I wrote this in my build thread but figured I'd have more response here.

I ran my RX-7 a couple of weeks ago and ran into this issue on the first day, we're running a three hour enduro in a month and I'm worried what this could be.

After my final run on day two things got weird. Actually before and after. Before, as I went to back out, the car would not roll. I felt like something was broke, but I just forced it back and it got smooth. We thought possibly the pads froze or something although I didn't sit with the brakes down after the session nor did I put the e-brake up.

During the session it was fine. On my way back to the paddock, I felt a heavy pulsating vibration through the shifter, I thought it was possibly pickup from the tires or something. I drove it around a while later in the paddock and it was smooth again. The next day, I started it to warm up and once again, I got that feel through the shifter, but then it went away again. That time it was at idle.

Ideas? I plan on putting fresh fluids in soon. I jacked the car up and didn't see anything out of the ordinary.

 

While I have everyones attention, I have another vibration issue, possibly related?

I get a bad vibration above 70mph or so, it FEELS like it's coming from the rear end, very hard to pin point. Possibly driveshaft out of balanced? New u-joints? I hear a humming noise at low speeds and what not, possible rear wheel bearing?

 

def check the fluids, but when you forced it back you could have damaged the diff gear which would only seize if you ran out of fluid a month ago. before i opened your thread i thought you just needed new syncros in the shifter

 

If I damaged the diff gear wouldn't I have noticed when driving?

There's no way it completely ran out of fluid, I have not seen any under the car while parked or an indication of a small leak on the components under the car.

 

Could be your clutch or pilot bearing related.

Since it happends at idle that rules out the shaft or the rear end.

Has to be between the tranny and engine or the tranny.

Make sure your clutch slave cylinder is working correctly as well.

 

oh i didnt know you where still driving it i thought i was completly locked

and it is possible to completely run out of fluid when the axle has a bad seal but yes you would have noticed

 

If the car was parked and a U-joint was bound up, that would cause the stuck feeling until you moved the car and freed the U-joint up a bit.

 

i would check your transmission mount. after a few autocross' i had the same issue intermittently but rite off of idle. reverse was also feeling bound( in fact if you dumped the clutch in reverse the u joint would bind and make noise. ended up being my trans mount. also during the sessions you would see my shifter move about 3 in side to side while cornering in gear.

 

Hmmmm I'll replace the mount too or at least inspect it, sounds similar to what mine was doing.

U-joint is also on the list.

 

Am I right in reading you can't really replace just the u-joints on a 83 and newer driveshaft? I need a whole new shaft with everything in place?

The car is an 83.

 

sadly, yes

 

The u-joints are replaceable in a 83 to 85. It just takes removing the staked u-joints and replacing with serviable ones. Check out this thread and look for my post. Cost about $100 at a driveshaft shop and then you can replace them and grease them as needed.

https://www.rx7club.com/1st-generati...-tech-1012619/

 

Hmm cool, thanks! I'll look into that.

I found a spare driveshaft that came with the car, is there anyway to check the joints on it while it's out of the car?

 

You can do a visual inspection and then ensure they be spun freely and there insn't any free-play. When I had mine redone, there was rust in them. Since you already have a replacement I'd swap it out and see if the problem goes away. It's a 10 minute job once you get the car in the air. If you hav'nt already, while your changing out the driveshaft, drain and change the trans and rarend oil. About 5 quarts of gear oil should do it. I use one of those orange hand pump to change mine. Makes it simple.

On a side note, is it just me or goes gear oil stink?

 

I'll check, there's some rust around it though so...

I think I'll get the wheels balanced first, then test drive it, if it's still bad swap driveshafts and go from there.

Changing fluids is definitely on the list, we're running it in a 3 hour enduro coming up so...oh and I LOVE the smell of gear oil! LOL Not sure why!

 

Uggh, I hate those hand pumps unless you're talking about a different one than I've used. I've only used the one that screws onto those square bottles of gear oil and you push down and it's not orange. Either I'm super wimpy or they suck they take so much effort. I end up microwaving the plastic oil bottle and it makes it easier.

Now I just go to the local Ace hardware and buy 4 feet of clear plastic tubing that fits into the hole snugly. If you buy too small of a hose, it takes forever to put the oil in, don't ask how I know. Cut the bottom out of a 12oz plastic Pepsi bottle, wash bottle and dry. Take hose, stick it in the Pepsi bottle about 1/2" or so and duck tape it shut. Works like a charm and it doesn't even leak.

Are you using one of those lever action pumps? Those I could see using since you get leverage but I haven't seen one in a while plus the push down types tend to lock you into that brand of oil but I haven't used one in probably 15 years so maybe they've come up with a better one since I've never seen an orange one.

Yes, I can certainly agree that gear oil is incredibly nasty smelling. When I wrenched for a living, I could count on getting that nasty stuff in my hair at least once a week and even after washing your hair three or more times, you can still smell it, it is so nasty I'm having flashbacks.

 

I get a vibration through the shifter on mine when idling on cold startups, but it goes away once the car warms up. I thought this was normal?

 

Simon,

My bet is that your clutch is breaking up. When it jammed, but you were able to free it up, that was probably a piece of the friction plate jammed against the pressure plate. Losing a piece of the PP would then cause the clutch to be out of balance, hence the vibration at idle.

Good luck...



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