408/ 904 trans

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o1heavy

1974 dart sport
Joined
Jan 7, 2009
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tarkington
Thinking of replacing the 727 with a cope 904 simply for the E.T gains
But a little concerned about the low first gear
Will it still help with a stroker
I have 456 in the Dana with a 28 inch
Almost feel like I may be using to much reduction when coupled with the low first gear with the 904
Any insight would be appreciated
Thanks guys
Engine
Basic 408
Should make 560-590hp
 
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Wouldnt use a low gear with a 4 inch arm. Not needed.
More for stock stroke heavier or lower powered car.
 
I have heard of folks picking up 1-3 tenths swapping to a 904. The low 1st gear may give you traction issues with a 28" tire...not sure...maybe others will chime in.
 



416ci, cope 904 with 5500 stall converter. Foot break with the low gear set works great with 4.10 gear and 275/60 tire. This is my friends Car
 
Sure it will usually “work”..... but why. If your making serious steam the low gear can and will make hooking on a marginal track more difficult. Something a points racer type person doesnt need or want.
It also widens the band between first and second gear. Some cars may not like that, compared to a stock gear spread.
Like i posted earlier, if you have a lower powered car, low gear can help get the car moving, same with a heavier type car with moderate power.
If car is light, makes a bunch of power, or both, generally the benefit is staying with a stock gearset
Low gearset is a bandaid.
I was tickled to find the trick Cope 904 tranny i bought on here isnt a low gear setup.
 
Sure it will usually “work”..... but why. If your making serious steam the low gear can and will make hooking on a marginal track more difficult. Something a points racer type person doesnt need or want.
It also widens the band between first and second gear. Some cars may not like that, compared to a stock gear spread.
Like i posted earlier, if you have a lower powered car, low gear can help get the car moving, same with a heavier type car with moderate power.
If car is light, makes a bunch of power, or both, generally the benefit is staying with a stock gearset
Low gearset is a bandaid.
I was tickled to find the trick Cope 904 tranny i bought on here isnt a low gear setup.


I agree with most of this. The biggest issue I think isn't the lower overall first but the bigger gap between 1st and 2nd gear. It will show up even worse if the converter is a bit tight. You can always clean up the low gear hit with chassis and shock settings but like B3422 says it may not like the extra gap between gears.

You can also run first out a few hundred RPM higher, but if you are already at the end of the power curve and the cam takes a dive it may not like first gear RPM extended either.

Depends on set up.
 
I run a 2.45 1st gear in our 71 dart with the 410 in it....would not use a low gear set in a light weight car with 4 inch stroke....this car needs a new converter...running a 1983 Turbo Action 3800 series ...probably flashing around 5k....but i think it has too much slippage...but its too hot to change it out....winter project.

Have used the 2.74 gear in a couple of 360s....but they never made much of a difference.....light cars with 5000+ converter and gears....save your money...
 
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I had some similar concerns we had the low set in our 340/904 set up ran well,built the stroker and bolted the same trans up to it with our 28x10 and the thing is hooking so far but only had 4.30 8 3/4 too much rpm through trap switched to 4.10,3450lbs with driver,don't think we are making your numbers in hp 10.66 best so far 1.42 60' with a little too loose imo 8" race converter.
 
I run a 2.45 1st gear in our 71 dart with the 4.10 in it....would not use a low gear set in a light weight car with 4 inch stroke....this car needs a new converter...running a 1983 Turbo Action 3800 series ...probably flashing around 5k....but i think it has too much slippage...but its too hot to change it out....winter project.

Have used the 2.74 gear in a couple of 360s....but they never made much of a difference.....light cars with 5000+ converter and gears....save your money...
guys thanks for all the input
I have to spend just trying to spend wisely
And most of you have more experience then myself
I’ve always been a test and tuner
This is my first attempt to actually race
Gonna try and compete locally in a 7.0 index
We have 3 tracks within an hour of us that will keep us. Busy
The 60’s are important to me
Again thanks
Ha but still haven’t made up my mind
 
If consistent 60 foots are important, keep the stock gearset. Much easier to keep consistent
Way more than the tranny gearset involved in how a car 60 foots.
 
If consistent 60 foots are important, keep the stock gearset. Much easier to keep consistent
Way more than the tranny gearset involved in how a car 60 foots.
Consistent and fast is what I’m aiming for
As are most folks I suppose
 
After talking with Dave at pro trans
Looks like the 904 with a low gear set is what I’ll be using
Hopefully I can get the Caltrac’s to do there thing
 
Lancaster, California. Dave Smith. Did/ does a ton of SS/ AH tranny stuff
Him and Rick Allison at A&A are actually in cahoots on a lot of stuff. Believe the brakes they sell, both had a hand in designing
 
Pro Trans is a very LARGE supplier of 727/904 trans for Stock and Super Stockers....
 
I’m gonna use his experience
And try the low gear set
Side note
He is moving his company and family (I'm assuming)
To Texas in the next few months
Happy to have him Especially being a Mopar guy
 
My 408. And my 904. Yes the 2 work together. No issues.

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A stroker makes a lot of TQ. Unless you need to run a specific time, like an index, that 2.74 gear isn't necessary. Racing on the street, marginal track or just a hot track and that bigger gear leads to traction issues. Pro Trans have all the trick parts for Mopars. Their full race trannys are 5K. What's your goal and use?
 
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I’m hoping the 28/10.5’s and the Caltrac’s will hook
If need be I’ll use a 10.5w plenty of room for more tire
I really don’t think the engine will be making the power it should but we will certainly see
Most of the time slips I see with a combo close to mine are in the low 500 range
But the “dyno” says 600
And if it doesn’t work I will get back on here and let y’all say I told you so
Worst case I’ll go back to the standard first gear ratio Just gotta try Dave seems to think it will fly
 
I think you'll find on tracks with poor prep the car will have start line issues. On a good track it will work fine. My car has a 530ish HP motor, 5800K converter, low first gear 904, 4.56 gear, and 28x10.5 tire. It will 60 in the 1.39-1.4 range on a good track, but on a crap track it will 60 in the 1.5+ range. The high and rear location of the instant center of the A body rear suspension leads to a violent hit at launch which is compounded by a high start line gear ratio.
 
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