1988 Chevy k1500 4x4 5 speed need to know what gear ratio the rear end is. Says on the ring gear 3984831 12-41 G.M.K.

SOURCE: 1998 chevy k1500 4x4 4

first of all your truck is already in first gear when your going down the road....lol

SOURCE: rear end gear ratio

you can count the teeth on the ring gear and divide that # by the tooth count on the pinion. An example is: ring gear 100, pinion 10 ...100divided by 10 is 10, expressed as 10 to one. (fake #) your diff is likely a 3 series such as 3.23 to 1. or a four series such as 4.11 to 1. If you have four wheel drive it is critical to match exactly. if not you can get better performance by changing ratio to something that better fits your needs. 4 series pull loads well, 3 series are better on fuel.(depending upon terrain)

SOURCE: I have a 1994 chevy k1500 4x4 and need to change pitman arm

Take the bolts out that attach the steering box to the frame and pivot the box so you can fit the puller on.
Leave the steering shaft and power steering hoses attached.
Mark the new pitman arm and old one in the same place and mark the pitman shaft to keep the same position of the new pit man arm on the old shaft as the old pitman arm.

SOURCE: what is the gear ratio in a 1993 Chevy 1500 with

A 10 bolt differential case has a 8.5 ring gear . A 14bolt has 2 different covers one is a 9.5 the other is a 10.5 .

SOURCE: How do I replace the ring gear and pinion in my 68 Camaro 12 bolt

You can change the ratio back to 4.10. However, if you do not already have the specialty tools required to do the job, you will likely be better off finding a shop that will change the gears for you. A mistake as simple as incorrect backlash will result in destroyed ring & pinion gears.

Your cheaper options will be :
1. Find a matching rear-end with 4.10 gears and swap it in.
2. Purchase the ring and pinion, master install kit, and find a friend that has installed gears before to help you out.
3. Find a 4x4, Hotrod or auto shop that is will swap the gears for you. If the axle is in the car, it's usually more expensive than if you carried the axle in for them to work on.
4. Purchase R&P, Master install kit, all the required tools. Then hit the books to find the proper procedure and measurements for that axle.

Good Luck.

Testimonial: "Thank You very much for the info. I thought you could just change the gears without any other adjustments."