I presently have a 350 with a richmond 4 speed transmission. My rearend gears are 3.08. If I were to change to a 3.55 or 3.73 what kind of e.t. improvement can I expect to get? I am presently running 14.30s. BTW I have a 10 bolt in it right now. It is a 3600lb 66 chevelle. I know I ask alot of questions on here but I am trying to learn as I go and you guys are a great resource! Thanks to you all.

What was your best ET and what is your average?


I'll guess 2-3 tenths easy,more with tuning

With the deeper rear gears you would have more torque multiplication and could see the gains Chris mentioned on a theoretical basis.

But you could have trouble with hooking the car and therefore not gain very much or even lose a little depending on how you launch the car.

Will you feather it out of the hole a little bit more because of tire spin? or can your tires and suspension handle a harder hit and improved 60 ft times? If they can handle it, you will likley improve your ET .2 to .3.

You need to be able to launch the car as hard as you would under the 3.08's and with that I mean the car must be able to launch quicker with the new gears....Traction must be there.

I would guess you would still shift at the same RPM's assuming you have optimized your shift points with the current setup. RPM's would come back up quicker after shifts.

My best e.t is 14.33. I have only made a few runs on it though. It has gone about a tenth quicker each time I run and get more familiar with drag racing. the other runs were 14.54 and then 14.45, then came the 14.33. I launch at 4000-4500 right now with drag radials and get no wheel spin at all. 60ft times are 2.21-2.27. The car kinda falls on its face a little after launch and then picks up. That is why I figured I needed better gears.

I went from a 14.6 e.t. down to a 13.82 e.t. when I changed my 10 bolt from a 2.56 open rear to a 3.73 posi. And I have not really tuned my combo yet, so hopefully better numbers are coming. I think my gear jump is a little bigger than yours, but maybe you will have similar results. I have a 350 engine with a 350 trans in a 3600 lb car.

Originally posted by oregonchevelle+:
My best e.t is 14.33. I have only made a few runs on it though. It has gone about a tenth quicker each time I run and get more familiar with drag racing. the other runs were 14.54 and then 14.45, then came the 14.33. I launch at 4000-4500 right now with drag radials and get no wheel spin at all. 60ft times are 2.21-2.27. The car kinda falls on its face a little after launch and then picks up. That is why I figured I needed better gears. That's the info I needed..
Yes, they will definetly help

What is your 1/4 mile mph ?????

My quartermile mile per hour is 98.

Thats good for High 13's ....Good Luck

With a 98 MPH trap speed low 14s would be more common than high 13s. The gears will probably give you a couple of tenths with sufficient traction. This isn't too bad for a 350 in a 3600 pound car. Is that total weight with the driver included? I almost forgot to ask if the rear end is a posi-trac or not. With such a high rear end gear and a relatively small motor you may get more improvement.

Yes it is a posi unit and 3600 is with me in it and about 1/2 tank of gas.

Where do you race at?

I go out to White City. I have only been there on three fridays. I just got the car in August. I see you are from GP too! Nice Chevelle BTW. Mine is not a strip only car but more of a cruise car and occassional trip to the track.

Thanks. I'll probably see you out at Southern Oregon Dragway this summer. I'll be out there with a red (faded paint) '78 Malibu.

I still say expect a high 13 with your 98 mph speed which will likely increase to 99 or so when you lose that "fall on the face" after the launch. Most 13.75 to 14.10 cars I know run 99 to 97 mph. with 1.95 to 2.1 60 fts.

Thanks Tom, I hope to get into the 13s. I will look for you this summer Sean. I will be in the red 66 chevelle.

I would have thought the change of gears would give more than 2-3 tenths in the quarter. Not speaking from experience, but just trying to figure why he wouldn't gain more. Does the increase in torque mainly improve the 60 ft. time only ? Just curious.

Originally posted by BigBlockBeaumont:
I would have thought the change of gears would give more than 2-3 tenths in the quarter. Not speaking from experience, but just trying to figure why he wouldn't gain more. Does the increase in torque mainly improve the 60 ft. time only ? Just curious. The improvement would/could be more dramatic if he were using an automatic. The fact that he has a lower first gear than an auto and can already get the RPMS up quicker helps to reduce the benefit from the rear gears.

I would venture to say that the improvement would be greater if he had an auto because he would likely be running slower with an automatic and those rear gears.

Another way to say it is that it seems having the 4 speed is making up for a little ET lost by having such a high rear gear.

Oregonchevelle, What gear ratios does your transmission contain, ( first, second and third)? There should be a tag somewhere on the case giving the gear set code. If this transmission has a high first gear, (2.20 or so), you may well gain 3-5 tenths. Bogging the engine with street tires is kinda unusual even with high gears.

I was on BFG 275 60 15 drag radials. Regular street tires just spun. I have called richmond and emailed them with the numbers I found but they do not list them on there web site. Transmission may be older? It is a Richmond though. I just am having no luck finding out from them what the gears would be.