Converting 904 transmission to 2.74 low gear set

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ir3333

ir3333

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How many guys have made this conversion and how do you like it?
I just picked up a 904 with these mods.
 
It works well if your gears aren't too deep, normal street gears from 2.76 up to 3.55. I used it at the track with 26''tires and 4.30 gears and it really(in my case) didn't make a difference as I ran the standard 904 in one trans and a low gear set in another 904.Not only me, but others at the time stated the same results.All were track cars.Either way I wouldn't hesitate to use it.
 
Same here, I use to run a 727 which is 2.45. The damn thing was so violent out of the hole it would break wheelie bars. Switched to a 1.80 Power Glide and it was more consistent and a lot nicer to drive. This was in my 2615 lb 67 Super Gas Barracuda.
 
Using the 2.74 set in my barracuda street car, working well with 2.94 rear gear , turning around 2200 rpm at 65 mph.
 
ir3333 said:
Thanks for your input...exactly what i'm planning...2.94 rear gears.
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It will keep you sane when leaving the intersection, for the street with hwy gears coupled with a slant/2 brl 273 car... it helps for that.
I put one together for my 71 swinger 225 / with other hop ups.
 
The low gear set was designed when emissions equipment cut engine power severely. In other words it's for lower torque engines or as a compromise for tall gears, which I consider 2.94's to be. It'll be especially helpful if your running a small cid engine. If your running a torquey stroker it won't be as noticeable
 
Can't believe this has generated almost no interest.
Should be good for one size numerical lower rear gear and that's 'gotta be a bonus!
....unless you never drive on the highway?
 
I maybe late but I have the 2:74 gearset in my 904 behind a 340. The rear axle is a 3:55 with 26.5 tall tires.
I really think it helps the car get rolling much quicker. My set came out of a /6 truck trans because they needed as much help as they could get accelerating from a light or pulling a trailer.
In case you didn't know the low gearset is 1st and 2nd gear only. Third gear is still 1:1 so you get a noticeable drop in RPM shifting out of second into third. But if you have a torquey engine it's really not a problem.
 
lkopaska said:
Using the 2.74 set in my barracuda street car, working well with 2.94 rear gear , turning around 2200 rpm at 65 mph.
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With a lock up 904. Lucky dog! I had a tranny but scrapped it. :BangHead::BangHead::BangHead:
 
no..not a lock up.Just using the 1st and 2nd gears from a lock-up and installing in a regular 904.This also takes the planetary a 5 band assembly. Using this set with a 2.94 rear is like a regular trans with 3.30 rear.Using it with a 3.23 isn like a 3.6 rear through the 1st 2 gears
i know guys that have done this and don't notice the shift from 2nd to drive difference.
 
OK a regular 904 with a 2.45 first gear and a 3.23 rear gear is the nearly the same as a later 2.74 first gear and a 2.94 rear gear.
but the final drive ratio is 1:1
2.94 x 2.74 = 8.05 : 1
3.23 x 2.45 = 8.07 : 1
 
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actually i think i screwed that up, or at the very least it was too confusing....and have edited it to reflect just the first gear drive ratio.
' i'm gettin' old.
 
Older than you think...Cuz 3.23 X 2.45 does not = 8.07; it's 7.9135...otoh...3.30 X 2.45 = 8.0850..You were right the first time.
 
bobscuda67 said:
I maybe late but I have the 2:74 gearset in my 904 behind a 340. The rear axle is a 3:55 with 26.5 tall tires.
I really think it helps the car get rolling much quicker. My set came out of a /6 truck trans because they needed as much help as they could get accelerating from a light or pulling a trailer.
In case you didn't know the low gearset is 1st and 2nd gear only. Third gear is still 1:1 so you get a noticeable drop in RPM shifting out of second into third. But if you have a torquey engine it's really not a problem.
Click to expand...
not quite its 1st gear only. 2nd and 3rd are the same as any other 904/ that I do know for sure
This part Im not sure of but I thought tehy built some with the lower 2.74 and no lockup? I know the 2.74 1st gear variants were technically called a "998" and a "999", they werent called a "904" even though that's pretty much what they were.
I think I read somewhere the 998 was the low gear non LU, and the 999 was the LU version with the 2.74 1st gear. maybe one of the factory service manuals I have? Don't remember where that info came from.
 
1st and 2nd both have altered gear ratio,
Lower on both just not as much on 2nd than first.
998 vs 999 are due to engine torque load trans was built for.
Period!!!!

904. 2:45. 1:45 1-1
998 2:74. 1:54. 1-1
 
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I installed low gear sets in two mid 1970ish 904s. Both are used in bracket cars.
 
Yep, I replaced the 1-2 gears and the 3rd is still 1-1. When I did it years ago I was told you'll lose a lot more rpm on the 2-3 shift from the stock gearset, but it's not really that bad.
 
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