Build your own diesel RV

[Sasquatch]

What was the donor rig for the Allison transmission?

It looks as though the transmission has an output shaft parking brake, is that right? (If so, it would make a swap easier for me if I could somehow remedy the generator issue.)

Have you figured out gear ratios yet? Will the stock rear end ratios in your coach be fine as to not let the diesel over rev?

[Superhawk]

Subscribed ! Good luck with the conversion - Im watching this closely... post up pics regularly :)

[Tweaker]

I have that exact same motor home with 28,000 mi. I don't feel it is underpowered and get 10-11 at 65mph on flat ground. Not enough experience to get the real average, but I do use it in mountains where it lives.
If yours is an '88, I would really like to buy your catalytic converter if you have one. Then I will need advice on why my cat plugged with low mileage.

[NomadRip]

[pilo]

Crazy project...I love it.

[Joz]

Thanks for all the feedback. That's a big part of the reason I've posted it up on here.

The oil pan depth is a concern. If it won't fit as is then hopefully it will fit if I pull the oil pan then reinstall it once the engine is in. Obviously I'd rather not do that.

I intend to use new but the same motor mounts as were in the Dodge. I expect to have to fabricate mounting plates but I'm pretty optimistic about the fitment. We'll see.

Converting the generator to propane is much lower on the priority list but I have to agree - I don't want to be carrying 3 types of fuel but I'll just run it on unleaded for a while. I don't use the generator enough to really be concerned about it burning too much propane. The little Honda portable units are a great option if it comes to that but I do want to be able to run the AC in the dead heat of summer.

Good points on the Dynamat type insulation. I'd like to do that but time and budget will dictate when that happens.


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It probably doesn't look like much but I just received a cable operated shift modulator for the Allison today. Courtesy of 4btswaps.



Yes, I should already know the rear end ratio but I don't. I'll figure that out when I get it on a hard surface (much easier to jack than on recycled asphalt). I'll swap the diff if I have to but hope to run it as is. For some reason I think the axle is a Dana 80 but I could be totally wrong. I've tried looking up the numbers a few times and just got frustrated. The donor truck had a posi 3.55. That would have been nice to keep but pulling the differential would have made the truck immobile and I needed it gone. That's about the only thing I would have liked to keep.

I got distracted tonight by rebuilding USD Showa forks for my CRM and working on pannier mounts for my Africa Twin. Lots of fun!

[VxZeroKnots]

Originally Posted by Joz

Yes, I should already know the rear end ratio but I don't. I'll figure that out when I get it on a hard surface (much easier to jack than on recycled asphalt). I'll swap the diff if I have to but hope to run it as is. For some reason I think the axle is a Dana 80 but I could be totally wrong. I've tried looking up the numbers a few times and just got frustrated. The donor truck had a posi 3.55. That would have been nice to keep but pulling the differential would have made the truck immobile and I needed it gone. That's about the only thing I would have liked to keep.

I got distracted tonight by rebuilding USD Showa forks for my CRM and working on pannier mounts for my Africa Twin. Lots of fun!

just a decent picture of the pumpkin and a hub and i figure out what it is. if it is a D80 you have nothing to worry about.

if your rear hub more resembles this:
(note the external retainer bolt patter withing the studs)


than this:



then you should be fine weight and torque wise.

[Joz]

All right ZeroKnots, I'll take you up on your offer. I think the last time I went looking for numbers on the axle I must have been blind (or maybe it was December and FREEZING). No matter, there's tons of numbers all over the axle.

Here, we see "70" and "70-1SU" on the pumpkin:



Bottom of the axle tube:


Rear of the diff:


Useful numbers stamped on the diff cover:



And since you asked:




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So....I still need to figure out the ratio. If I'm to believe the diff cover stamp (13 -8) then I have 1.625:1 ratio. That doesn't make any sense, but if I multiply that by 2 then I get 3.25 gears (13/8*2). That sounds better but I don't think I should have to double the result. Maybe I shouldn't care about those numbers at all.

I also jacked up one wheel, marked the wheel & the drive shaft. Here's what I find:
- 1 rev of the tire = 1.75 revs of the drive shaft
- 1 rev of the drive shaft = .55(ish) revs of the tire

If I use my own measurements 1.75*2=3.50. Does that make sense?

Of course I could pull the differential cover and count gears but that's just too much of a mess.

Either 3.25:1 or 3.50:1 works for me.

[Nailhead]

Originally Posted by Joz

Rear of the diff:

In this photo, there is a tag protruding from between the cover and the casting at 5:00 from the filler plug. That should have the ratio stamped on it.

I can't see it clearly enough, but sure looks like the one that was on an old Dodge I had.

[Cbody]

Originally Posted by Nailhead

In this photo, there is a tag protruding from between the cover and the casting at 5:00 from the filler plug. That should have the ratio stamped on it.

I can't see it clearly enough, but sure looks like the one that was on an old Dodge I had.

The Ford dana/spicer 70 has the tag on the right side of the filler plug, it's attached with the two bolts directly to the right of the plug. It's a long plate, not a small tag like Dodge uses. The ford plate will have all the axle info along with the ratio.

[Nailhead]

Originally Posted by Cbody

The Ford dana/spicer 70 has the tag on the right side of the filler plug, it's attached with the two bolts directly to the right of the plug. It's a long plate, not a small tag like Dodge uses. The ford plate will have all the axle info along with the ratio.

It was a Dana axle, so I thought maybe that method of labeling was consistent through their product line, and whatever I see in that photo looks like an ID tag and is located where I remember mine was.

[VxZeroKnots]

that is a Dana 70, aside from the model being stamped on it, the thicker lip at the bottom of the diff cover differentiates it from a 60.

It should have 35 spline shafts and the 10.5" ring gear is more the adequate for the cummins engine. being a full floater you don't have much to worry about, I wouldn't think.

the tag held on by the cover bolts should have your ratio, 3.55 sounds about right though given the application.

here is a ton of good info on 70's but be wary of posting newb questions on pirate.

http://www1.pirate4x4.com/forum/showthread.php?t=522333

[Joz]

Thanks guys! Sure enough - under a sheet of slobber was the ratio: 3.54. Right there the whole time. I just didn't know where to look.

At this point I'm satisfied with the ratio. No need to mess with it when it will handle the power and the ratio will push me down the road just fine.

C'mon delivery man! Bring my engine parts!

[Dieseldoc]

As a retired diesel mechanic, and lover of all things diesel, I applaud your ambitious project.
I've seen pictures of the B-series Cummins in a Ranger, with a 10 speed Roadranger trans, so I'm sure the E-350 will handle it.
My big question is, where are you going to put your feet? That Cummins is a good sized lump and those engine rooms are pretty tight with the 460 or 7.2 diesel. Will you have to modify the engine cover or make a new one? How about the firewall? Is the Allison going to clear the floor, or will you have to cut it?
Not trying to rain on your parade, but as someone that's performed a lot of engine conversions these things come to mind.
It seems like a 7.2 or early model Powerstroke would be a lot easier to swap in.
Good luck with your project, seriously. This will be a fun one to keep up with.
I was given a 6hp Yanmar air-cooled diesel. Right now I'm trying to fit it on my edger! Kind of a Tim Taylor thing.

[Range Motorsport]

3.55 is the smallest ratio you would want. 3.73 or 4.10 would be better for hauling heavy loads so I wouldn't recommend towing anything too large with it.

The D70 axle is good up to 8000lb/ft of torque and came stock behind the Cummins for many years.