Will this 4 speed trans fit in my '98 B1500 with a V6 if I use the correct (or a shortened) driveshaft? I would love to get an OD top gear into my gas-guzzling van.

 

I don't think the V-6's have enough torque for the OD tranny's. I have not seen a Dodge Van with the 3.9 and OD tranny. I think your engine would be working to hard while in OD and there by make the MPG suffer even worse.

 

My research indicates it will bolt up. Be sure to use the torque converter, dipstick tube and shifter cable bracket that goes to the 46RE. Not sure which flexplate to use but probably the one you already have.

However, I too am concerned about the 3.9L having enough torque to move a loaded van with OD engaged. Maybe you could look into swapping both the motor and transmission? My 5.2L makes over 300hp and 380lbs torque and still gets very good gas mileage. I do recommend getting rid of the thermostatic fan clutch .

 

My thought was to rig an O/D switch on the dash like on the older vans. This way, I could choose to engage top gear only when I'm on a section of flat highway where the 3.9 could benefit from running at lower RPM.

 

I did a little more research today and I believe your current transmission is a 32RH. My manual says that this transmission is not electronic. So what I don't know is wether or not your van would have the needed connectors that presumably hook the 46RE up to the PCM. I found this link which seems to indicate that a 518 would do what you want.

http://www.transmissioncenter.net/SwapInformation.htm

I found this Dodge transmission information elsewhere and thought I'd repost it here. The first digit is the number of speeds. 3 is 3 speed, 4 is 4 speed, 5 for 5 speed. The second digit is the duty rating of the transmission. the lower the number (0), the lighter the duty. The higher number the stronger the tranny is. The scale is progressive. Ram 1500s have a 46RE, while 2500 and 3500s use a 47RE. The "R" means rear wheel drive. The "E" stands for electronic while H is obviously hydraulic. So this would seem to imply that a 32RH is not a heavy duty transmission.

A heavier duty transmission uses heavier parts and has more reciprocating weight (ineritia). This means it will last longer but is less efficient and on its own it will probably lower your gas mileage. The question is wether or not the overdrive will raise efficiency enough to make up for that loss plus some. If the vehicle is light enough, I would guess that adding overdrive should be good for 2 mpg at highway speeds. But given that more power is now needed to propel the vehicle from a dead stop I can't help but wonder if your in-town gas milage would suffer.

Dodge automatic transmissions are not my strongest subject so if anyone has specific knowledge to add here, I know we would welcome it.

 

A 46RE would need a PCM to control the shifting. A 46RH would be the ideal hookup.

Even with OD, many of the Ram Vans have 3.92 rears. I would like to find a 3.23'ish with 8-lug wheels to swap for better MPG.

 

I was just thinking that too. The ('94 and up) Dodge 5.2L vans I have come across seem to have 3.5 rear gears and 5.9L vans all have 3.9 gears. Not sure what gearing they used on the 3.9L versions but the two I looked at both had the light duty 8 1/4" rear end.

Taller tires would allow you to test the concept to some degree.

 

The HD 3/4-ton and the 1-ton vans from 1998-2003 have the Chrysler Corporate 9 rears. Would like to know if it's possible to change out the gears or rear on the van to be better for MPG. The 5.2L towing is already overkill for my towing needs already. So, a better ratio in the back for MPG wouldn't hurt my towing needs.

 

I don't think that would be hard to find this differential with 3.5 gears and just swap rear ends. The lug bolt pattern is only designated by the hub on the axle shafts. These shafts are held by clips and from looking at the diagrams you can probably just swap axle shafts if you need a different bolt pattern. You may want to find out if the axle shaft spline count is the same as yours first. On a Ford 9" there are 3 possible spline counts.

My 2000 Ram 1500 conversion van,(5.2L, 46RE ) has the 9" Chrysler corporate rear end with 3.5 gearing. I made sure when I bought it because I personally would not trust the 8 1/4" to live for long on a truck.

 

I have had three 3.9L vans and all have had 8.25" rears with 3.55 (DMD) gears.