I looked for a posi set up for my truck a couple months ago on the net. I found a couple places that can hook you up but you will pay alot.

 

hey-Hey!!!,
The Dana Powr-Lok was an option. I found a 3.07 rear with one ov these in it and rebuilt it; new clutches for the posi, new bearings and sand-blast/powder coat, and a set of SpeediSleeves to fix the wrecked-by-rust seal journals. With an NV5600 ahead of it the 1990 is a mile-eater; no more hunting for another gear on the highway...
cheers,
Douglas

 

got them in my 90. if i tow i lock out the od which works great. IF i need to move a large load i just use low range in the transfer case. always been one that liked to tow in 3rd gear and use od for unloaded driving. less monkey motion and heat build up in the trans.

 

I have been toying with the idea of 3.54's in my rig (727 with a gear vendors) I like the mileage empty at 75, however, towing here in Commiefornia is limited to 55. I tow at 60 or so, and its almost lugging at that speed (almost). I would really like to install a 47RH as the lock up converter would really help, then if I kept my gear vendors it would be a double overdrive!
I would then be able to install 4.10's.

 

91 W250 w/ 727 & 3.07's

 

I think I would like to swap out to 3.07's. I got a call from Hamilton(?) Cams a couple days ago, he told me that to get my peak torque down as low as possible, to call Colt Cams. I want to keep my 2500 redline, but run a tighter converter. THat or just stick a gear vendors in it with what I got. My top end shows just over 75, which would put me about 82-83, with it showing about 5% slow. Maybe I've got something faster than 3.54s already?

 

The 90 listed in your sig should have 3:07's. All nonIC auto trucks had 3:07's.

When the OD auto's came out in 91.5. The 3:07's started going out of production. Dodge didn't see a need anymore for them with an OD auto.

 

where do i find the tags on the axles to tell me the gearing, im sure i dont have3.07's in it? Th PO of my truck said that the axle was changed out at one point

 

The Tag will be on the left side of the rear cover under 2 of the cover bolts.

and yes a Lock-rite will slide right into a 3.07 rear.....the Lock-rite is pretty much the same thing as a powertrax. They're both made by Richmond. I know a guy that has 2 3.07 trucks both with lockrite rears

 

hey-Hey!!!,
The best way to find the axle ratio is to jack up the rear wheels and count turns of driveshaft and wheels. If you've got an open, just jack up one and multiply driveshaft turns/wheel turns by two.
cheers,
Douglas

 

I'm wondering what sort of mileage increase I would get by changing from 3.54 to 3.07??? it's a big jump in rpm.

 

3.07 Divided by 3.54 = .867

The 3.07 will require about 87% of the 3.54's Driveshaft RPM to move the same distance...Or 13% less which ever way you want to figure it.

Will it save you 13% on fuel? Not likely. Probably somewhere around 8-10% on the highway. So you might go from 20MPG to 21.8 or 22MPG.