Hunter04

Hey any idea what it could be I’m thinking U joints but need help! So while accelerating any gear any rpm 30-50 mph the car shakes like crazy but if I let off the gas it stops so this made me think motor mounts but when I slow down off the highway or a pull even while off the throttle it still does it. And while going 30-50 just cruising I can let off the gas and it’s really smooth but then tap the throttle it shakes again. I pushed the clutch and gave it throttle and was still smooth. Any help would be great

Ckforker

Maybe trans mount? How old is it? The rubber degrades from wear and oil/grease.

Banzai

iTrader: (13)

Have you crawled underneath and given it a visual inspection? U joints would be a good place to start. Disconnecting the drive shaft at the rear end is only 4 bolts. A seized or broken bearing would be easy to detect. Ultimately, a lot better than getting stranded miles from home.

LongDuck

Driveshaft: front U-joint is bad. Your symptoms are consistent with it being the front, as it settles out when not under power.

If it were the rear U-joint, it would get progressively worse as you accelerate, and become unbearable at about 40mph - at all power levels.

Hunter04

your exactly right!! I just inspected the rear drive line being that I can’t see the front with out taking stuff off and the rear is just fine then I pulled it out and it was clear what the problem is. I have a new drive line on the way but what should I do to prevent this from happening yo the new one? Trans mount? The new one does have replaceable ujoints

mazdaverx713b

iTrader: (91)

The u-joints just wear out over time, especiallysince the car is more than 30 years old. If the new driveshaft has grease fittings for the u-joints then ensure you grease them once a year. May not take much if any but its a good idea to at least check.

I think its a good idea to check engine and trans mounts and ensure they are good. This will ensure longevity of the new driveshaft.

LongDuck

Driveshafts, even the stock ones - tend to last a good long while (60k-100k miles), as the car is light, with not a ton of torque or power to manage. Typically, the U-joints go bad through age and grease drying up which usually results in metal on metal and then it fails.

I put in a Mazdatrix DS with replaceable U-joints, bought an extra set of spiders to throw in the toolbox for long trips, but don't expect to ever need them. This will likely be the last DS you'll need to buy u less you track the car or add supercharging...

In fact, the original factory U-Joints can be changed, they're just harder to do as the snap rings are on the inside, and nobody has the new bearings of the correct size to fit the cups, hence... aftermarket is the way to go. Glad it's an easy fix,

TimNH

My 85 SE with 190K miles is doing the same so I'm in line for a drive shaft. Where did you get yours? They are back in stock at Rock Auto but have gone up in price quite a bit. There is a place in TX that seems to be the best bet and they have free shipping the the joints are replaceable.

Hunter04

they have one on summit racing I believe for 225 but that is nothing more than a stock replacement I spend 285 and bought one with replaceable u joints free shipping no tax and it said it was going to be here next Wednesday now I’m getting updates that it will be here tomorrow and that was from a place called the driveshaft store.

TimNH

Thanks for the lead. I liked the fact that they don't require a core so I could order it and do it at my leisure. It is just about time for its winter hibernation. So it should get here next week. I need to replace the clutch master after only one year and I need to fill it up before pulling the battery. This was great timing. Thanks.

LongDuck

Unless it's a local driveline shop, they're all made by Mazdatrix - which is a premiere parts supplier for us enthusiasts, and you should support them if at all possible.

I can't speak to Rock Auto parts, as I've had poor luck with their parts accuracy and fitment on several vehicles, so I avoid them.

in this case, buying from a rotary specific parts seller is your best bet, and Mazdatrix has everything you could need to keep your car running, drive shafts included.

www.mazdatrix.com - I get nothing for mentioning them here, they're just a great group of people and I recommend them whole-heartedly.

TimNH

When I bought the car some 24 years ago, I bought many of my restoration parts from Racing Beat and Mazdatrix. My Racing Beat exhaust is still going but the parts are no longer available. I then found a local import car parts store that could get quality parts at good prices and they became my go to source. Buy local. When I moved to NH, the local import car parts store was a joke. I then found Rock Auto and have bought a lot from them. Most of the mess-ups have been my fault and happens because they have so many options and I miss the fine details. They have been very understanding. I'm now retired and so I watch my toy expenditures. So $120 makes a difference to me and I wouldn't be surprised that they get them from the same source.

Thank you for your input. I'm at a point were I will be letting my SE go soon as so it just needs to run. I'm mean, how much longer can the engine last? I only put 300 miles on it this year so the cost per miles has been going up. Hum. I going to be cremated so may the wife could put the urn in the car and have it crushed.

TimNH

The drive shaft arrived today. I rate that as very quick service.

TimNH

I swapped out the drive shaft this morning and as predicted above it was the front joint that was failing. I can't wait to road test it.