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Discussion Starter · #1 ·
A fellow racer was laughingly admiring the (admittably hilarious)
size and bulk of Speedway GT's four speed (stock, of course) transmission. The question was asked, is this gonna be tough enough?
My answer was "we'll see..."
Anybody out there have any speculation on whether or not a stock four speed will survive ten minutes of 8000 rpm in second gear?
What about ten minutes full throttle in third?
Please advise, but don't mention any slick gear oils...that's illegal here because when it blows all over the track it's too hard to remove!
Would the five speed be any better, maybe, and does anyone want to donate one to, say, field test?
What I'm studying lately is all the stock 4 and 5 speed gear ratios,provided by Dennis at Opels Unlimited, mathematically pondering the wild rear gear ratios offered by Risse Motorsports.
All this just to go 60 miles per hour...
Thanks, and keep the pointy end forward.
Jeff
 

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My opinion of the 4 speed is that with new bearings throughout it will survive the sustained 2nd and third runs. If you shift between the two and aren't extremely careful with it. You will coast to a stop and get to pick asphalt out of the counter shaft. Not quite as high of RPM with a stock motor and I did exactly what I have mentioned. The load when you shift at high Rs tends to stress and distort the 1/2 inch or so shaft the counter is riding on and it all lets go. Then again you could get lucky and just grenade the clutch. My advise is try to corner the market on 4 speeds at 50 or so apiece, you can do 10 for the same price of a 5 speed. Then again there was some talk of a 3 speed manual for an opel that may survive better. The 3 speed was on German ebay and if I remember correctly they were pretty fond of it. I'm almost afraid to ask but how many horses are you trying to push through it?
 

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jeff denton said:
Anybody out there have any speculation on whether or not a stock four speed will survive ten minutes of 8000 rpm in second gear?
What about ten minutes full throttle in third?
Please advise, but don't mention any slick gear oils...that's illegal here because when it blows all over the track it's too hard to remove!
It should. We ran the same tranny for three years in our mini-stock. 2nd gear, 3.44 rear axle, 23" tires, 192 hp, 9200-9400 rpms. We had a deeper oil pan for more oil capacity (they run hot), and used Redline shock-proof synthetic to keep the bearings alive.

As long as you don't have to shift or abuse the clutch it'll be okay. Driver once got pissed off and 'dropped' the clutch while trying to get off the track just after a heat, he split the tranny case open and dumped the oil and some parts right on the ground....the car never moved.
 

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Discussion Starter · #4 ·
Thank you, Grant and Bob.
I was really hoping to run the car in high gear to avoid stressing the input gear and countershaft, etc. but in doing the math I came up with 60 mph at 8000 rpm needs an 8.7 gear with 22 inch diameter tires... Not gonna happen.
Adding second gear ratio into the equation with stock rear gear comes out to 7.41, but we won't get 8000 RPM.
So with Risse's 5.28 gears running the four speed in third comes out to 7.21, which is worse yet.
You're right, Bob. Stock rear and second gear.
What modified oil pan are you referring to regarding the transmission? Do you have a trick to increase gear oil capacity?
If you're talking about engine sump, it's covered. We made a beauty. It's heavy duty, deep, kicked out, has a screen, and we made a scraper. A work of art, I think you'd agree...
Hey (straying a bit further) we had the engine in place again recently and got worried about how the oil drains out of the head. Looks like it needs help, maybe some drilling through just above the intake ports and putting in some tubes to drain the oil back to the pan? Have you any thoughts on this?
Thanks a million. It's great to have an Opel expert around...
Jeff
 

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I believe tranny would survive... in 88 I ran a gt on oval track and the transmission faired far better than the clutch.....
about the oil drain...I believe but not entirely certain that the head drain lubes rear main bearing...???
 

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I cut and deepened the stock tranny pan for more capacity.

RE: the oil drain. I add a 1/2" tall tube at the oil drain to slow drainback. The cam won't last at those rpms without it. In fact, Opel started adding these tubes to production heads in the '80's to add longevity to their valvetrains. This will add about 1/2 quart to the oil level however.
 

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