Low FIRST Gear 904 transmission

Posted By: barracuda7

Low FIRST Gear 904 transmission - 09/14/10 01:28 AM

I want a Low 1st Gear for my 904.

I did a lot research and it seem to come "if I want Low 1st Gear, I will have Low 2nd Gear". Like the 904 Ratio is: 2.45/1.45/1 if I change/swap to Low 1st Gear, it will be: 2.74/1.54/1 , no other option.

But I want 2.74/1.45/1

After study the 904 by myself, I release that if I want Low 1st Gear, I will need new REAR ring gear & smaller Sun Gear(other side Sun Gear stay the same 28 teeth)and possibility new Low-Reserve Drum.

Anyone make a Gear Set to lower 1st gear ratio only?

Or anyone have modify the 904 that way, can you please let me know how did you do?

Thank in advance

Posted By: Wedgeman

Re: Low FIRST Gear 904 transmission - 09/14/10 02:33 AM

Another option would be to pick up an A999 trans
with 5 disc clutch and stronger internals...

Dan

Posted By: RapidRobert

Re: Low FIRST Gear 904 transmission - 09/14/10 02:47 AM

. I want to eliminate 1st and 2nd (to save a few lbs) & start in 3rd (6:20 rear gears) for next years circle burner (904).

Posted By: barracuda7

Re: Low FIRST Gear 904 transmission - 09/14/10 07:19 PM

Quote:

Another option would be to pick up an A999 trans
with 5 disc clutch and stronger internals...

Dan

This swap will completely changed ratio at BOTH 1st Shift and 2nd Shift.

I need lower ratio at 1st Shift only, this ever done before?

Posted By: babarracuda

Re: Low FIRST Gear 904 transmission - 09/14/10 07:59 PM

I don't think it is possible. Call Pro Trans in Lancaster CA. He does all sorts of changes to 727's and 904's. In racing the complaint is that when you put in the low gears the jump from second ti third is too much. Some say that on a under 500 HP car you lose too much with the bigger ratio drop. I raced a 360 and two of my friends raced 340's with the low gear and never had a complaint. I guess that I don't understand why you want the 1.45 second gear?

Posted By: Wedgeman

Re: Low FIRST Gear 904 transmission - 09/15/10 02:49 AM

Why would you want to go slower after a faster launch ?

Dan

Posted By: barracuda7

Re: Low FIRST Gear 904 transmission - 09/15/10 04:28 AM

Quote:

Why would you want to go slower after a faster launch ?

Dan

I dont want go slower after a fast launch.

In my opinion, after launch hard at 1st Shift, the car already had the momentum, so the higher 2nd Gear ratio(1:45)will force car move more faster (compare to lower 2nd Gear ratio(1:54))

Otherwise(when the car has momentum)lower 2nd Gear ratio(1.54) will hold the engine revving at high RPM but not really good for acceleration.

Posted By: forphorty

Re: Low FIRST Gear 904 transmission - 09/16/10 01:10 AM

they use the 1.54 with the 2.74 low so the rpm won't drop so much on the 1-2 shift. The rpm drop on the 2-3 shift will be slightly greater with the 1.54, compared to the 1.45. It's all a compromise.Just run the 2.74, 1.54 gearset and don't worry about it.