My 1990 automatic 4.3L S10 changes into 4th gear at 40mph. But I rode with a co-worker the other day, who has an 1989 automatic 4.3L, and his doesn't change into 4th until 50mph. I found that his is geared higher than mine; engine doesn't rev up as high at highway speeds. [b]Can the speed in which a truck changes into 4th (or whatever the highest gear may be) be used to determined how it is geared?

if you wanna know the gear, its in the glove box, it should be a G something number

I've looked but I don't see it... I'll look again.

Is there a way to have the gearing changed for highway speeds? If so, about how much will it cost?

there should be a sticker on the bottum of your glove box, and to change the gearing you 'simply' do a rear end swap

there should be a sticker on the bottum of your glove box, and to change the gearing you 'simply' do a rear end swap

If he has 2wd... If he has 4wd then he's gonna have to regear the front too or the second he goes into 4wd it will blow..

^^^ thank you rlith, and sorry du, the possibility of 4wd slipped my mind when i said that

It's a 2wd. How much will it cost? And what should I tell the mechanic when I take it to the shop? Also, how long will it be in the shop? :confused: :)

tell the shop you want better gas mileage with a rear end swap, guestemate of 5-600 on price (guess on salvage yard and r and r) once started shouldnt take more then a day and a half at most, and please dont insault the shop by bringing your own parts, its like bringing your own eggs and bacon to a cafe' and asking them to cook it for you

there should be a sticker on the bottum of your glove box, and to change the gearing you 'simply' do a rear end swap

When I open the glovebox, I see a sticker that says "Service Parts Identifacation" on top and below it are a bunch of numbers and letters that has 3 letters/digits on each one; too complicated for me. :confused:

I did see one that said GU6, but it may not be the thing I'm looking for.

GU6 means you have a 3:42 rear

Thanks. So, is my truck geared pretty low, or is it pretty high? Is there a link to a website so I can compare and see which ratio I want so I can tell the mechanic?

3:42 is the best combination for on and off road driving as well as gas consumption..If you're looking for faster low-end speed look to 3:73 or over 4:

if you only have 4 gears, your best bet is to find a 4 speed with o/D, but as Rlith says 3:42is your best all around gearing

its an automatic, the older ones only have 4 gears and 4th is overdrive. gear ratios are weird if youre not sure how they work. 3.42 means the driveshaft turns 3.42 times to the tires turning over once. you can also look at it another way. you can use it as a multiplication factor based on engine power. so 3.42x(whatever the 4.3 torque is, ill guess)200ftlbs=684ftlbs driving the rear wheels. now before you go crazy thats not a lot compared to other vehicles. so anyway, using your imagination you can readily figure out that a 4.00:1 ratio turns the driveshaft faster in relation to wheel speed at lets say 60mph than 3.42:1. which means that youre multiplying the torque more, youre up to 800ftlbs now. However youve lost top speed and your rpms are higher. now if you go to a lower number the reverse happens. usually gear ratios dont go much lower than 2.73ish:1 and dont usually go much higher than 3.73:1 for good streetability. now for track use its different. if you get a whole rear end out of another truck you shouldnt have much trouble other than the speedo will need to be recalibrated.