Zarengo Posted January 21, 2019 Share Posted January 21, 2019 I have an issue I can't seem to shake. My 85 BRAT vibrates when I drive over 45 mph like clockwork. The vibration sounds like a low, constant rumble. And I can feel it on my back. The vibration seems to ease a little when I let go of the accelerator (above 45 mph), but it does not go away. It then eases again when I make it past 70 mph, but doesn't go away entirely. I have brand new u-joints in the drive shaft (it clicked as I moved) and the vibration was there before and after I changed them. It also has brand new inner & outer tie rods, ball joints, front wheel bearings, front axles, shocks in the rear, front rotors, rear brake shoes. I had a tire alignment (needed to anyways after the tie rod change) and even though my tires have maybe 1,700 miles on them, I rotated the tires and balanced them anyways, but the vibration stayed the same. Other than the rear axles, which for the life of me I can't find at all, new, used refurbished or any at all. I can't figure out what could be the cause. I keep seeing almost everything pointing to either the tires or the axles, but with no new rear axles to be found and tires already rotated/balanced, I'm out of ideas. Any and all help is appreciated! Quote Link to comment Share on other sites More sharing options...
Subasaurus Posted January 21, 2019 Share Posted January 21, 2019 you can rule out your rear axles by lifting your vehicle, putting it on jackstands, put it in gear and letting the car idle, and see if the axle is bent by taking a look at them. i've had remanufactured CV axles bent before, and the vibration is insane at 40mph. Quote Link to comment Share on other sites More sharing options...
bratman2 Posted January 21, 2019 Share Posted January 21, 2019 (edited) You can pull the rear axles, clean the joints, grease and reboot. Swap them left to right, if they are still good. I have a vibration in mine when I get close to 60. Honestly I think mine are the tires. Have no idea what yours is. But, check your motor mounts and transmission mounts. That is my only guess being you have covered about everything else. Unless you got a bad axle out of the box. That has happened to me, more than once. Oh, you didn't mention rear wheel bearings. You might want to check them also. Edited January 21, 2019 by bratman2 Quote Link to comment Share on other sites More sharing options...
DaveT Posted January 21, 2019 Share Posted January 21, 2019 If it is a low hum, I usually found that to be the u joint bearings shot, throwing off the balance. Wheel bearings could do that sort of low note vibration also. If it's more of a shimmy like 1 pulse per revolution if the tires, that's more likely related to alignment, suspension and all that stuff. I did have a weird 1 ppr shimmy when a tire partially failed. The tread separated from the steel belts, forming a bubble. It would be obvious at some speeds, and dissappear at others. 1 Quote Link to comment Share on other sites More sharing options...
Zarengo Posted January 21, 2019 Author Share Posted January 21, 2019 Thank you for the responses! And you are right bratman2, I didn't change the rear wheel bearings, yet. I actually already have a set of wheel bearings and seals I planned to change as well. As far as the axles go, since I can't find any complete replacements, I also went and bought boots and grease to put on them. Just haven't gotten around to doing that this winter. As far as the mounts go, I know I need to change mine too. But I get some people saying there are 3 and others that there are 4 mounts. How many are there and where can I get them? I know I can find them at Rockauto and Ebay, but I don't trust either too much. I hear that switching axle sides helps in case there's wear in the joints. The theory being that switching them uses the side of the bearing that is less used. How true is that? And in the worst case scenario where I grease, reboot, switch and still no dice. Where can I source reliable rear axles? Quote Link to comment Share on other sites More sharing options...
Dee2 Posted January 21, 2019 Share Posted January 21, 2019 Raise the car up and see if there is any play in the wheels by rocking the 12 and 6 o'clock positions. Movement or klunking sound will indicate worn bearings. Quote Link to comment Share on other sites More sharing options...
Steptoe Posted January 21, 2019 Share Posted January 21, 2019 if you can find a set of wheels and tyres to swap over or have all four inspected closely or run on a wheel balancer Quote Link to comment Share on other sites More sharing options...
bratman2 Posted January 21, 2019 Share Posted January 21, 2019 The rear axles will have any wear in one direction. So swapping them will extend their life tremendously. There are four mounts. Two engine and two transmission. I'd have to check but the first ones I ordered off Rockauto, maybe 7-8 years ago, were the wrong ones. I will try and find the correct number. I think General Disorder provided me with it many years ago. How many miles you have. I still have my original rears with 250k miles. swapped left to right with new grease and boots maybe 12 years ago. Mine is a 87. Quote Link to comment Share on other sites More sharing options...
bratman2 Posted January 21, 2019 Share Posted January 21, 2019 Oh, one other thing. If you do order anything off RockAuto use 84 as the year model and double check the part numbers from another source. Quote Link to comment Share on other sites More sharing options...
Zarengo Posted January 21, 2019 Author Share Posted January 21, 2019 I have a 1985 with 179k miles on the clock, got it about 2k miles ago. From the looks of it, about 95% was original when I got it (mostly for worse). It seems that every part I change is original too. Quote Link to comment Share on other sites More sharing options...
bratman2 Posted January 21, 2019 Share Posted January 21, 2019 Lol, are maybe old used parts!! Quote Link to comment Share on other sites More sharing options...
Zarengo Posted January 21, 2019 Author Share Posted January 21, 2019 Possibly. But judging by the OG exhaust manifold I changed, which was plagued with rust holes EVERYWHERE I wouldn't be surprised if most is original. I'll try to replace the rear wheel bearings and swap the axles and see what the results are after that. But I would appreciate more info about those mounts. Quote Link to comment Share on other sites More sharing options...
bratman2 Posted January 21, 2019 Share Posted January 21, 2019 Looking hard as I can. Went to my profile Looking at the Rockauto selection for a 84 I am pretty sure the Beck/Arnley is not the correct one. I think the DEA A6700is the correct one for the transmission. Advance Auto list it also as fitting, I have an account with them. I believe the DEA A6702 is the correct one for the front. Not 100 per cent sure and not sure I could tell from looking underneath ,my Brat. I would suggest cross reference the two I suggested. Maybe someone else will post that purchased some a decade more recent than me, lol! Quote Link to comment Share on other sites More sharing options...
sparkyboy Posted January 21, 2019 Share Posted January 21, 2019 (edited) I once replaced all the bushings and what not on my camaro chasing a tiny vibration fron 65-70 mph. She needed it anyway, and i had some lowering springs i wanted to install... My problem? A slightly out of balance tire, but yours does sound like driveline? My 86 GL had a tiny shake in the highway due to a loose motor mount, it felt like it was coming from behind the trans while driving. Get her up on 4 jackstands and grab that stethoscope and get back to us! And yea switch all the axles and keep the good ones, i use the cheap ones (like $45) with the stainless steel looking cup and i get about 10,000 miles on an over cambered homemade 2" lift and suffers from some smokey ej22 burnouts. Edited January 22, 2019 by sparkyboy Quote Link to comment Share on other sites More sharing options...
atw Posted May 11, 2020 Share Posted May 11, 2020 Zarengo, did you ever id or solve the problem? Something similar going on with my (340k) '86 brat: a rumble, vibration between 45 and perhaps 60 mph. My excellent old school mechanic has been trying to figure this out for a year or two, but after largely eliminating all of the things mentioned in this thread and more, it looks increasingly like the transmission. Any luck with yours? Quote Link to comment Share on other sites More sharing options...
carfreak85 Posted May 12, 2020 Share Posted May 12, 2020 Last visited June 2019... Quote Link to comment Share on other sites More sharing options...
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