4-Speed In A Blown Application ?

Weird question......

Anyone ever try a 4-Speed in a blown application? Any advantages or disadvantages over a 3-Speed that spring to mind apart from a bit more trans weight and length?

Picture maybe a high overdrive C screw atop a smaller cube but highly strung RPM motor type deal.

Thx.

 

I'm going to say it might have something to do with your 1st gear ratio with an extra gear added in over a 3 spd.

That's my 2 cents
Corey

 

4 speed?? You may be late to the party. Liberty is making a 6 speed for racing applications with a converter or lockup . Ratio is your best friend.

 

Thanks Mike. Is there a rough ballpark for what people are gaining by going to 4 vs 3 ?

 

You want a 25-30% drop per gear, rear ratio 4.30-4.56

 

Back in the day most ran 4 speeds and in the quest to slow the blown cars down they made the 3 speed rule

 

When the revs go up the torque curve usually gets more narrow and pointed . So the higher you rev and a more narrow and pointed it makes an advantage to have less RPM drop on the shifts.

I can't help to think about what was going on in pro stock many years ago when HP/RPM/cost kept going up and up.

 

Mike -TAD hasnt been allowed anything but a 3 speed for about 30-35 years,A-fuel have to be direct drive-no tranny

 

Back in the 90's when IHRA pro mod had 50 plus cars for every race the blower cars were getting to fast...was not talking TAD or TAFC

 

Going off of distant memory the early IHRA days blower cars could not run billet hemi's most ran cast headed BBC style motors rules got changed to allow billet hemi's and the blower cars ran away from the nitrous cars one of the rules to slow them down was going to a three speed .A lot of guys had to run a solid shaft on the 3rd lenco unit rather than changing drive shafts,loops and shiftier mounts

 

the scotty cannon/ johnny rocca era
4 was faster. too fast for the nitrous cars.
also lead to the rear gear rule being 4.56 and no lower.

 

The rule change concerning transmissions in blown pro mods came about after IHRA made billet hemis legal. And if I'm not mistaken this was when they also made a rear gear rule .it was around 98-99

 

So lets say that a person had a very high strung screw motor, and planned to use that RPM range to the max. Mix of 1/4 and 1/8th mile racing. Would a 4/5/6 speed really benefit over a 3 speed? Assuming no constraints otherwise.

 

I think it depends more on if your planning on running a clutch, a converter or a lockup converter. I believe that the lockup and clutch would benefit with more gears but a converter car would be ok with three. I think the gains from the extra gears would be minimal.