Arrrggggg! Rearend gear selection problems, advice?

[cjohnson1]

Crap, It's still not drivable. I did drive it out in the street one day, but found the brake master cylinder decided to resign from it's duties during the swap. It would have been nice if I'd gotten notice first. Didn't hit anything, Thank GOD!

So I set about getting a replacement. Not so easy. Nothing has been on this swap, so I wasn't surprised. My old MS had flair fitting built into it. Not so with the replacement. Adapters right?, WRONG! I found one for the little hole . 1/2 by 5/16th flair. But the bigger hole (#5?)does not have one for it, anywhere.

SO, what does this have to do with the rear end. Not a damn thing, other than I cannot remove the rear end until I get the brakes fixed. My big jack is tied up under the front axle. And the little floor jack won't pick up either end. So that's where I've been lately. Along with rearend nightmare.



Little airplanes are buzzing the field airstrip behind my house. I should have bought a plane instead of the motorhome. Cause then I would "have" to pay somebody to work on it, and I could spend all my time playing. Woops, sorry, I got distracted.



Ok, back to the subject.



Ya'll tell me if I'm outta my treehere. OK?

I have a 1850 rpm 5. 9 L diesel in place of the 4000 rpm Ford 460.

My transmission has 1:1 high gear still.

The tires are 33 inches tall when full of air.

The Dana 70HD rear end is geared with 4:88's.

This means that it's turning 3530 rpms at 70 mph with the 4:88's.

My Cummins is bumped up to about 250-260 horses. No idea what the torque is.

I'm not real crazy about buzzing the 5. 9 motor at 3530 rpm.

I'm thinking (correct me if I'm off base here) but I would like to be able to do 70 mph with this motor at about 1900 rpm.

This means that I'm needing about 2. 70 gears in that Dana 70. To achieve my desired goal. Not factoring in torque converter slip yet. But we're in the ball park.

Now for the hair pulling part.

The tallest gear I can find for the Dana 70 is 3. 54's which equates to 52 mph at my desired diesel cruising RPM.

Looks like I'm going to have to go to a different rear end.



Anybody out there have a suggestion for what rearend will fit dimensionally in the same space as the Dana 70HD? With a ratio in the 2. 70 - 2. 80 gear range. . And let's not forget I would like to retain my current monster disc brakes and wheels. There just isn't room in my motorhome to carry two different spares. OH and the drive axle is a dually too! Wheels are Aluminum 6 bolt 19. 5's RV type.



The Dana/Spicer has some new medium duty axles that have the ratios I need, but no info as to the dimension or price. I thought I'd ask here before I called their sales department. Besides my money tree has finished blooming. (For Now Anyway)



So ya'll kick this around for a while for me and feel free to offer up some suggestions. I'm out of my element here and having to ask to learn.



And if you read all this and want to comment,

Thanks!





Sorry for the NOVEL!



Curtis Johnson

 

[Brayden]

[cough]1000 SERIES[/cough]







You'd probably be money ahead if you were to go with the 1000 series now instead of all that rear end/gear work.



You could sell your AT, and all the adaptation parts that you have, and keep that rear end gear. .



With the overdrive of the 1000 series, you'd be moving 53. 2 mph @ 1850. Why don't you up the governor on your motor to 2500 or so? 2260 RPM would get you 65 mph. Then if you wanted more speed you could then change the rearend to 4. 10 or so. 4. 10's would get you 77 mph @ 2250rpm's. That's really nice IMO.



Did you get my PM?

 

[cjohnson1]

We gotta talk by phone one of these days!



I just read you PM.



I can work that out for you. I need to return the engine pallet to him one of these days. Havn't done it yet cause he's 70 miles from where I live now. But if I can killl two birds with one stone then it won't be so bad. So, yea I am planning to make a trip that way soon anyway.



I'm all for a 1000. I could even go ahead and put the 4:56 gear in the rear and hit the 1900rpm at 71mph.



But now I'm wondering, Am I trying to go too fast for the motor RPM? I need all the milage I can get, but still want to be able to do mountains towing my rock crawler.



Let me send you my cell # back on that PM. Give me a call or shoot me your # and a good time to call and we'll talk this out. I talk faster than I type. I've got a National Cell phone, so it won't hurt me to call you.



CJ

 

[backroad]

Oh Man do I feel for you on, nothing about this conversion has been easy. I constantly hear about some of the conversion guys saying how easy their swap has been. Why oh why, do I ALWAYS have to do things the hard way?



On your rear gear... 3. 08's ought to be available as they came in the first generation dana 70's before they went to an overdrive transmission. Just for a reference and according to my figuring, my Ford dually with the Cummins, running a 4. 10 gear, the 518 (built to run hard) converted to a lockup converter and 35/12. 50-16 tires, figures out to run about 1700 rpm @ 70. This was one of my early decisions to run the Dodge 518, just because it had the highest OD ratio and it really can be built as a tough transmission with all of the RACE stuff available for the 727.

 

[Philip]

On your rear gear... 3. 08's ought to be available as they came in the first generation dana 70's before they went to an overdrive transmission.

The 3:08 housings and carrier assy's are different from the 3:54 and higher gear set. So you can't do a fast gear swap.



You could get the 3:08's after the OD trans came out. My 93 has them in it.

 

[cjohnson1]

Originally posted by Philip

The 3:08 housings and carrier assy's are different from the 3:54 and higher gear set. So you can't do a fast gear swap.



You could get the 3:08's after the OD trans came out. My 93 has them in it.

Yep, the 3:08 would come awfully close, if they were still available.

The 3:54 is the tallest new gear available now. Unless somebody has a 3:08 gearset under their workbench. And Phillip is right about the carrier being different. I had already accepted that fact. But still there's nothing to work with. I think I'm going to try and find an Allison 2500. It's a 5 speed overdrive auto and will bolt in place of the AT 542 I believe. Plus it has a park pawl. I'm going to leave everthing as is until I can locate a 2500. Or something else. Then I'll gear the rear end to suit. Guess I'll be driving it home from the shop at night on the back roads, since it won't go more than 52 mph, geared the way it is. What a shame, the AT 542 is in such good shape. Unless I can find a Brownie Box somewhere. I'm still looking for any workable, affordable option.

Course, If I could fit some 44' tires back there my problems would be over.



As for the Master Cylinder,( Makes me think of Felix The Cat every time I say that word), I got it rebuilt. The original one! Took the day off to install it. Took all day to get it installed and bled. Funny, the brake bias valve was stuck too. Had to dissasemble it and clean it, to make it work again. The electric back up system came apart while messing with the Master cylinder. Boy, that was a mess. I had to take an extra long shower to get all the brake fluid and transmission fluid off me tonight. The shop floor will never get clean.

Small victories.



Now if I can find a way to up the gearing. Only need a . 71 to 1 overdrive. OR, a 2:70 final drive.



No other leaks at the moment.

Hope ya'll have a good weekend.

CJ



I'll be adding some pictures later tonight.

 

[keimmmo]

I pull a big travel trailer... different animal, but still a lot in common. For one thing, there are times when you will want the grunt of the low gears as well as wanting the high gears every time you hit the road. Have you considered something like the Gear Vendor overdrive? You could potentially have the best of both worlds! Just a thought.



Steve

 

[cjohnson1]

Originally posted by keimmmo

I pull a big travel trailer... different animal, but still a lot in common. For one thing, there are times when you will want the grunt of the low gears as well as wanting the high gears every time you hit the road. Have you considered something like the Gear Vendor overdrive? You could potentially have the best of both worlds! Just a thought.



Steve

A while back, had a very long talk with a Gear Vendors Engineer. They won't sell me one for the AT542 as the 4:1 reverse will break the housing if the throttle is applied too heavy. I even asked about signing a non liability letter if the housing were to split. He said NO!



I even asked about the possibilitiy of a divorced overdrive gear box in the future. Again, he said probably not enough strength to handle the reverse gear ration on that transmission. But they do have one on the drawing board. But not for my application. Guess I got too much motor! I dunno!!!!!!

ANybody knowanything different, speak up. (PLEASE!)



That would be the perfect set up. There was a Brownie box made years back. But parts to rebuild them don't exhist anymore. Oh sure, bearing are there but gears for them are out of production,.





CJ

 

[RobertMiller1]

OD Allison

Curtis,



Sure seems swapping out your allison for another model allison with OD and dropping to a 3. 73 or 3. 54 rear ratio would be the ideal setup for your van.



btw both of those gear selections will probably require a new carrier. Your's being a 4. 88



You would have enough bottom end grunt to pull most anything.



Can you sell the current allison and buy another for just a little money to boot?



Only mounts are on back of bell housing right?

 

[cjohnson1]

Only problem is there aren't many World transmissions out there laying loose and those that are are at a premium price. I've spent all weekend searching for a 1000, 2000,2400, or even a 3000.

All require a core charge and are going for almost as much as I have in the entire project so far. If I could find a burnt up or a roll over motorhome somewhere ther might be a chance. But $5,000 is way over my budget. The money tree won't bloom again for some time.

Still looking.



Brayden, Does all the pusher trannys rotate the same as the front engine trannys? The rear ends on a pushers are reverse rotation right? Seems logical! My AT 542 came out of a pusher. And it works correctly.



Robert, Tried to call you Saturday.



CJ

 

[Brayden]

As far as I know, yes you are correct.



I'm gonna give you a call tonight. .

 

[cjohnson1]

Great, I'm here!



I may have a solution, but, am waiting to talk to you before I jump on it.



CJ

 

[Brayden]

PM me your number again. . I tried calling you and I guess I got the wrong number. .

 

[cjohnson1]

OK guys, here's what I've come up with to solve this problem.



First, I don't want to scrap my AT 542 transmission. Especially since it's in an working. Hooked up and everything. SO, I'm going to keep it.



The Dana 70 gets a new set of 3. 54 gears to get the final drive close. May even have enough money left over to add a true trac in there. (For those muddy roads and campgrounds. )



To make up the difference it'll be short, I'm going to install a brownie box over drive / under drive transmission. It'll be between the transmission and the rear end. The Spicer 5831 C is what I'm looking for. Actually I have one located just haven't ordered it. With a . 73 od, this will put me in the 1900 rpm/ 70 mph range. The under drive is 2:00 to 1, so I can pull any steep mountain road I run across. This Spicer box is a 36,000 lb GVRW transmission, so it'll never be overloaded.



This entire set up will still be less money than a rebuilt Allison 1000, 2000, 0r 2400. Not to mention the $2000 core charge.

And all pieces will be rebuilt or new.



This should yield the most versatile set up possible.



CJ

 

[Barry]

Somewhere in the cobb-webs of my mind, it seems that the or a "limited" motorhome of that vintage came from the factory with a Gear Vendors... ... ..... was it Fleetwood or Holiday Rambler..... Just called my guru who was a Fleetwood Limited dealer at that time. He said the ones that did'nt come with the OD, they put it on so the customer could could down the road and still hear himself think... ... ... .....

 

[cjohnson1]

Originally posted by Barry

Somewhere in the cobb-webs of my mind, it seems that the or a "limited" motorhome of that vintage came from the factory with a Gear Vendors... ... ..... was it Fleetwood or Holiday Rambler..... Just called my guru who was a Fleetwood Limited dealer at that time. He said the ones that did'nt come with the OD, they put it on so the customer could could down the road and still hear himself think... ... ... .....

Your correct Barry, The gear vendor overdrive could be had for the C-6 transmission that used to be in the truck. But they have nothing for the Allison Truck transmission. I thought about going that route but it still wouldn't have given me the power I needed to climb mountains. That old 460 Ford motor would get down to 10 mph going up west out of Denver. Scary, very scary!!!!! And I went that route a lot. (Moab)



The Spicer Brownie box is less than half the cost of Gear Vendor anyway.





Funny fact, the original owner of my Limited used to live in Grandbury.

 

[Hutchew]

Just curious.....

How do you plan to shift the Brownie? Shift rods, cable or maybe solenoids?

The first truck I ever drove had two sticks, a 5 & 4. Made me learn real quick not to roundhouse the shifter on the brownie. Nothing more fun than trying to get the stupid thing out of two gears at the same time... ... ... .

 

[cjohnson1]

Re: Just curious.....

Originally posted by Hutchew

How do you plan to shift the Brownie? Shift rods, cable or maybe solenoids?

The first truck I ever drove had two sticks, a 5 & 4. Made me learn real quick not to roundhouse the shifter on the brownie. Nothing more fun than trying to get the stupid thing out of two gears at the same time... ... ... .

I'm thinking of using two boat shifter cables to connect the shifter up front and the brownie box mounted at the carrier bearing position. It will pretty much be a stick it in there and leave it. The main automatic transmission will do the shifting, the brownie box is for overdrive duties. The shifter is in case I have to climb out of a hole to get back to the road. Like the RV campground on the North side of Durango Colorado, or the boat ramp at the peninsula on the west side of Beaver Bend lake in Oklahoma. Ended up using my toad to push the MH up that one when the torque converter stalled. No room to get a running start. It will probably never see the under drive gear engaged but, wouldn't it be nice to know you could slip it into a tight spot without having to fan the brakes to death. A crawl ratio for the tight spots.

I don't think I could ever teach the wife how to split shifts!:--)

But the cool factor could be a blast.



CJohnson

 

[MPodawiltz]

Thumbs up on the brownie. I have played with the one sitting in my garage many times I dont think that boat cables would have a chance of shifting it. You are going to need something with levarage or some other kind of advantage (air, hydraulic, etc) . If I am wrong let me know because that solves a lot of my problems too.

 

[cjohnson1]

I have thought about an electric shift too! Finding a solenoid that would throw that far might be tricky. I know they exist because the Guys where I bought the Aux Box told me of one of their customers who rigged one up on his Pusher Coach to shift all three gears.

I would think an air shifter would be simpler. Those push pull air cylinders are used in a lot of applications.



Either of these would make for a much more professional install appearance. But, may be difficult to feel if the thing is shifting smoothly.



Actually either could be used. As for cables, I used a boat cable shifter many times in other applications with success. If you use a steering cables you can push/ pull with one cable. They will move a lot of weight. And, a bell crank can multiply a lot of effort and stroke. And I haven't made up my mind if I'll really will use the under drive part of this transmission. So, I may only need one shifter.



Here's a link to the info on the Spicer 5831 Aux-Box . I wrote the Author and asked him a few questions about my intended application. His info is why I am going ahead with the overdrive box.



I ordered a "C" model from Goody's yesterday. Should be here next week.



This project is taking longer than expected but I'm still under budget . It looks like it will be right on $ target with the rear end re-gear. If I go ahead with some some sort of limited slip or locker in the Dana then it will be slightly over budget. But, only by about $500 TO $600.



Next year the interior gets redone. Much much simpler physically. Only I think it will be the hardest ,cause the wife is going to want to help make the decisions. So far it's been, "you do what ever you think is right dear".

Anybody want a part in that phase??????



C Johnson