Long box/short box AGAIN

[jmattox]

Need a long box/short box, whichever one I don't have now. I have 3 or 4 spare FV trans, do not know which they are in various states of disrepair. The trans I have in the car now works like a dream, good shifts, no rattles, etc, but 3rd gear seems too tall. I think I need to be in 4th sooner, after winding engine up in 3rd. Willing to trade leftovers for 1 good "other" box. I am located in Central Florida and up for road trips of 300 miles or so.

John
FV42

813-382-6980

[billinstuart]

The ideal set-up is usually a "transporter" 3rd gear, 1.22/1. 4th should be a 0.89/1. Long box is 4.12/1, short box is 4.37/1. You don't want much rpm drop between 3rd and 4th.

What tracks do you run? How high does your engine rev?

[brian]

John, third gear is chosen in response to the nature of the tracks you run. On the west coast the middle, 1:26 is preferred and it may be due to the topogrophy and hills out here. The 1:22, or tall 3rd, is preferred where running higher speeds when down shifting from 4th. or track layout requires you to stay in 3rd longer. With a middle or short 3rd, the 1:32, which is also the most common among them, it very easy to overrev the motor on downshifts and blow it up.

[Dietmar]

John:

I have to say that I would approach this problem a bit differently. I would first find out what I have, then decide if I needed something different.

It is very easy to determine the gearing that you have in the car right now with a simple turn of the tires ( actually about 5 turns of the tires) and a willing helper.

If this is of interest, let me know and I can give you the steps involved and when you get your "numbers", I would be glad to interpret them and give you your gear ratios.

Hope this helps
Dietmar
http://www.quixoteracing.com

[jmattox]

Thanks for the quick response. Will get back to forum as soon as I have the info about what tranny I currently have.

John

[RickyBobby]

John,

If you find that you are truly in need of a long box, I have one for sale, and very affordable. Feel free to call me here in Tarpon Springs.

Regards,

Bob Browsky
727-942-7668

[jmattox]

Sorry about the length of time responding. Finally got someone to hold the "other" tire while I turned one. Grandchildren help at times! I didn't get to actually measure the number of degrees, but, here is the "data" we colleted. Maybe someone can offer advice.

3rd gear- 1 tire turn produced about 2 5/8 crank turns

4th gear- 1 tire turn produced about 2 crank turns

I think I need a tranny that allows me to wind the engine up quicker in 3rd gear (presently making about 1/2 way from 16 to 17 at Sebring before I see 6500 in 3rd and shift)

Do I need a 4th gear that would allow me to make it to 6000 as I approach 17?

The only places I race are Daytona and Sebring. Would "prefer" one tranny for both tracks, but that is probably not possible.

What I have is a total of 3 1/2 trannys (in addition to the one in the car now) and would like to barter (retirement cash is limited) for another tranny (or 2) that would fit my bill.

Thanks

John
FV42

[jmattox]

Sorry about the length of time responding. Finally got someone to hold the "other" tire while I turned one. Grandchildren help at times! I didn't get to actually measure the number of degrees, but, here is the "data" we colleted. Maybe someone can offer advice.

3rd gear- 1 tire turn produced about 2 5/8 crank turns

4th gear- 1 tire turn produced about 2 crank turns

I think I need a tranny that allows me to wind the engine up quicker in 3rd gear (presently making about 1/2 way from 16 to 17 at Sebring before I see 6500 in 3rd and shift)

Do I need a 4th gear that would allow me to make it to 6000 as I approach 17?

The only places I race are Daytona and Sebring. Would "prefer" one tranny for both tracks, but that is probably not possible.

What I have is a total of 3 1/2 trannys (in addition to the one in the car now) and would like to barter (retirement cash is limited) for another tranny (or 2) that would fit my bill.

Thanks

John
FV42

[BLS]

John,

I'm guessing you have a "short box" (4.375 diff) with an .89 4th gear. According to the chart (link below) from Stevan, that would yield 1 full turn + 340 degree's at the crank.

3rd gear is a guess at 2&5/8, could be a 1.22 or 1.26. need a finer measurement to tell.

This is the link to a comment by Stevan Davis that has a link to his website to download an excel spreadsheet with all the gears. Very useful!

interchange/viewtopic.php?f=2&t=2369&p= ... tio#p14620

Regards,
Barry

[smsazzy]

Turn the wheel 10 times and count the number of shaft turns. That will tell you what the final ratio is. Easy to calculate from there.

[jmattox]

Thanks for the 10 turn suggestion.

3rd gear 10 turns of wheel got 26.75 crank turns, according to the spreadsheet I have a 1.22 3rd

4th gear 10 turns of wheel got 19.5 crank turns, according to spreadshhet I have a 0.89 4th

I realize I need a LONG box for Daytona.

At Sebring I can make it to 6500 in 3rd (as long as battery is good) but when I shift to 4th revs drop to under 4000 and very seldom make it to 5000 before 17. I also understand my carb and manifold are limiting performance, but checkbook is also limited.

Any suggestions or anyone interested in trading 4 and a half trannys for a short box with different 3rd gear and a LONG box. Or maybe a cheap national manifold. Or maybe the lottery numbers for Florida.

John
FV42