4 wheel drive loud popping (Kapow!) noise 91 S10

My 91 S10 blazer has been making a loud popping noise whenever I have it in four wheel drive and going up a steep hunting trail or fairly steep dirt bank. I had the Transmission fluid changed last week and they topped off the front differential with about 1/2 quart of 90wt gear oil. (front axle seal leaks 1/2 quart/6months). I put the vehicle trough a series of steep pulls in 4 wheel drive and I was excited that the problem was finally fixed by the Transmission fluid change. WRONG! Went hunting today and the same old popping sound happens. its like you go about 5 or 10 feet then Kapow! sounds like something just broke... then proceed another few feet and Kapow again!

This is driving me nuts! I seem to remember each time I add gear oil to the front differential the loud Kapow! goes away for awhile. I just dont see how there could be a connection between low differential fluid and this loud pop. Anyone out there have any idea of what could be causing this.. I'm afraid something is really going to let go when I'm way back in the "boonies"

I would check my CV joints, had the same noise a few years ago on an S10 and sure enough CV joint...good luck

My 91 S10 blazer has been making a loud popping noise whenever I have it in four wheel drive and going up a steep hunting trail or fairly steep dirt bank. I had the Transmission fluid changed last week and they topped off the front differential with about 1/2 quart of 90wt gear oil. (front axle seal leaks 1/2 quart/6months). I put the vehicle trough a series of steep pulls in 4 wheel drive and I was excited that the problem was finally fixed by the Transmission fluid change. WRONG! Went hunting today and the same old popping sound happens. its like you go about 5 or 10 feet then Kapow! sounds like something just broke... then proceed another few feet and Kapow again!

This is driving me nuts! I seem to remember each time I add gear oil to the front differential the loud Kapow! goes away for awhile. I just dont see how there could be a connection between low differential fluid and this loud pop. Anyone out there have any idea of what could be causing this.. I'm afraid something is really going to let go when I'm way back in the "boonies"

Well I agree it could be the CV joints in some instanses like if you are turning. (I have never heard of a CV joint making noise driving straight ahead; you usually have to be turning while putting power to the drivetrain...<meaning accelerating>)

You should have the transfer case checked. Sounds like the chain in the transfer case is slipping... Just heard one here recently and it sounds the same way. Here's what you can do to check for sure... Put vehicle in 4x4. Press and hold brake FIRMLY (Do not let the vehicle move) then steadily press the accelerator peddal and see if you can replicate the problem while it is sitting still...(You might have to apply alot of accelerator to replicate the sound...)

Either that, or check the tire sizes from the front to rear. Make SURE THEY ARE THE SAME SIZE tires. It is critical on a 4x4 otherwise it will cause the 4x4 system to "bind up". (You probably already know that); Or also check to make sure the gear ratio in the differentials is the same from front to back...(This will also cause "binding".)

I messed up with my explaination above...

You need to accelerate hard, but apply the brake just enough to let the vehicle move but not quickly; My uncle (who is a mechanic) said it had to move alittle to see if the chain is slipping...

I messed up with my explaination above...

You need to accelerate hard, but apply the brake just enough to let the vehicle move but not quickly; My uncle (who is a mechanic) said it had to move alittle to see if the chain is slipping...

Well today I had a hunting trip planned. I thought it would be a good idea to just check the oil in the front differential. I did and it was low... I noticed the seal was leaking pretty good on the passenger side front axle. I thought I would try to thicken my differntial oil with some good STP. Heated it up and poured in about 6 ounces. Took it for a test ride and run the ole girl up some pretty steep banks........... no popping no Kapow! just ran slick as a whistle....... guess I need to get the seals replaced, but I just can't see the relationship between the low oil and the popping unless the thing is bone dry! (which it wasnt.

I messed up with my explaination above...

You need to accelerate hard, but apply the brake just enough to let the vehicle move but not quickly; My uncle (who is a mechanic) said it had to move alittle to see if the chain is slipping...

Glad to hear you got it fixed. I just replaced my driver-side axle seal as well. They're a pain to get to, or at least mine was. I am planning to replace all the seals like that under-neith. They are all a little wet...