ddub

Alright so I'm just trying to figure out what it could be, have a few ideas but want your opinion. I just put in my solid differential mount, but before I go into that here's a little history. For a while now when I start from a stop while turning (only turning not going straight) the rear end vibrates. A few people told me to inspect the u-joints and what have you, and during the solid diff mount install I did this. Now, after putting in the solid diff mount, I went out for a drive and was suddenly getting a clunking noise from the rear end which had never occured before. Happens when I let off the gas or give it more only (like during shifting). As well, when I'm going faster and coasting I hear a weird sound (maybe vibration or something?) coming from the passenger side of the rear (wheel area).

I jacked the car back up and inspected everything I had taken off/put on before and all the bolts and nuts were all tight and fine. So I insepcted the drive shaft and u-joints and found if I grip the drive shaft and try to twist it there is a very slight movement. There is no movement forward and backward, just while twisting it. I then grabbed the u-joints (fronts and rears) and wiggled them with the same result, very very slight movement but nothing too bad. Is it normal for a tiny bit of play or is there supposed to be none at all?

Anyways, another side note is that a couple weeks before the vibration started in the rear long ago, I put in Redline Ultra-Lightweight shockproof differential oil because Icemark said it was okay to run. However since the vibrations started soon after this and had never occured before, it made me wonder if this affected it in some way. I can try draining the oil out and putting some normal stuff in to see if it changes anything, but any damage that is done is done, so I doubt it'll change.

So what do you guys think it is? Driveshaft completely? U-joints? Is that play normal or is there supposed to be absolutely no play at all? Any idea/suggestions are welcome, I'll further inspect things you tell me to and try things you ask as soon as I can and report back, just let me know.

If you need any clarification or whatever, also let me know.

Thanks in advance for any help.

ddub

Update:

Drove car home from friends house where we were looking at it and all. The "sound" I mentioned above seems to be more apparent now; either that or I'm just listening more for it now. Seems to happen at all speeds not just higher ones, and it happens while coasting or on the gas (if I can actually hear it over my exhaust that is) and is coming from the back, not necessarily just the passenger rear tire.

La68camaro

I just bought a 87 turbo rx7 and im having the exact same problem, the guy said it was something he had weilded but it worked for awhile and the weild broke and it started again... ill ask him exactly what it was that was broken..

ddub

That'd be helpful, anything I could check would help narrow the search.

SureShot

The U-jounts should have NO play whatsoever.

One sign the U-joints might be going out is rusty deposits from their bearing seal areas.

The only backlash you should feel in the drive line is a little in the differential, and a very little in the half shafts.

La68camaro

he said it was the rear end mount and that's all he knew

i havnt had time to have it checked out but once i do i'll try to post some info

ddub

So, if I can grab the driveshaft itself (not the u-joints but the actual shaft) and try and "turn" it and there is a very slight bit if play, that is bad and that's most likely the u-joints? That's what we were thinking. Best idea would probably be to replace the u-joints for now and see if it fixes it I guess, right?

ddub

Don't think it's the mounts, checked them all and they seem fine. Plus I just put in a solid diff mount, but I'll check the other mounts again.

Hot_Dog

If the u-joints are loose, than that is the cause of your vibration. From my experience, I've found that u-joints usually last about 100k miles. Sometimes it is hard to detect a bad u-joint because the needle bearings go bad in only one cap.

Hot_Dog
90 RX7 GXL
02 Acura RSX-S

ddub

What about the clunk though? Would that cause a clunking too if the driveshaft is loose because of the bad u-joint? I mean, I can't think of it being anything else especially since the common clunking noise is a broken differential mount, and I just replaced mine (which was in perfect order anyways) with a solid one.

La68camaro

I noticed this clunking occurs when i step on the gas and let go of the gas

it doesnt do it otherwise or at least i havnt noticed that it does.


It's Really annoying though, i feel like my car is about to fall apart or something

Titanium Rat

im not an rx7 expert by far but i know my way around good old high perf precision USA muscle.....there should be NO play in the driveshaft,,,,,in or out,,,or, twisting.

also,,,,again dont know about the RX but with previous experience ALL limited slip diffs need "limited slip additive" to keep the discs from sticking. Yes even if you run the best damn gear oil on the market.

How you like your solid mount,,,,,,i ended up making my own,,,,,,,,,,the factory mount was 170 bucks through mazda,,,,,made mine out of 1/4 steel,,,,,,and boxed it (welded solid!) i dont think she'll break

ddub

Well I haven't been really able to test it yet because of the clunking and all I haven't been driving it much/hard. But when I fix the problem I'm definitely gonna test it out at the track.

SureShot

Do inspect near the U-joint bearing seals for brown (rust) deposits.

FWIW: A solid diff mount will amplify backlash clunks that were there before, but you just couldn't hear them.

DubbayoC

u-joints are not replaceable on stock driveshafts. new ones cost 300-350 i think.

ddub

Wrong.

https://www.rx7club.com/showthread.p...light=u-joints