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transmission issue on a oval track rx7.

Old 05-03-15, 09:03 AM
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transmission issue on a oval track rx7.

i apologize is this not the right place to ask this question but i need help. first of all a little story behind. last year a good friend of mine decided last to go circle track racing with a rotary, 1/4 to 1/2 mile local circle track. i just join his team this year to help him with his mechanical stuff. the car is a 83 rx7 with a street ported 13b with a ida 48 carb, 4.77 kia rear end gear weight 1811 pound with driver and 5 gals of gas. anyways engine and suspension wise is perfect but we been having issues with transmissions. we went thru 3 transmission in the past year. kept breaking the tail shaft housing in two. so we sorted that because the engine was still in stock motor and transmission mounts. we put solid ones and got a new drive shaft. now on our last transmission we were having issues with the tail shaft seal coming off and we put silicone, lock tite and still came off and now last night the actual tail shaft bearing came off in the feature. i'm dumb founded. i never experienced or seen something like this. i don't know what can cause it. does anyone experience this problem in the past and how did you got it resolved? i apreciate any help or suggestions please. thanks

eddie

Last edited by eddierotary; 05-03-15 at 09:07 AM. Reason: grammar fix
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Old 05-03-15, 10:01 AM
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Lose the solid transmission mount and fix your U-joint angles. The U-joints must be the same angle relative to the driveshaft, and angles of more than about 3 degrees significantly shorten tailhousing bushing life and U-joint life.

Also, get your driveshaft rebalanced. Is your new driveshaft "NEW" or a used one, or rebuilt with old parts?
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Old 05-03-15, 12:35 PM
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yes is a brand new driveshaft made for the car, high speed balanced. we told fleetpride that need to be high speed balanced because of the speed we are turning. so you think that still miss alightment of the trasmision and driveshaft?
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Old 05-03-15, 09:31 PM
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Tailshaft bushings will die quickly regardless of what you do, so all you can do is make sure its life is easy.

IE - Make sure the U-joint angles are correct when at acceleration ride height, make sure they aren't excessive, make sure your tailhousing has the sheetmetal oil feed channel in place, make sure the trans is kept full-to-overfull (I'll fill it with an extra half quart by putting the left side on stands).
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Old 05-04-15, 03:40 PM
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Great advice on the overfill remark. I need to do that with mine as well and I then end up with the car spitting oil out the upper breather and filling the car with fumes. I agree that the extra fluid is necessary, so I changed the breather for a fitting and ran the hose up to a catch can bottle. Got rid of the smell and dripping after a race and I have never lost a rear seal or tailshaft bushing.

Eric
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Old 05-04-15, 05:29 PM
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I think the old school race trick was to weld material onto the end of the tail housing and then rebore the tail shaft housing to fit a needle bearing/seal.
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Old 05-05-15, 08:56 AM
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Cool, interesting. Now if I could get the stock box to live with 9,000 rpm shifts, it would be worthwhile, LOL.

Thanks a bunch

Eric
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Old 05-05-15, 10:00 AM
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Yeah, my TII box and my FD box didn't like 9,000rpm either. Sometimes lock me out till speed drops.

Just drove a RX-8 and it shifted nicely off the revlimiter (just over 9,000rpm I think).
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Old 05-09-15, 08:39 PM
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Differential

You guys are scaring me. I've been doing all those things and knock on wood same tranny and rear end. Imagine a bunch of FWD cars and one Rotary spins side ways in the pack shifting near 9-10 grand when you grab 3rd gear, or they hit your rear bumper and you pull away slideways. Not so lucky today Eddie, we threw the belt on lap 1 coming through the field. You left out one thing that might have started the problem before they got the car. Hint: we learned it last night. I told them I have a GT Panhard and Tri Link left. That would help with the pinion angle. The chassis may be doing all kinds of stuff with the watts linkange going roundy round, and its the same repetitive forces every turn going left. That car has definitely taken more hits than mine. Fell off the hauler once at speed on the highway.

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Old 05-10-15, 09:13 PM
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Originally Posted by BLUE TII View Post
Yeah, my TII box and my FD box didn't like 9,000rpm either. Sometimes lock me out till speed drops.

Just drove a RX-8 and it shifted nicely off the revlimiter (just over 9,000rpm I think).
You also need a hardened yoke for that to work. Unfortunately Those are hard to come by.
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Old 05-11-15, 09:30 PM
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Fixed

I think the old school race trick was to weld material onto the end of the tail housing and then rebore the tail shaft housing to fit a needle bearing/seal.


You also need a hardened yoke for that to work. Unfortunately Those are hard to come by.
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Old 05-13-15, 09:58 AM
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Ahhhh.... that makes more sense. I was wondering if the comment was actually supposed to be about the forks, LOL.

Eric
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Old 05-13-15, 08:07 PM
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well after measuring everything the engine was out of aligment. we aligh it better and so far the transmission is holding together
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