Mine was built with a 3.55. This replacement axle is a 3.92. Both have limited slip diffs.
I noticed years ago that the trucks equipped with the 20" wheel option usually had the 3.92 ratio.
Yesterday I took the truck to my axle guy.
I talked to my axle guy today about changing the gearing. He suggested to look for original Chrysler gears in the junkyards because the aftermarket stuff has been problematic. Noisy gears are common according to him and he said he can't guarantee any new set will be as quiet as a factory set. I found a yard that had 3 trucks with the 3.92 limited slip differentials. Their prices are great too. $170 for an axle complete with rotors and brake cables......Score!
I thought about just getting the cleanest one of the three and swapping it in junkyard fresh.
I have pretty good luck in many situations. THIS was one of them.
I had help today getting a rear axle out of a truck. For you east coast guys, you'd wig out at what we have out here. Clean, dry parts that barely need any help to remove. A few spritzes of PB Blaster and a short breaker bar and *CRACK* the nuts came loose. Hardware can usually be used again. Getting the axle out was easy. The truck had NO bed on it so access was great.
Then.....
These axles are heavy! I've pulled and bought several 8 1/4" and 8 3/4" axles and hauled them myself. I can lift and move them with a little bit of grunting. This is a 9 1/4" truck unit with rotors and calipers. The axle tubes are 3 1/2", maybe bigger. While loading, my buddy slipped and fell....injuring his knee. I had to take a board from the back of another truck and break it down for him to use as a crutch. I helped him out, loaded the tools and was aiming to just leave the axle where it was. It was on HIS wheelbarrow though. I helped him to the truck and put the tools away. On his insistence, I went back and wheeled the axle up to the building, paid for it and plan to return for it tomorrow. My buddy and I are even now....In 2016 I hurt my back helping him load a front and rear axle from a truck that he parted out!
The axle that I brought to my axle guy was a 2002 or 2003 that I pulled from a self serve junkyard here in CA.
I was tempted to just swap the entire axle myself since the inside looked fine and the gears felt nice and tight.
My axle guy said the differential case was wasted....it had started to grind away at the main caps. The ring and pinion were fine though since any shavings that were worn off got collected by the magnet in the housing.
He took the 3.92 gears and just swapped them to my axle in the truck. My differential was still fine. He says that many of these Dodge 9 1/4 axles with the limited slip differentials have that flaw where these bolts in the case that back out and grind away at the main caps. Even at 375,000 miles, mine is still tight and quiet.
The 3.92 gears are just as quiet. The low speed throttle response is better. It feels like I don't need as much throttle input to get it up to speed. It does accelerate faster at WOT.
The cruising rpms are not that much more than before. At 75, it was turning 2200. Before, it was around 2000.
The axle guy only charged $400 to inspect the donor and to swap the gears over.
If I would have just swapped the whole axle over myself, I would have had a bad differential, damaged housing and main caps and
still had to take it to the axle guy.