Yeah I saw some neat options for the d80. But I'm just trying to stay in the practical range, especially since I'm out in the hill country. Prices don't seem as bad as I thought, but it's still some good amount of change for one swap job. If I can get away with doing it myself, I'm looking pretty good. I did confirm that the split point is 3.73 down and 4.10 up like Tate mentioned. I'm going to make a phone call and see if I can get an out the door price to get everything I need to set mine up myself. The only thing I don't have is the spreader tool, which I'm not sure if it's critical or not. My neighbor might have one I can borrow if it's a must.

I also found out in some research that the nv4500 was supposedly designed to originally work best with a 3.54 gear ratio setup. Thought that was interesting...

 

The gear guys I deal with say a spreader is rarely needed on the D80. I've pulled and installed carriers in D80's and never needed one either. A small pry bar and you roll the carrier out from the pinion gear and it just falls out.

Jeff

 

Never a problem towing with mine.. A few power tweeks made it more reasonable accelerating through the 3-4 shift. But after that I rarely pulled it out of OD pulling about 8K Lbs of TT. I still don't know why you would have to need the 4:10 unless you run up and down the coal mine mountains every day hauling rocks.

 

My dad and I made a case spreader for when I did the locker in my D44 years back. Two pieces of square tubing, 1/4" bolt through it to act as the pins, and two pieces of 3/4" all thread to jack them apart. I needed to use c-clamps to hold it to the diff, but it worked well. Makes it easier to install a diff with proper amount of preload, especially when one bearing has a air fitting and a rotating seal on it (ARB).

 

Thanks again for the replies guys. Haven't had a chance to figure out a final cost yet. But I just found out I had a bad ball joint and possibly tie rods. But I'm still going to do this gear swap. I'll order parts pieces at a time if I have too. I'll give an update when I find our some more info on parts.

 

3.55?!? I hate this gear ratio! IF you have a manual transmission it might be good, but sucks with an automatic! I want more accelerator response off of the line, and towing was better with my Duramax 3.73 with 285's. My truck not only tows sluggishly, my EGT's clime quickly after a few minutes, and the torque is not there! I like knowing that if I want to pass a semi towing 10K I know I can. But, with 3.55's and now 305's, not a chance! I get about 16-17 mixed driving, 18-21 freeway, and could definitely trade gears and still find the sweet RPM range to get great gas mileage. From my research, I have found rear gears partnered with appropriate transmission changes are essential. With 3.73 or 3.90 you can maintain towing ability and freeway MPG depending on MOD's.


The 3.55's do not challenge the diesel engine enough to benefit the high gear ratio. The RPM's should be higher when driving. This is just my take.

 

These things ain't V-8's............. If you have issues with sluggishness, look at your Automatic and TC.

Believe me, 3.54's are the sweet spot gears for a Cummins.

We can light the Turbo way quicker than the Dmax or Pchoke guys.........

 

While that is nice in theory, the front pumpkin is on the wrong side. Tcase would have to be changed for sure, and the front axle would have to be modified for the coil springs and suspension attachments.
I am sure it is doable, but definitely not a bolt in.

 

With a diesel you don't want high rpms. You want your desired speed to match up in the 1700-1900 rpm range.
If you don't like the way it accelerates, then take off the monster 305's. I have 3.55 & 245/75/16's, & she spools up very nicely. If you want the big tires, get a truck with 4.10's & you should be just right.
I put 235/85/16's on the back to help lower rpms, but its still 2000-2100 at 73-75 mph. Too high for me; I'd like to find a 3.23 axle for my 2wd.

 

You sure about that? Displacement and heads that flow well do wonders for lighting a turbo, and the Cummins isn't known for either.


Or just swap the pumpkins between axles, so you have the D61 on the newer suspension. Drill out the plug welds, press out the old tubes, press in the new ones, reweld the plugs, bolt it in.

 

Hello again, just an update. I ended up selling the 96 4wd 3500 for an 02 2wd 2500 auto. I really didn't want to sell the dually, but after going through all I would have to do, in the end I could of just bought a newer truck how I wanted it, and that's what I did. The 2500 has a 3.55 and I love it. However, I would have been happier with a manual. As someone mentioned earlier, 3.55's with the auto just seems a little to much for when hauling. I think having the wider gears with the manual would be perfect. I had a hard time pulling 5k through the hill country, which was to be expected with this option. The reason I went for an auto was because a family member can't drive stick and she's the only one with an auto. So we were tired of the issues that would arise when she needed to drive another vehicle other than her own. But like I said, overall we'er happy with the new truck. Anyone can use it when they need to. I don't plan on hauling anything heavier than 6k since I don't have a gooseneck anymore. Anyway, just thought I throw this up for yall!