I have seen one other truck that left the factory with different ratios. It was many years ago, but the owner purchased it new and found out the hard way. It can happen so don't give him too hard of a time. I have doubts also, but s**t happens.

There are other things that have left the factory over the years as bad or worse than this.

 

It should have been discovered during the dealers PDI
pre-delivery inspection.

This guys makes it sound like his is working fine.

 

2 different gear ratios can cause binding when in 4x4. We had a truck come in that a shop replaced the gears in the rear with 3.42's when they should have had 3.73. Customer was in the mountains and said that the 4x4 was binding real bad.
As far as the factory carrier locking up and then dragging a bit, Ive seen new truck do that. The clanking when going into gear also is normal to a point. A 4x4 has the Transfer case which has extra clearances that you wouldnt feel in a 4x2. Why are you wanting to drop down to a 3.90 gear? Not really that much difference than the 4.10.

 

although it's possible your truck came that way, i would highly doubt your transfer case and/or diffs would have survived this long. Your truck SHOULD have come with identical gearing, and DEFINATELY should be replaced with identical gearing, front to rear.

if you really want to know for sure, put your truck on jackstands, mark the driveshaft and a tire, and then rotate the tire until the driveshaft has rotated 360 degrees, while counting the number of times your tire rotates. that is your gear ratio. do this front and rear, and they should come out the same.

 

They are supposed to be within 3 point of each other (3.70-3.73, 4.09-4.11, etc.) Once you start getting past that, like some Fords with 3.50-3.55 you start having issues. My truck will drag or buck in 4wd on dry pavement when parking, and both ratios are the same. Most trucks with a viscous clutch in the t-case will do that because it acts like a posi between the front and rear diffs, and the front and rear tires are going different speeds.

 

Boy have I opened a can of worms. It seems now though, I`m getting some responses. I`m not trying to unnerve anyone here so don`t take offense anyone. I have been 4 wheeling my whole life. I have owned a 4x4 since I was 15. I`m 32 now. My 99 Chevy, though, has never seen the mud. I paid too damn much to stick that heavy a$$ land yahct in the mud. So, I`m a little rusty when it comes to dealing with 4wd`s. I got tired of working on muddy trucks. So, I decided to start messing with rusted out and caked in grime muscle cars. I`ll have to go check the numbers again on my truck, but when a friend of mine and I decoded the codes in the glove box, it stated I had a 4.10 in the front diff. My truck`s 4wd system has rarely been used except in ice and snow and the mud I encounter out on the construction job. Back in the day when I was out in the woods every night getting stuck every 10 feet I had alot of buddies that loved the mud as much as I did. It was a common thing for someone to have taller gears in the front axle than the rear out there and those trucks always survived. Anyways, I appreciate the responses guys.

 

See what the tag code says and then count the teeth on the R&P and divied thoses #s,You said you have it a part and snapped the reverse thread bolts,if those wont come out of the ring gear with ease then you will be looking for a new set,you will then need to press off the pinion bearing to get the shim out to reuse or install new that is the same thinkness,seems most OE 10bolts are .035,Had you been on here earlier and asked what people here like for these 8.6 diffs most would have said eaton.

 

My memory has came back to me about building a rearend when I realized that I stripped the bolts on the old ring and pinion. I am familiar with setting a rearend, just rusty. I have a factory eaton posi in my 67 camaro and love it. I went with the Truetrac because I have firsthand knowledge of them from using one in my last chevy z71. As much as I like the eaton, I like the truetrac even more. For anyone that`s not familiar with them, they have no clutches to wear out in them or no week spider gears. They have worm gears located at the end of the axle that actuates the posi and locks the wheels. They are extremely quiet, require no use of limited slip additives and I have seen them listed as bomb proof. I have NEVER seen one broken out on the trails. That is how I was turned on to them. Can anyone tell me what the RPM difference is between the 4.10`s and 3.90`s? I do alot of driving in my truck and drive long distances in it almost daily, so I need to be able to get the best gas mileage as I can. The 3.73`s though are just not working for me anymore. My power level went down and gas mileage went down when I installed the 285`s on my truck. I`ll post the numbers from my truck to you all and make sure I`m correct about having split front and rear ratios as soon as I can. Thanks again