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michigandon, Just my opinion of course but in my mind you should swap out the rear axle in that thing. I don't see any reason for your gearing and the benefit of milage and speed not to mention your hearing :) will be greatly appreciated by you. I would seriously be on the prowl for an axle to swap in there. Either a D70 or a D80 in the 3.54 or 3.31 flavor respectively...
 

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I am looking at doing a 4BT in a short 19'-23' motor home.
As soon as the garage is built.
Any input on the idea?
By the way I LIKE the conversion :D
 

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I am looking at doing a 4BT in a short 19'-23' motor home.
As soon as the garage is built.
Any input on the idea?
By the way I LIKE the conversion :D
Same gearing opinion. Diesels do not have the get-up-and-go from a standing start issues the gasser counterparts do. The sweet spot is 1800-2200 rpm and the top rpm is +/- 2800. Big gearing (4.10 +) is counter productive IMO, unless your hauling an obscene illegal load up the mountains...

I personally look to OD transmission over a 3 speed 1:1 final drive and lockup torque converter would be the ultimate but not absolutely necessary, depends on budget and mechanical aptitude. And IMO 3.54 is plenty and readily available in both D70 and D80 axles.
 

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Discussion Starter · #5 · (Edited)
It has a D70HD in it. Pretty hard to find carriers for anything but 4:56 or lower, I'm afraid (I've looked). Also, swapping out the entire rear end would no doubt result in having to go to a different wheels (I don't know of anything else that had five-on 8.5 Budds on it). Keep in mind that the 8r19.5 tires are 33" tall and that I still have a .69:1 high gear with the 518. IMHO 3.54s or 3.31s would be wayyyyyyyyyyyyyyyyyy too tall when trying to move this 12,000lb+ beast off the line.

0-60 in 3.5 hrs perhaps? :eek:

I know of another conversion like this that has a 4:10 rear end and a lockup converter. He gets about 2-3MPG more than I do.

Ultimately, I would like to either located a "divorced"-type Gear Vendors ($$$$$) or an old Brownie (getting hard to come by) and mount it in place of the carrier bearing in the driveshaft. Hey, what's wrong with having your cake and eating it too? :dustin:
 

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...(I don't know of anything else that had five-on 8.5 Budds on it...
I haven't heard of 5 on 8.5 Budds. The 5 on 8 Budd pattern is common to older medium duty IHC and Dodge trucks. That also means that gear ratios like 3.54 are non-existant in the axles they used and the brakes are generally not that great. Here's a pic of my '60 IHC B140(the smallest med duty IH) with it's original axles that are 5 on 8 pattern, 6.17 r/p, wearing 9.00-20 tires.



Ken
 

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Discussion Starter · #7 ·
Of course you're correct Ken. I couldn't remember for sure if it was "5 on 8.5" or "5 on 8". I do know that it was once a very common pattern used by Ford/Dodge/Studebaker and many others back in the late '40s/early '50s.
 

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I didn't mean to be a smarta$$, was just curious. There's lots of unusual things around and I thought maybe it was another pattern. I certainly didn't know you didn't have some 5 on 8.5 Budds.

One thing I am very interested in is if the wheels on your motorhome are original or if you had some custom wheels made. I ask because I've not before seen a drop center wheel with the 5 on 8 lug pattern, only lockring wheels. Or are those lockring wheels? It's kinda hard to tell with the front covered by the wheelcover and on the rear the ring would be to the inside.

Very neat motorhome by the way.

Ken
 

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Class C motorhomes and engine clearance

I have been researching and lurking on these 4bt sites for over a year now, but have yet to contribute. My "dream conversion" is a Class C rv gvw 10k-12k loaded. I originally purchased a 24' model with a SBC 350 /TH400 wanting to swap the 4bt/TH400 from a dovebid purchase. I realize now that that is not a very practical swap unless I dont mind traveling at 50mph or less.
A 6bt /4l80 seems to me to better fit the bill. I'm aware of the gearing issues, but am concerned with clearance. I could modify the engine cover if needed. I dont see too many conversions in g30 or e350s vans. Any thoughts would be appreciated. E Anderson Chattanooga, TN
 
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