4.10 Gear Question

THE BIRDMAN

Registered User
I'm gonna do a gear swap soon and was thinking of goin with 4.10's over 3.73's so what's ya'll input.Also how can you get you're speedo to read correct after a 4.10 gear swap?My car is a 91 auto with 275/40/17 on 17x9 rims.I know you can swap out the little plastic gear inside the tranny but I've been searching and I only see ones that correct for 3.73's I'm sure they have to make one but I must be missing it.Also does anyone see any adverse affects of running 4.10's because my understanding is the aod doesn't have the output shaft bearing problem like the 4r70 and yes I know my gas mileage will drop but this isn't my daily driver I just figure these heavy cars could use all the gear I can throw at it to get it rollin.So am I missing anything?All input and opions will be appreciated.

Thanks Jay:D
 
Come on guys I know some of you are running 410's .What are you're rpm's on the highway I'm not to worried about it just curious it can't be any worse than my last 2 cars with 410's and no overdrive LOL.

Jay
 
I am going to run 4.10 gear also but I don't know about the speedometer issue. I think you'll run about 500 rpm higher than with 3.27's.
 
Search around on 4.10 and gear. There are some good posts in the member area and older days. this has been discussed quite a bit in the past.
 
You can put a speedo gear in the tranny for 4.10s, but it wears out in about 500 miles (teeth too small). There used to be a company that made an electronic device that changed the signal, but they are no longer making the part that worked on an SC. Cyberdyne Speedometer Calibration Box Part # 9902

I've heard that there are other companies out there who make a similar product, I just don't know who they are. This link contains a little info about it and the various speedo gears.

http://www.sccoa.com/faq/speedgr.html

David
 
You have to change the drive and driven gear if im correct. If you have a 2007 FRPP catalog check out page 139....im not sure if it applies to Thunderbirds though..but i dont see why not
 
4:10 gears seem pretty steep. I run 3:73 and have traction problems. Some people have gone to 4:10 and switched back to 3:73, why I dont know.
 
You can put a speedo gear in the tranny for 4.10s, but it wears out in about 500 miles (teeth too small). There used to be a company that made an electronic device that changed the signal, but they are no longer making the part that worked on an SC. Cyberdyne Speedometer Calibration Box Part # 9902

I've heard that there are other companies out there who make a similar product, I just don't know who they are. This link contains a little info about it and the various speedo gears.

http://www.sccoa.com/faq/speedgr.html

David

As David has said you can replace the speedo gear with the 23 tooth gear however as David has also indicated they don't hold up very well. I put the 23 tooth gear in my trans whenever I installed the 4.10s in my car and after about 10,000 miles it was definately worn out. Whenever I installed the 03 model trans in my car I had to install a Speed Cal unit from Dallas Mustang Parts along with the stock speedo gear to get proper speedometer readings.

The 4.10's are definately a good choice for a car with the engine being anything from stock to fairly highly modded but they will limit quarter mile speed to around 120 with an engine that is capable of around 6600 to 6800 rpm so if you intend to run more MPH then definately go 3.73's.

Charles
 
Thanks for the info.Yeah I wish I had the problem of having to switch to 373's because I was trapping over 120 LOL.My goal is to have an SC that will run 12's at any temps.So I figured 410's might help this and I only like to mod each item 1 time if at all possible.Speaking of that what do you guys think of this combo?MPX,15%over,85tb,85maf,3.5 intake,50lb's,2200 stall(lentech non lockup),shift kit,ported manifolds,full exhaust,and of course a Dave Dalke tune.Will this get me in the 12's or am I gonna have to do heads and cams too?

Thanks Jay


Oh also forgot 255 pump and double ic w/fan.
 
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