What Axle is under a 91 Oshkosh?

[daddywinz]

just bought a 1991 34' Safari Kenya with an Oshkosh chassis under it.
- Oshkosh probably built it in 1990
- Ford 460 with a C6 tranny (no overdrive)
- running 22.5 wheels
- I believe it's got a 4.56 ring & pinion in the rear end

I'd like to know the make of the rear axle. I don't take possession of it for at least another month (seller is still living in it), so I can't just crawl under it.

planning a diesel conversion, so i'm going to start looking for a cheap set of freeway gears to keep the diesel spinning slower. if it's just a dana 80, it'd be easy, but if it's something else....

thanks, fellow RVers
kevin

[jmerritt]

Contact Freightliner since they bought the Oshkosh/John Deere Chassis.
They should be able to give you the specs for that MH.
800.385.4357

John

[daddywinz]

nope, freightliner said all they could pull up is a couple of miscellaneous frame or brake parts. a very sketchy and short list, unlike when I had IH pull up the build sheet for my donor bus.

so, i'm looking for someone who's had or worked on a late 80s or early 90s Ford powered Oshkosh chassis. I really just need to know what the rear axle is. I don't know, but I would guess that a Chevy 454/TH400 combo would have the same rear axle. ...so long as they're of similar length to my 34 footer. Beaver too? my Safari is basically an off-shoot of Beaver, and may have used the same suppliers/parts.

thanks, all

[rsflight]

You can look at the info & manuals I posted here. I'm not sure if the info you want is there or not, but it's worth a look.

[jmerritt]

Kevin,

I have the same powertrain on a 88 John Deere chassis which was eventually sold to Oshkosh. It has a Dana HD70 rear axle with a 4.56 ratio if this helps. Also, you might try Colaw Salvage 877.548.2125 they probably could tell you.

John

[Mr. Hipster]

Diesel engine will be what??

[daddywinz]

i've already secured an international dt466; an indestructible 7.6L inline 6. it's backed by an Allison MT643 4 speed, non-overdrive.

the gas Ford 460 is pushing a non-overdrive also, with a 2.46 first gear. i figure with nearly twice the torque, and a 3.58 first gear in the Allison, i should be able to drop the rear axle ratio from 4.56 to something like 3.73. i'd go to 3.54, but i'm afraid to give away too much torque. i guess i'll be satisfied with going 65mph.

by the way, after looking into the Dana HD70 and Dana 80, it's likely that my 1990 Chassis got the Dana 80. they started using the 80 in '89, so i'm hoping it's got the beefier axle. either way, the R&P are going to be cheaper than the heavier bus axles.

[Mr. Hipster]

I see the sig line now. From a rat motor to a 6.2, interesting, it usually goes the other way.

[Argosy]

P30's of that era used a GM built axle.

If you search on 1990 F53 axle parts it shows Dana 80. If you have a donor bus why not use that axle?

Have you stopped to figure the actual torque out of the rear axles with the two engines? Once the axle ratios are factored in it's not as much difference as most people expect. And it's lot of work and expense to replace a gas engine with a diesel.

[daddywinz]

thanks. i'm convinced that it's most likely a DANA 80, not the HD70. the use of the 80 began in '89. it would possibly be the "make or break" difference, ...literally. i'm not sure the smaller R&P would give me the peace of mind i'd like.

the axle under the donor is a dana w230, which is incredibly expensive to acquire parts for. the 80 is cheaper all around, even for a freeway-ratio-carrier replacement.

diesel engine transplants aren't much worse than a simple rebuild r&r, especially when it's an all mechanical unit like my swap. the axle ratio, however, MUST be changed out to get cruise rpms where a diesel is happy. with a double-overdrive Allison i wouldn't worry, but the mt643 is a 1:1 4th.

i'm going to finish the swap, and drive it, but i'll likely be going with 3.73s in leiu of the 4.56s, giving me the ability to do more than 55-60mph. the international dt466 is often governed at 2400rpm!!!

i'll make the low cost of a dana 80 ratio swap back in fuel savings within the first few tanks of diesel.

[Mr. Hipster]

Originally Posted by daddywinz

thanks. i'm convinced that it's most likely a DANA 80, not the HD70. the use of the 80 began in '89. it would possibly be the "make or break" difference, ...literally. i'm not sure the smaller R&P would give me the peace of mind i'd like.

the axle under the donor is a dana w230, which is incredibly expensive to acquire parts for. the 80 is cheaper all around, even for a freeway-ratio-carrier replacement.

diesel engine transplants aren't much worse than a simple rebuild r&r, especially when it's an all mechanical unit like my swap. the axle ratio, however, MUST be changed out to get cruise rpms where a diesel is happy. with a double-overdrive Allison i wouldn't worry, but the mt643 is a 1:1 4th.

i'm going to finish the swap, and drive it, but i'll likely be going with 3.73s in leiu of the 4.56s, giving me the ability to do more than 55-60mph. the international dt466 is often governed at 2400rpm!!!

i'll make the low cost of a dana 80 ratio swap back in fuel savings within the first few tanks of diesel.

Running a 5.3 rear ratio w/44" dia. tires on my Wanderlodge with a 3208 and a MD 3060 Allison. 80 mph @ 2000 in 6th gear. If you want to consider that option for your DT engine PM me @ mhohnstein@wi.rr.com

[daddywinz]

thanks for that. i'd love to hit those numbers. that math shows that your functional tire size is about 42". about right, with squish.

in any case, with my 37" tires and 1:1 final drive (yours is a .65 overdrive), that rpm scenario would put me at a 2.89 axle ratio!!! i wish i knew what that'd do to my takeoff ability. i think, instead, i'll just have to live with a 70mph top speed and more like 2400rpms. seems like there's more hills than flats, anyways.

i can live with that. i'm not sure i wanna deal with an electronic tranny. i'll be cool with this coach for a few years, and as the kids get older we'll consider getting into something else.

[Manuel B]

When I called Freightliner at 1-800-FTL-HELP about my '90 Oshkosh MC-18FG chassis they gave me all the part numbers and info from the VIN, very, very nice people, went out of their way to help, some items did not show up on their computer, so they said they would have to dig through the books, they called me back the next day with the part numbers.

[Dave78Chief]

Parts manual for the JD Series (800, 1000, 1200) chassis

http://jdpc.deere.com/jdpc/pdfs/PC2109.pdf

You can map which axle applies to which chassis including gear ratio with it.

Dave