BlownBird

I am running a 12 bolt with 4 series spool. I am looking for a 3.73 Pro gear, as I have destroyed my 3.73 Richmond street gear on the first launch. I have been searching the web and have found nothing... Can anyone lead me in the right dirrection on this???
Every set of pro gears I have found start at 4.11, I would actually rather be a 3.55, but have settled on the 3.73 because of the 4 series spool.


I am asking this in the Drag race forum because you guys would be more knowledgable with this sort of thing.

Thanks,
DonB

AlkyIROC

Put a taller tire on it and run 4.11 gears. Pro gears are just a softer metal. They're designed to flex under hard stress instead of break. The downside is they're too soft for street use as they'll wear out quickly.

ModifierRacing

Pro gears cant be driven for longer than 50 miles at a time. As for your gears breaking, were they setup correctly? In my 3500 lb 69 firebird I had a set of 3.70 richmond street gears in a 8.5" 10 bolt and ran that way for 200 passes till I pulled it out and put in a ford 9". My firebird has around 700 ft lbs on the bottle. They also had 20,000 street miles, and has been in a slower car for the last 2 yrs.

BlownBird

Stephen 87 IROC
Well... I am already running a 30" tall tire and the 3.73's will have me over 8000rpm as it is, so for me the taller tire/4.11 combo is not an option.

ModifierRacing
This is strictly a drag car, so no street use at all. the car weigh's in at 3480 with me in it, and has over 1100hp and even more tq. At this point the pro gear is a must.

The breakage happened within 20' on the first pass. Released the trans brake (3400 on the two step), as it was climbing up it broke the gear set. It appears as tho if the rear had not failed, it would most likely have gone onto the bumper, it was going up instead of out. I will tighten up the front shocks a bit to prevent that from happening again, but in the mean time I need a set of 3.73 PRO Gears.

Thanks,
DonB

AlkyIROC

You're not going to find a street gear ratio in a Pro gear set. Even if you go with a Ford 9", the Pro gears start at 3.89 ratio.

BlownBird

ok, thanks for the help.

onefast85

why is it spinning so many rpm's?i see your big mph for the et but seems like you wouldn't need to turn it that high?is the converter to loose?a blower motor or a heavy sprayed nitrous motor will run faster if you lug it a little.

i ran 4.10 pro gears in my 12bolt with a 29.5x10.5 slick and only turned 7500rpm but went 155mph.i broke a couple sets of street gears myself but i think it was from tire shake more than anything else

you et should be in the real low 9's.

AlkyIROC

Doh! I never even noticed that. 10.0 at 144 mph is a slow ET for that mph. Something is definitely wrong there.

I have 30 x 10.5 tires with 4.56 gears and only go to 7000 rpm through the traps. My 10.10 run is only 130 mph.

Many years ago when I had a 383, my tire/gear combination was wrong. 3.27 gears and 26" tall slicks going to 6800 produced 12.0 runs at 117 mph. MPH was too high for the ET because the gearing was wrong. Going to 4.10 gear dropped the ET into the low to mid 11's (big block at the time) and the mph was still roughly the same.

I'm wondering about the accuracy of your tach?

bjm323

Richmond Pro Gears start out at 3.40 for the Ford 9".

http://www.richmondgear.com/NHRA.pdf#search='Richmond%203.40%20Pro%20gear'

BlownBird

That was the times for my old combo, it never made a full pass.
This new combination is setup to COMPETE in extreme street, should be 160+ mph

AlkyIROC

Not sure how you got that page. Ahh. Found it. New gears for new season.

This is all I can pull off the Richmond site about the 9" gears they offer

http://www.richmondgear.com/01pdfs/pages6,7.pdf

The Richmond gear calculator says a 3480 pound car with 30" tires, 1100 hp and spinning to 8000 rpm should have 4.48 gears for the 1/4 mile and will get 160 mph at 8.65. You'll need more gear.