[JonnyB]

First off i'm new to the site and i'm loving it already. I have a 89 stang with 4.10 gears. I heard its not the best idea to drive a car with those gears on the interstate so I was thinking of getting 3.73 gears. Any particular brand I should look for, and how hard is the swap? Also my center consoul is broke, any good site to order interior parts from?

[Drick]

Welcome to the site

3.73 would not be much different on the express way than 4.10s. They would only run probly a couple hundred rpm different. If you want to run on the interstate alot go with 3.25s or something high like that but if your not worried about mpg on the interstate dont even make the swap. But if you do plan on making the swap go for ford racing they make good gears along with richmond. The swap souldnt be done unless you really no what your doing because there is alot to know about it.

For the center console check with late model restoration supply (50resto)

[Drick]

Also is it an automatic or a 5-speed that would make a difference too.

[JonnyB]

Its an automatic. I don't really do a lot of interstate driving its just my uncles shop I planned on storing the car at during the winter is a about 70 miles out of the town i live in. What would a safe rpm range be for that long a drive?

[Drick]

Just a guess but I would say you will probly run a little over 2500 RMP at 70 75 but then about 3000 at 80 that would be fine for 70 miles just take it slow at 70 and theres nothin to worry about

I have 3.73s with a 5-speed and run a little under 2500 rmp at 70 and a little under 3000 at 80 so theres not that big of a difference. But your may rev a little higher because you have an auto but not enough to hurt t on the interstate. I drive to indianapolis sometime from were I live and its 8 hours from here and my car is fine

[Tony_90fox]

Keep the 4:10s in there! Dont swap out for 3:73s. I wouldnt do the swap if you havent done a ring and pinion before, but if you can afford to mess up, go for it.

Interior parts, 50resto is good.

[TurboLX]

www.50resto.com

[neverfastenough1]

86gt is right. Less than two hundred rpm difference. I'd be more worried about making sure the speedo was a close as possible to correct. Especially for interstate driving, so you don't get a ticket. Your aod has a higher gear ratio (.66) in overdrive than the t5 (.67). That will be less rpms right there.

[JonnyB]

Thanks for the advice. My speedo is of by 10mph, is there a way to correct that? Also I found that going 60mph has my car running at 3000rpm and 65mph at 3500rpm.

[neverfastenough1]

Good news and bad news. Good news... you have an 89 with a 7 tooth drive gear. Bad news... even with the biggest driven gear, a 23 tooth, you still would be off a little. Even worse news.... the 23 tooth gear is so thin they wear out and strip easily. You can figure out what rpm you should be at by...

RPM = MPH x GEAR RATIO x 336 / TIRE DIAMETER

MPH = RPM x TIRE DIAMETER / GEAR RATIO x 336

[86GT50]

Dont Change to the 4.10's, you will regret it..........

[usmcsawgunner]

86GT50 is def right...you will prolly feel a loss in the "throw you back in your seat" power...im gettin 4.30 put in and i have a t5 and im really not worried about it...if you have overheating issues you might want to get that looked at but 70 miles really isnt that bad anyway...def stick with the 4.10s

[neverfastenough1]

There is a company that makes adapters to correct speedos. You just send them the info and they will make an adapter to correct whatever gear ratio you want. They are however not cheap, although if you want to keep your miles close to correct for resale value it would be worth it. They run like 150 or something. I'll find it if you are interested, but if you are not foreseeing selling it, I would just do the formula to figure out what speed you are doing at certain rpms and call it a day, and enjoy the 4.10's.

[nolife]

Sorry to highjack the thread but what about a speedo gear for a 3.73 with a .82 5th gear? I know it sounds odd but based on much testing, calculations, my GPS, pacing with another car, and using mile markers for many miles on the interstate, I believe I have a .80-.82 5th gear in my T5. The dead give away is I can be 3000 in 4th and after immediately shifting to 5th, I am at ~2400. Well, either that or I do not have a 1:1 4th gear which would be really odd. My speedometer reads about 10mph high at 60-70. I wish I knew what was done to my T5 before i bought the car because I have found no rebuilders that use a .82 5th in a T5 other then some people suggest it for road racing use.

[JBIGBOOTSY]

Originally Posted by nolife Sorry to highjack the thread but what about a speedo gear for a 3.73 with a .82 5th gear? I know it sounds odd but based on much testing, calculations, my GPS, pacing with another car, and using mile markers for many miles on the interstate, I believe I have a .80-.82 5th gear in my T5. The dead give away is I can be 3000 in 4th and after immediately shifting to 5th, I am at ~2400. Well, either that or I do not have a 1:1 4th gear which would be really odd. My speedometer reads about 10mph high at 60-70. I wish I knew what was done to my T5 before i bought the car because I have found no rebuilders that use a .82 5th in a T5 other then some people suggest it for road racing use.

well then it's junk... just sell it to me

[TaterTodd]

JonnyB, for parts you can check out MPS Auto Salvage -Mustang salvage, New and Used Mustang parts

[95StangMX]

Hopefully he got those parts by now, I am guessing so since that was like 3-4 years ago!!!

[flyin ryan]

Originally Posted by 95StangMX Hopefully he got those parts by now, I am guessing so since that was like 3-4 years ago!!!

LOL