3rd gear engagement - SCCR box

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3rd gear engagement - SCCR box

Postby mmacquee » Thu Dec 30, 2010 5:37 pm

Just put together a SCCR box, new gearset from England, rebuild kit from VB. The ball bearing on the 3rd motion shaft required assembly with shims, since the race is a different thickness than the bearing originally supplied. I assembled the shims per instructions - but now it looks as if I am not getting full engagement of 3rd gear. 1st and 2nd engage okay, but it does not appear as if the outer hub of the 3-4 slider is slipping fully into place on the 3rd gear engaging teeth. Is it possible that somehow the shim pack is wrong and I need to tear it down again, use thinner shims in order to move 3rd gear closer to the shift hub, as it were? Suggestions appreciated - thanks.
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Re: 3rd gear engagement - SCCR box

Postby JB » Fri Dec 31, 2010 11:13 am

you need to shim per the shop manual. Use a Bentlly or Autopress manual for best results.
Possibly a bent 3-4 brass fork.
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Re: 3rd gear engagement - SCCR box

Postby 44woodie » Thu Jan 20, 2011 12:55 pm

I have had this same problem. Changed shift forks twice, no change, shit lever will not engage fully --will not move as far forward as it does in 1st gear. Works fine for two or three races after rebuild and then starts popping out of 3rd gear under power. Have checked and double checked against a stock box but can't figure it out. Any other suggestions?
Also looking to BUY a spare SCCR box or parts if anyone has them. Thanks
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Re: 3rd gear engagement - SCCR box

Postby Sprite33 » Thu Jan 20, 2011 2:11 pm

I ran a SCCR gearbox for around 10 years. I had a performance shop do the conversion for me. It work perfectly until I shifted to 3rd in a race and "bang' with no drive except for 4th gear. The same shop looked at it and had to order another kit to repair. After that all seemed fine until it started randomly popping out of 3rd under power. I could hold it in gear but that was cumbersome while racing. The shop took it apart several times and could never get the problem to go away. I finally bought a dog ring gearbox and only use the SCCR gearbox as a backup, which I have not needed yet.

Someday I am going to take a close look at it to see if I can figure out why it pops out of 3rd. I took a quick look at is once through the side cover and it looked to me that the gears were not fully engaged but the shop said it was fine. I still think it is not fully engaged in third. If I ever get around to working on it I will let you know what I found.
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Re: 3rd gear engagement - SCCR box

Postby mmacquee » Mon Jan 31, 2011 1:39 pm

My problem now is that between today and the first race of the season all of my garage time is spoken for, in terms of doing what is needed to get the car ready to race again. So the gearbox will have to wait for a little bit, have another complete SCCR unit ready to go plus a tested and proven street box spare, so there's no shortage there. I did replace the 3-4 fork, making sure that the fork gap was in spec, and that made no real difference.
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Re: 3rd gear engagement - SCCR box

Postby Charlie Tolman » Tue Feb 01, 2011 1:46 am

I had a straight-cut close-ratio set of gears in a transmission, and had problems with popping out of gear. It was caused by worn synchro-hubs and/or worn synchro teeth on the gear.
Of course, proper shimming is always required.

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Re: 3rd gear engagement - SCCR box

Postby Phil » Mon May 30, 2011 9:46 pm

It is due to shi!!y (questionable) replacement bearing(s)???
Don’t ask how I know! :evil:
Look up John Twist youtube video (University Motors Ltd) for detailed explanation.
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Re: 3rd gear engagement - SCCR box

Postby mmacquee » Mon Aug 15, 2011 12:56 pm

Yes, it was due to shi??y replacement bearing. I finally had time to tear the box down again, removed the replacement bearing and installed a nice used 3rd motion shaft bearing from my big box of gearbox spares. Third gear now engages fully. I'll leave the stock box in for the final races of the season and swap again during the off season -

so the lesson is 1/ if you use the new bearing and the shims ignore the murky instructions that are packed with it and shim it up so that the inner race is as proud of the outer race plane as the old style bearing or b/ re-use a good old style bearing.
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Re: 3rd gear engagement - SCCR box

Postby Charlie Tolman » Tue Aug 16, 2011 12:46 am

Good suggestion and good information. Thanks.

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Re: 3rd gear engagement - SCCR box

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