1985 Mallard motorhome conversion

[KRoberts]

Sorry I haven't posted anything for nearly a year, but my Mallard motorhome conversion is nearly done, so here's an update. I bought a Cummins engine and 47re automatic transmission from a '96 Dodge 2500 2wd and swapped it into an '85 Mallard Class C motorhome, built on the Dodge 1 ton truck, not van, chassis. I used the '96 intercooler and '92 motor mounts and radiator, '92 front coil springs, along with a modified original rear crossmember, and a modified drive shaft made up from '92 and '85 parts. I had to move the center portion of the grill forward 1 1/2" or so (from flush mounted to surface mounted) to clear the air conditioner and oil cooler radiators, and I had to raise the transmission hump an inch for clearance. I used the '96 PCM computer and wiring harness, trimming off a lot of unneeded '96 wiring and joining the '85 and '96 wiring at the ignition switch. I was able to transplant the '96 factory cruise control and also the '96 brake lite switch. I used the '96 cruise control button panel, a '92 instrument panel w/ electronic speedometer, a '92 message panel (wait-to-start, etc) , and the '96 overdrive on/off switch. I added a 2" Isspro tach and an extra lite for the "Gen" indicator. Everything went surprisingly well, considering the huge amount of work and opportunities for things to go wrong. It runs like a top and has very good accelleration with the 4. 56 gears from the 360 V8 still in place. It runs about 1900 RPM at 55 MPH with 30" tires. I'm taking it on a trip soon to check out the fuel economy, I expect I may need to swap out the 4. 56 gears for 3. 56 or 3. 7 ('96 truck had 3. 56). I have a couple of questions yet:



1) Does anyone know if the speedometer gear from the 727 transmission in the '85 will work in '96 47re?



2) Is there any chance the single wheel axle from the '96 would work in the '85, with added spacers for the dual wheels? It's possible there's considerable difference in width from the pickup to the LWB cab and chassis frame that the motorhome was built on.



Thanks for your help, I'll report back on my fuel mileage, and maybe I can help with questions you might have if you're thinking about a similar project.



Ken

 

[Applegator]

Wondering if you have Dodge coined wheels on your motor home? We did a similiar conversion putting a 92 D-250 cab/engine onto a 83 D-350 Dodge frame (165" WB). We converted the 92 single rear wheel to dual using the 83 Dodge dually wheels. We also wanted the 3:54 gear. We have put 20K on the truck with no problems so far.

Fred

 

[KRoberts]

At the moment I have 16" wheels and new tires on the dual rear wheels, and the original 16. 5 " wheels and tires on the front. I got 6 16" wheels from a '92 Dodge dually in the wrecking yard. We have a '92 2500 4X4 that we bought new and the rear end in it looks the same as the one the '96 that I got my engine and transmission from. I looked at it and measured it, it's narrower between backing plates and the spring perches are closer together than the '85 motorhome. I does look like the brakes are at least as big, though. My '92 has the 3. 5 gears and that's what I'm looking for, too. The local shop quoted me $800. 00 or so to change my 4. 56 gears to new 3. 5's, if I remove and re-install the rear end for them. There's a charge included for the new carrier that's needed to change from 4. 56 to below 4. 1, on a Dana 70 axle.



Thanks



Ken

 

[Applegator]

We think the 92 wheels you got from the wrecking yard are the right wheels. You may also have coined wheels on the Motor home. Coined wheels have a small lip at each stud hole. There a 4 lips on the inside and 4 on the outside of the wheel. The coined surface is what centers the wheel on the axel. The rear brake drum and the front rotor are also coined. The 96 axel is not coined. The first thing to check is whether the the 92 inside dual will clear the 96 axel brake drum. Then, if this is OK, since the 96 axel is narrower than the motor home axel, determine if you have tire clearance inside the motor home wheel well area.



We buy from the wrecking yards too and we have learned that some of their wheels are bent. You should check for that. The studs on the motor home are probably 5/8's and the 96 axel are 9/16's. That's not a problem. We measured the spring perches on the 92 D-250, the 83 D-350 and a 97 2500 and they are all 43. 5 inches center to center. Your 96 axel should be that measurement. We hope your motor home is that measurement too.

 

[KRoberts]

Vacation Trip Update

Well, I just returned from a 1500 mile vacation trip down the West Virginia Turnpike, through the Smoky Mountains to Stone Mtn, Ga. and back up through Tennessee and Kentucky to Ohio. I worked out the odometer correction factor from the mile markers ( I still have the speedo gear for the 3. 56 gears), it came to . 76 (. 76 times indicated = actual miles) . I checked the mileage at every fillup, filling to the very top, and I averaged 16. 5 MPG for the entire trip! I got the motorhome weighed at a feed mill and it weighs 9300 lbs, so the Cummins is doing a phenomenal job. This was at 55 mph max with the original 4. 56 gearing, so I'm going to forget about changing the axle ratio for now; I doubt if it'd pay for itself and I want to tow a car occasionally, anyway. Everything worked super including the cruise control.



Ken