gear-tire-rpm

[Gearhead10]

Got a question. Im trying to decide what gear ratio I should run that works good with my stall converter. I got a 2200 rpm stall, 350 auto trans, 33" tall tires and want to run a 3.25 or 3.50 ratio gear. My goal is to be running above 2200 rpm at say 55-60 mph. I've looked at some rpm calculator on the internet but it dont compute out right. If someone has a formula or can direct me to one that would be great. Thanks

 

[jmlcolorado]

I'm going to subscribe to this one cause I'd like to hear the answers.
I'm working the other way around, looking for the right stall converter with about your same setup though I have 3.07 gears.

 

[donsrods]

My handy dandy gear ratio calculator tells me that at 60 mph to get 2200 rpms with a 33 inch tire you need a 3.6 to 1 ratio. Since that is not a popular ratioo, go with anything between 3.50 and 3.70. With those tall tires I would go 3.70 at least or it will be a slug out of the hole.

Don

 

[gold03]

There are online calculators for this. The only issue I see is the stall converter must be in lock up mode while at hi way speed. Make sure your engine RPM is high enough to lock up at speed.

gold03

 

[old man dave]

According to Randy's ring and pinion you will turning 2195 rpms at 60 mph. But I have to agree with Don run at least a 3.73 gear, that would put you at 2340 rpm.

 

[donsrods]

I always thought that you had to be running at the rpm where your convertor locked up, but I am not so sure any more. Both of my Sons are running 3000 stall convertors in their hot rods and they never seen 3000 going down the road, yet the convertors are definitely not slipping. So maybe stall speed does not relate to where a convertor is locked up under driving conditions.

Don

 

[gold03]

I suppose the issue around torque converter lock up/ slippage is related to load. Little load = little issue with heat?

It just would not be real efficient maybe.

gold03

 

[donsrods]

For sure you won't have any problems with a 2200 stall, that is not much over stock. The guys who run into problems are the ones running 4,000 rpm convertors and even then a good cooler will take care of that.

We switched my Son's out from a 2400 to a 3,000 and the only difference we can see is that it doesn't lurch when you put it in gear and it also pulls harder on acceleration. A lot of guys on the t bucket forums are running 3,500 stall convertors because of the light weight of the cars.

Don

 

[old man dave]

Also an engine that makes good torque at the stall speed will not slip. Where most people go wrong is putting a high stall converter behind an engine that does not have enough torque or gear to get it in the power band. A lot of variables such as cam, vehicle weight, how it will be used, size of carburetor, gear ratio all play a part in deciding what converter to use. Or just use what ever you can find cheap and see how it works.

 

[Gearhead10]

The guys at the shop where we hang out have said hiway speed should be slightly higher than torque converter lock up, which for me would be anything higher than 2200. I found this website last night www.offroaders.com/info/tech-corner/reading/mph-rpm-htm , look under tech section, calculators. They have formulas that according to it, Don is right a 3.70 or 3.73 would be right on. if I droped down 2 tire sizes a 3.50 would work. Either way I gotta buy a set of gears.