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gear ratio question 87 k10

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89k5350

1/2 ton status
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ok i bought a 1987 k10 stepside with stock 350tbi 6 months ago it has 4 inch tuff country lift and 35 inch tires and 700r4 tranny i put some miles on it for the first time this week cause i just turned 16 last week when i bought the truck i was told it had 3.08 gears and a tranny geard lower due to long gears and big tires but everyone says that there is no way the tranny was geared lower. i notice this truck kinda has balls for being what it is quarter throttle gets me accelerating pretty decent to 50-60 and from a dead stop and with out the brake when i mash the gas it will burn the 35s for bout 10 12 feet so judging by this what gears do you guys think it has?
 
probably 3.73's...kinda hard to guess given the description. My truck has 5.38's and cannot burn the tire 10-12 feet.
 
No one can say for sure what gears are inside, you need to figure it out by doing a little investigating. One way for the lazy ppl is to mark the drive shaft and with someone looking underneath, slowly drive forward. Count the number of revolutions the drive shaft makes with one revolution of the tire. Or the better way is to remove the dif cover and look at what is stamped on the gears. That way you can inspect the gears and also change the fluid. But by the sound of the way you're driving I wouldn't worry about it since you'll have to replace them soon.
 
Go here: http://brochures.slosh.com/ Should be able to find the brochure for that year. May not have your particular vehicles brochure, but should get you close. It will be under the drivetrain info (chart with engine, trans, etc).

By 1987 I'm fairly certain the 3.08's were much less common than they were back in the early 80's when overdrive auto trans started becoming more common, and prior to fuel injection. Fuel injection, coupled with the OD, obviously provided enough benefit that the gearing didn't have to be so terrible.

My guess is that if anything numerically lower than 3.73 was offered in 1987, it was less common than 3.73.

If the sticker is in the glovebox, what are the "G" codes? (Example: G80, GT4, etc) Things could have been changed since the truck was built, but without doing more work, that's the best idea you are going to get.
 
im just going to pull the cover like rampage said and look for the stamp but if its anything under 4:10 then im buying some new 4:56s
 
in both diffs, yep...
 
It's a little bit more in depth than just pulling the old ones out and new ones in. You have to reset the shims, drive easy and from what you said above that's going to be hard for you for the first 500-750 miles to break them in properly, change the fluid again and then it will be done.
 
its on the outside of the ring gear. Setting up gears is a pain if your not patient, or don't know what your doing. Imo, I wouln't regear some 1/2 tons, id just drop the tire size down or get some 3/4 tons that have atleast 4.10 gears in them already.
 
if you're lucky the tag will be on the outside of the carrier and still be readable and correct. but highly doubtful.
 
that tool kit is way to specific for not our size axles.

it takes lots of skill to correctly setup and get gears correct.

i have done a few and getting better at it but no pro at it yet.

need good selection of tool / pullers / shop press / parts washer cleaner / good lift or pull axle from vehicle as i wouldnt wana do it on the ground.

its not a beginer job for most people.

check what ya got first.

then we can make a informed decision from the info you find.
 
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