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GRM 901 article

I picked up a copy of the February 2003 Grassroots Motorsports today at lunch. In it, they had a 901 rebuild article for their 914 project car. It is a pretty good article with some nice detailed pictures. It would probably be a good companion to red-beard's article.

In the GRM piece, they were having their 901 rebuilt by Gary Wigglesworth from Translog in PA. Apparently Gary is a well-known autocross maven and they alluded to some of his "tricks" in the article. Are you paying attention JP? The article stated, "One of his favorite tricks for an autocross gearbox is to use essentially two second gears, one just slightly higher than the other...Since most autocrossing is done in second or maybe third gears, he uses a much lower third gear than can be found in a stock 901 transaxle"

BTW, there is a sidebar article authored by some guy named Wayne Dempsey. Something about making 914 shifting improvements.
Old 12-30-2002, 09:19 AM
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Ayup, I'm paying attention.
Some day when I have a whole pee pot full of extra cash I'll jump on the trans......raise first, leave second, drop 3rd, add an LSD....dream on.

My brief forays into 3rd while AXing add to driver overload.
Our courses aren't large enuff to stay there for any length of time.
Maybe to mid range of 3rd then hard on the brakes and down shift.

Raising first and second would be mo better but I'd need a new 904 mainshaft or one of Otto's trick units......bout 3k for all the parts, I figure (sigh).

Till then, I'll just abuse the motor ....I do have a 7500 rpm chip.....but no guts

I talked to Eric Frye at the gittogther. He runs at Bremerton where they have lots of room. 80 ish for top speeds are fairly normal, says he. The trailer is ready. Quite sure I can pull 80s in 3rd. Maybe time for another gut check, tho.
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Old 12-30-2002, 11:44 AM
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Yep JP, some of the course layouts make you do alot of shifting between 2nd and 3rd, 3rd to 2nd! It makes for some interesting driving, forget lookin' at the speedo! Your eyes are on the course and you're busy shifting with the right hand and steering with the left. Your foot is always on the gas.
I liked that little trick Brad was talking about to keep you're foot on the gas.....have to try that one.
Geoff
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Old 12-30-2002, 12:00 PM
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Well, One of these days I'll clean and the filter the article....

I submitted it to "9", but never heard anything.

Thanks for the mention

James
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Old 12-31-2002, 04:13 PM
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Quote:
[i]I liked that little trick Brad was talking about to keep you're foot on the gas.....have to try that one.
Geoff [/B]
Sure......he tole me a trick before the last AX of the season.
Popping the clutch to break loose the tires in a tight corner.

Sure enuff, we had one of those. The motor was bogging coming around.... off the bump....& I wuz cussin' .....did I remember his trick?...of course not I don't do my best thinkin' during these runs.
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Old 12-31-2002, 06:05 PM
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I read the article in GMS. Interesting.
In my case, if I'm wide guts in second and shift to third, it drops me right into the fat part of the torque band for my motor.....around 5K rpms. A silght drop, say to 6K wouldn't be better, me thinks. I may run out of that gear too quickly.

Frankly, I don't have enough 3rd gear AX time to know what I need. Ours are more of the slow type described in the article.
Bremerton AX is on the list for next season. 3 or 4 of them and I may have a clue.
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Old 01-01-2003, 08:26 PM
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speaking of 901's

When you are building a big four (2.2) w/carbs, does one benefit from putting a different first gear ratio in? It has always been my opinion that first gear is pretty tall but I am wondering how it will feel with an extra 45 horsepower?
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Old 01-02-2003, 09:23 PM
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Re: speaking of 901's

Quote:
Originally posted by Peter_Hinkle
When you are building a big four (2.2) w/carbs, does one benefit from putting a different first gear ratio in? It has always been my opinion that first gear is pretty tall but I am wondering how it will feel with an extra 45 horsepower?
I have a 2.4 and short tires (205/50R15) and 1st gear feels quite short. Almost worthless in fact. The car will roll off the line in 2nd with no prob.
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Old 01-03-2003, 08:47 AM
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Replacing 1st gear is tough. A "gear" is really a gear set, a meshed pair of gears, one on each shaft. The Center of each gear is the fixed position on the shaft. So when you change a gear ratio, you make one gear larger, and one gear smaller, but the center to center distance always remains the same.

1st Gear is about as low as you can make it. The drive gear is tiny, barely larger than the drive shaft. It is also unique. No other gear has the same inner dimension.

2nd Gear, on the drive shaft, is actually a machined piece of the shaft, so no changes there. Well, unless you find the extremely rare shaft and gear that are changable (This was never on a stock 914). You are talking major bucks here.

So this leaves us 3rd, 4th and 5th. And what you do with those gears will depend on what you want to do with the car. Want closer gear ratios for Autocross? Go for it. You could also accomplish this with 50 series tires, however the speedo will not read correctly. Want to increase the high end speed with taller gears? Go for it! This is not something to be entered into lightly or with wallet held closed. Think in terms of thousands of dollars.

James
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Old 01-04-2003, 08:37 PM
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Quote:
Originally posted by red-beard
Want closer gear ratios for Autocross? Go for it. You could also accomplish this with 50 series tires, however the speedo will not read correctly.
Palo Alto Speedometer or North Hollywood Speedometer can modify your speedometer to read correctly with non-stock tire diameters. Not cheap, but far cheaper than virtually any tranny modification.
Old 01-05-2003, 06:56 AM
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