Entered a vintage race this past weekend, I'd got the alignment and corner weights set, and a fresh set of tires in an effort to make the top three overall. We were running a new configuration, most of which I've run and during the first session it quickly became apparent I was one of the faster cars in my group. In the second session as soon as we went out on track I started passing cars right away looking to get as many clear laps as possible. I got past 4 cars by turn 3 first lap and then in the next few laps got past 3 Formula Vees. After that I got three clear laps in and could see I was catching the cars that lead the group. Round about lap 7 it was clear I would catch up front running cars but alas running through the esses in 3rd gear the car made a horrible rock crusher sound and shook my molars loose. Third gear was toast, I pulled off at the next station and then limped back the the pits at the end off the station. The salt in the wounds was when the time sheets came out I was fastest of the 18 cars at a 2:56.3 with the next car, a BMW 2002 turning a 2:59.6 and all the other cars were above 3:00.

There were a couple of pluses over the weekend; Datsun was the featured make and I did manage to get in on the group photo, we were pitted next to John Morton of BRE fame and we got to chat with him a little. Also automotive journalist / racer Rick Titus (son of Ford Trans Am driver Jerry Titus) gave my driving a huge compliment while talking to my 21 yr old son and bascially asking how the heck I got a 1200 to go 5 seconds faster than a Formula Vee.

The bright side is I've sourced a ultra close 4 speed to replace the busted mid close 4 speed.

I have disassembled the box and the cluster gear is trashed. As to why it failed either the tail shaft leaking and resultant low fluid levels did it in or as the input shaft bearing and cluster gear bearings seem to have varying amounts of radial play that could be the cause. This is the second cluster gear I've done in. The last one was about 5 years ago, to be honest I just swapped out the damaged parts and never checked the bearings. It's also possible that the A15 motor now makes enough power and torque to do in the box (it is a 56 series)...........anybodies guess is as good as mine.

Tom

good stuff Tom living the dream of datsun dirt cheap racing I hope
any chance of a pic of your engine bay? been hanging for one for a long time

Im thinking its the torque of the A15 as the major contributor to the failure. The forces trying the separate the main shaft and cluster shaft, What was the end float like on the shafts. maybe time to invest in some straight cut gears, even if its only 2nd and 3rd. Maybe one of those Peter Z retrofit Hewland boxes is the go.

Yes, I broke a 4-speed gearbox with a stock A15 with careful driving.

The 56A seems to hold up much much better than the original 56L.

Did it look like these thrashed input gears?

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sticky tires can ruin boxes as well

D First I put a picture of the engine bay in the track photos, see below.

Dave the box I have is a 56A, so it may well be the issue.

Benny, I would absolutely love one of the dog boxes PJZ had, I stupidly passed on one that was very reasonable that just needed a rebuild. The issue is my car might be worth all of $7,000 and adding a $3500 gearbox to it seems a bit much. The 4 speed Option II box will set me back $1500 but it's been professionally rebuilt and it comes with boxes of spares. There might even be a spare mid close cluster gear in the spares. I haven't checked the bearing with a caliper yet but I can visibly move the input shaft bearings well one on the cluster gear.

Circa 2008 I stripped the original gearbox with a pretty standard A12GX but that had 100K on it. After that I picked up the mid-close box from one of the San Francisco area 1200 racers, he did mention I should go through the box because it had quite a few miles on it..........naturally I was under the gun so I slapped it in and back 2010 that munched 3rd. At the time the car made a whopping 73WHP. PJZ had a gear set that as mentioned I slapped in without thoroughly checking everything. The gearbox had roughly 30 events on it and to be honest it puked its contents on 3 different occasions, so that sure didn't help. The box has been rather whiny since just before I put the A15 in, the A15 has been in the car for the last 7 events.

I even looked into modding a Miata/MX5 5 speed and using the competition gear set but after mating up the bell housing buying a $2000 gear set we'd quickly be back at $3500.

Tom

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What are those carbs off? Looks the business.

Those are Keihen FCR carburetors. You can buy them from various motorsport shops.

Keihin is a major suppler to Honda and supplies Triumph, Suzuki, Kawasaki, KTM, and Harley-Davidson. Keihin’s largest shareholder is Honda Motor Co. Ltd.

Nice Post.
I wish I could have gave you every
gearbox I broke before I broke it. Breaking stuff is my business.
Since I figure I can't break a Datsun car itself, I'm good to go. It the last thing on my car that's a Datsun.
Rallying sounds kind of fun. I'm use to the 6 seconds and them Bamm!!! It's over.