PandazRx-7

iTrader: (18)

My car jerks for a split second between shifts...also when cruising in gear and letting on/off the throttle.
This slop was dramatically reduced when I switched out my tranny a month ago...BUT still some slop left. Can anyone tell me what else this can be...rear diff, driveshaft, etc.

As far as my bushings, I just changed them all...including the pillowball bushings.

Thanks

InsaneGideon

I take it the power plant frame is in correctly... though one would suspect it was during a tranny swap.

PandazRx-7

iTrader: (18)

Another thing I noticed is when I jack up the rear and spin the wheel while it is in first gear...there is some "space" before it catches the gear. I'm assuming this is from the gear in the Diff...I just don't know how much is acceptable.

influx

I've noticed the same thing with my car. I don't know if it means the diff is worn or something. It's also not too smooth when I go off and on the throttle.

WaLieN

I have a similar problem -- I'm hoping an engine torque brace will help alleviate some of it.

rxrotary2_7

replace your motor mounts before adding a TB.

PandazRx-7

iTrader: (18)

I was thinking of checking the motormounts first... any suggestions on how to check it real quick without getting under the car. (Maybe rev the motor and see if if theres too much movement?)

Also, back to the Diff...would that extra play be from a worn Ring & Pinion, because my LSD seems fine.

rotary-tt

Could have blown one of the rear diff fluid-filled mounts...

PandazRx-7

iTrader: (18)

You know I just changed the Diff Bushings 7 months ago...But there's a good chance that it probably did blow again since my old tranny had so much play.

Also when I shift real hard into 2nd gear at high RPM, I get this very alarming "bang" noise. I checked my PPF when the tranny was out 2 months ago and it had no cracks at all. So I guess, Im narrowing it down to the Motor mounts, Diff Bushings, or even the Ring & Pinion inside the diff...?

Man this slop gets me irritated!

rotary-tt

Let me know if you figure it out as I have the same bang on hard shifts and lots of slop. I may just have Nucar Mazda look at it. They are pretty good with this stuff and they have a shuttle back and forth from where I work. Need the anti-freeze changed as well. I'd look at it myself but I don't have time...

WaLieN

Agh, I have the same symptoms. Hrm, I'm hoping it's anything but the PPF or the Motor Mounts -- do let us know how it turns out.

PandazRx-7

iTrader: (18)

I was also wondering if maybe the driveshaft can be the problem. Mine has over 120,000 miles on it. I'm sure there's some wear on it after all those miles...Any reports from anyone having to change the driveshaft due to bad joints?

Just remembered something too...the car has a strange vibration when I'm letting go of the clutch in first gear, especially going up a slope. It only happens at the friction point until I fully let up the clutch. It lasts only for a second.

Any feedback on that would be great as well.

rotary-tt

Highly doubt that it's the u-joints. The whole car will get a rumbling vibration which increases with speed when this happens. I lost one on my 2nd gen and I'm sure it's not that.

clayne

Check the back of your PPF - sounds like it's toast.

PandazRx-7

iTrader: (18)

bump

Mahjik

iTrader: (1)

I agree, check the welds on the Power Plant Frame.

David Beale

I posted this to the big list a month or two ago. It's a good place to start, before panicing.

Well, as my car is up on jackstands for the winter, I volunteered to make the following measurements.

Technique:
Differential play -
1. Raise car off ground (rear wheels, anyway). Use jackstands.

2. With car in neutral, slide under and mark differential input plate with a flow marker. One mark at each of two adjacent universal bearings (90 degrees). The bolt between the bearings will then be 45 degrees from each of the other marks. By eye, split the distance from the bolt to each "U" joint mark in half. These will be 22.5 degree marks. Now split the space from this mark to the "U" joint mark - these will be 11.25 degree marks. You can go further, if desired, but I doubt you will be accurate enough to be meaningful after this.

3. Apply parking brake (if you have no parking brake jam the wheels to the ground with blocks so they cannot turn).

4. Try to rotate each halfshaft at the differential outputs - mine had no play, and I suspect if there is any, something is toast.

5. Now, rotate the drive shaft and measure how much it turns. Mine turned almost exactly from one to the next of the 11.25 degree marks.
This is the differential rotational play (approx. 11.25 deg. in my case).

Transmission play -
1. Release parking brake and place transmission in 3rd gear (had to choose one, and this is the "best" gear for the 3rd gen).
2. Slide back under and now check the driveshaft play at your marked diff. input plate. I saw approx. 5.75 degrees (half way between the 11.25 degree marks). You can check to make sure there is no play in either "U" joint. If there is any that you can notice by eye, the "U" joint is toast (and, I suppose, so is the driveshaft as they are one piece).
This is the transmission rotational play for 3rd gear (approx. 5.75 degrees in my case).

The total rotational driveline play will be the two added together (approx. 17 degrees in my case).
I suggest, when drag racing, this play should be taken out at the line with the brakes applied, before going at the lights. I'm sure the drag racers out there already know this.

Anyone else care to make the measurements and post the results?

BigIslandSevens

iTrader: (4)

Very nice list! A Easy way to test the motor mounts is to start the car, raise the hood, apply the parking brake, and have someone put the car in first gear and start to engage the clutch. If they are bad( driver side mostly) you will get alot of movement like the engine is tryng to jump out the passenger side of the car!! Some movement is normal....alot or more than you think should be there is not normal. If you get under the car you can get a pry bar and test the movement of the mount directly. My PPF(power plant frame) cracked at the trans side welds. Check both ends for good measure. As far as the diff. free-play, I like the listed measurements above. How does that translate to turns of the pinion David/( I mean is it like a quarter turn or half turn of movement etc...)

Zyon13B

-=UPDATE=-
I had this problem for about a year, and now I finally solved it.

First what didn't work: I replaced all my mounts[including diff], old ones seemed good, neways. I checked PPF over and over, always good. Looked at clutch fork, good. I did the test two post up, it checked out. Diff brace didn't help[helps wheel hop though]. New toe links and trailing arms, nope. Also replaced my bushings, they stopped the rear end clunk, but still no solution.

After a year of this I was having doubts. Finally I tried two things at once and it was gone. I checked the clutch pedal, and brought it up to spec[it had a little extra play] And, the thing I believe finally did it, I checked the TPS, and the closed-to-light throttle voltage was off. I fixed it and it's like a brand new car.

So Pandaz, if you still have the problem, check your TPS.

Ryan

gdnimr0d

iTrader: (4)

how would one check the closed to light throttle voltage?

Zyon13B

Right here:

http://www.rx7.org/Robinette/tps_adj.htm

Zyon13B

Auy updates Pandaz?

PandazRx-7

iTrader: (18)

Actually, I'll let you know this Sun. I'm changing out the diff bushings and fuel filter. Then I'll check the TPS just to make sure it's at spec.

Again, I fixed most of the drivetrain play by swapping out my motormounts with Urethanes and now it only has a bogging/bouncing symptom in first gear when I let off the clutch at the friction point. Definitly feels like the diff is bouncing around...