specifically for" the 318ti driveshaft as BMW probably didn't intend for them to be replaced outside of their facility. However, most decent shops should be able to locate, order and even replace them. I know you'd rather do it yourself to avoid any down time, so if this is the case, you're probably going to need to start by figuring out the exact specs/dimensions of the u-joints. Someone mentioned in another thread that 4x4 shops are a good place to go for u-joints and I can concur with that as I used to be a Jeep guy and replacing the u-joints on my lifted YJ was a monthly event.

As for motor mounts, unless they're completely torn and even sometimes not, a visible inspection won't reveal anything since the weight of the motor is constantly resting on them. I have recommended to a couple people to drive the car forward with the hood open while someone observes the engine from outside of the car. It's funny you mentioned your Alfa, I had one too. It was a '91 75 t.spark, crashed it on the AutoStrada going really really fast. One thing that really stood out in my mind about that car was how much the motor rocked side to side when I revved it. And even more weird, a friend of mine also had a 75 t.spark and after I crashed mine I rode to work with him in his for about a month. Guess what, his car had an ENORMOUS I mean HUGE thunk on takeoffs and downshifts. Everyday i told him he needed to replace his motor mounts. They weren't even connected to anything! His motor was literally sitting on the chassis and not bolted down I drove it a few times, the transmission would move forward and back about 2 inches! As far as I know, he never replaced them. Drove that car on shot motor mounts for years until he transferred out of Sicily.

[Monolith]

From a dead stop, floor it while turning left 90 degrees. If you hear it beating the hell out of the transmission tunnel then your ujoints are gone resulting in a destroyed center bearing.

BMW friction welds the driveshafts and stakes the ujoints in place. Aftermarket shafts run about $350 with exchange. Since the ujoints are staked, BMW only sells the complete drive shaft with center bearing installed. Once you get the ujoints fixed/replaced you'll need a new center bearing as well.

If you do the work yourself, be sure and mark each half so it will go back together (if you're not going to have it balanced).

Also, the center bearing has a slight bias towards the front of the car (~4-6mm). It helps to use white-out to mark the bolt positions and the position of the center bearing bracket before removal.

[tiguy]

OK guys many thanks I think I got an idea now what to double check, I will first see about pricing a drive shaft here complete, failing that will go the repair route it cant be any worse then working on one of my ole GTV's or the old 530i's I use to have many moons ago. Locating the u joints will be the hardest part by the sounds of things. Since it appears I wont have any idea what I am dealing with until its apart which makes a R & R problematic. But as one of you mentioned once it is apart a 4 x 4 shop may have the parts needed on hand. The car sat in a barn for several years , and does have a serious power steering leak so there is a possibility that that motor and tranny mounts have suffered from the power steering fluid as well???????? Cheers Daren

[cooljess76]

Just a heads up, these cars don't use regular power steering fluid in their steering racks, they use automatic transmission fluid(ATF).

[tiguy]

Hi COOLJESS, well thanks for the info on the fluid not sure it matters thought until I get the leak fixed, its a bit hard to trace but I believe its the 2 small metal brake type lines at the bottom of the rack unit, they appear to be badly corroded but as of yet I have found any replacements so it looks like I will have to buy the fittings etc and make them up flaring the ends etc like normal brake lines. D

[joe1602]

Really check the motor mounts! I was CONVINCED the drive shaft was hitting the body. I had the same symptoms: Thunking on take off, especially hard ones, in second gear under hard acceleration, and none in 3rd or higher. It does thunk when downshifting & letting off the throttle. Also when driving & decelerating push in the clutch & let the car roll with little/no pressure on the drivetrain. With my car, the thunking stopped whrn I did this, another clue pointing to the motor mount. Hre is what did it for me: While under the car working on the sway bar, I decided to check the mounts, they looked ok but I decided to shake the engine a bit fom underneath & watch the mounts, to my shock I saw the drivers side mounting arm lift off the mount, it is either missing the nut or the bolt has broken. I also witnessed the marks the mounting arm(bracket) were making on the body. I will be changing them today with my son (teenti). Really check those! I was sure it was the driveshaft! I am glad I really checked out the motor mounts. There is an excellent DIY for this procedure on the forum.

[joe1602]

OK Tiguy! Changed the motor mounts & transmission mounts last night. BOTH motor mounts turned out to be broken! Got everything back in placr & took it out for a drive: The same thunking still going on! UGH! I am glad Ichanged the motor mounts because there is a noticeable difference in how the car runs & acts, it took care of most of the noises, but the original thunking that started this process is still there. I have to date done the following: Replaced the sway bar mounts, bushings, drop links, & bushing brackets, both motor mounts, and both transmission mounts. I now have to look at the rear end mount, possibly exhaust, and of course, the driveshaft! (I still can't believe it is the driveshaft as that it looks & feels tight). Good luck. I hope this helps you diagnose your issue!

[Breticus]

Diff could use a shim maybe?

[tiguy]

Hi JOE1602, yes that does suck but like you mentioned the motor mounts and tranny mounts should be done anyway, I am still thinking my problem is the universal and center bearing at least 1 or both. The weird thing is with all this is the car sat in a barn for several years till I purchased it and when I first started driving it it seemed fine but within a week started showing the symptoms like the universal was seized or something. I will do what you did as well and start with the motor and tranny mounts and go from there . I am hoping someone can tell me the size of the universal needed or send me in the right direction for the one the drive shaft will take as I am thinking about removing the old one and refitting the new ,and mig it or what have you in place. But I really need to source one first as I want to have the part on hand so I don't have to take it apart twice or tie up my dads hoist. I know what you are saying about the shaft being tight as I did try to move it once when repairing the exhaust and it wouldn't budge but I couldn't get at the back end of the drive shaft. As far as shimming the diff I don't know is this something that is done over time bimmers by the dealer????