All things being the same if a guy was to install a low gear set in the 727 trans what could he expect to gain ??
How much would it change the 60' or ET ??
Looking to improve my 60' between this and/or a rearend gear change to get it done. I don't have a lot more rpm to use before the stripe, 500 to 700 rpm or so.
What would be some suggestions to accomplish this ??
Already had 2 different conv in it and still was the same.
Its a street/strip car so that is why I thought the trans over the rear gear. I like the idea of the 11.50 class but I need more ET to make it possible.
Thanks Guys, David

I guess you guys might need more info.
3700 lb car, J conv in it now, 1.68 60' now, foot break car,
leaf springs, dana 60 so gear changes aren't easy,
car runs 12.0's in decent air so I need half a second roughly.
I thought about installing some ported heads as another option.
Thanks, David

To go from 12.0 to 11.50 with what you have, you need to cut 3/10ths off the 60ft. No gear or converter change is going to net that. You need POWER

Yes more power and to be competitive in an 11.50 class you should in reality be capable of running 11.40s. My car 60fts in the the low 1.50s a few years ago we tried a low first gear set in my 904 and there was no improvement in 60ft or e.t. But that could just be my combination.

Just crunched some numbers here and came up with>

@423hp/3700
60 Foot E.T. : 1.67
1/8 Mile E.T. : 7.57
1/8 Mile Trap Speed : 89.76
1/4 Mile E.T. : 12.00
1/4 Mile Trap Speed : 112

@493hp/3700=
60 Foot E.T. : 1.59
1/8 Mile E.T. : 7.20
1/8 Mile Trap Speed : 94.46
1/4 Mile E.T. : 11.40
1/4 Mile Trap Speed : 117

So around 70hp more is needed, depending on what you have now and how you run it...ported heads/cam/carb improvements would certainly help towards that and then perhaps a look at the l/spring & shock set up depending on results...my2c.

I found little to no difference when installed in my 3800lb RR.

The cost of what a new low gear for a 727 goes for will be a good start towards a 904 with a low gear + longer driveshaft. (Selling the 727 related stuff will also help.) Back in the '70's, Chrysler did a lot of trans testing and the results showed that with all else being equal, a 904 was .15 faster than a 727 due to less rotating weight. Then you have the added benefit of the available 2.74 low gears from later 904s. The results will vary based on weight, rear gears and torque curves. I believe that a lighter car with a bigger engine/longer stroke will benefit less than a heavier car with a smaller engine/shorter stroke. A low gear in my 360 dart helped a bit, but it weighs well over 3,500 lbs.

(But if it's a big block, the 904 suggestion is not applicable.)


A online calculator could show how much more gear you can get by with - at least a step or two.

Also remember that the suspension and tires will also have to handle the extra torque multiplication from more gear and power.
Were the tires hooking the same with the converter comparison?

Accelerator pump tuning can help with 60' as well, which "might" need adjusting with gear/converter changes.

Give us your engine combo. You might find something that will get you closer to your goal.

Sure the 904 option is available for a big block.... just like my buddy's stocker wagon with a Pro Flight (not cheap... not even close to cheap).

If you saw no gain or loss in the last 1/8 mile on the converter change I would look at your fuel system to make sure I had enough volume to be able to jet it up enough to slow the MPH down in the 1/4 mile first
Me thinks something is keeping the car back from going faster

I didn't think that the engine might be a big block till after I posted. Then had to edit it just in case. But a cheaper alternative to a ProFlight (custom 904 guts in a 727 case for those who don't know) would be a JW Ultrabell to mate the 904 to the big block. The 904 would just need to be built well, not with all the custom & billet parts.

I know that this is not apples to apples but I started out with a low gear set in my car origionally and it was suggested to me to put a stock gear set in, glad I did car picked up almost 2 tenths in my 60 foot, my combo just did not like the low gear.

Wouldn't a really dialed in torque converter be the way to go? In a stockish low hp application I could see it making an improvement (the low gear set, reason it was originally made), but a dialed in high stall would make a low gear set have a negligible effect.

The quickest way to turn a 12.00 street car into an 11.50 index racer is a small N20 plate system.

My Belvedere's best pass N/A is 12.43-109, runs 11.50-120 on the spray.
We have two different promoters who do an 11.50 class, and it's been a blast.


Fin angle on a J converter wouldn't allow for any gains if you switched to a low gear set.

Thanks for the info guys. The car is raced by the woman and no NOS for it as the parts are just not that good and I don't trust her. Lol
The motor is a basic 440, trw piston 9-1 comp pump gas, 557 lift area solid flat tappet isky cam, (Don't have the card handy), 906 heads gasket matched and blended, stock valve sizes, torquer 2 intake, 950 holley. stock stroke crank etc. The fuel pump is a magna fuel 250 I believe, it worked good when we ran 10.80's. The engine was a throw together with what I had after we dropped a valve on the good motor.
The motor made 500 hp at 5600 rpm and 496 trq on the engine dyno.
Sounds like most cases the low gear set didn't show a big enough improvement for the cost and the work involved. It sounds like the best route for me is probably to install my set of ported heads. They flow 290 @ 600 so I am sure that is a huge improvement over mine now. I just got a pair of adjustable rear shocks also to try. So between the heads, shocks, and I can reinstall the domi if needed I should be Good.
Traction didn't seem to be an issue and if it does I will get some slicks to use.
How does this sound to you guys ??? I am thinking the heads alone should get me the 11.50's easy.
Anymore suggestions would be considered. Thanks Guys for the Help and Info. David

The heads should be a significant improvement. Maybe a 1.6 intake rocker. I'm questioning if your intake manifold is your best choice for your new combo.

I ran the old Mopar 2.77 helical cut gear set in my 727 in my B/SA one year and then sold that car after the last race.
I had done the math on the starting line ratio in 1st gear(2.45x4.89=11.98 compared to 2.77x4.56=12.63) and swapped the rear gears out from 4.89 to 4.56 and put a different fresh motor in the car, it ran its fastest ever with those parts
That was on new 9x30x15 bias ply slicks mounted on 10 inch wide rims, the car didn't have a traction problem before or after but it did run its best ET and MPH with that set up
On your deal I would swap them in in a heartbeat

I would go with that,.....my old Cuda ran 11.2 with a stock 440-6 motor with single plane intake/850DP and a big solid cam, fitted some BV 906's template ported to probably nowhere near the 290cfm that you have, it went 10.7 first run with no other changes. Probably could've tweaked that for a high 10.5 or 6's. According to the Wallace calc the heads were a 64hp increase.

A low first gear gives you a quicker reving engine
in LOW gear.. so you make it quicker to the
torque range of the engine... then you shift
earlier and have to have TORQUE to pull longer
in high gear.. it MAY not change the rpm of the
run... a gear change changes the whole run which
is a multiplier
EDIT
Bottom line is always... HP to weight ratio..
then make it efficient

With your heavy car, that torker II should be swapped out for a Performer RPM, for sure IMO. Ive tried them both on a Much lighter car and the RPM, was way better. It should be even More so on a car as heavy as yours.