Use a Transfer Case an an OD Unit!?

I saw the below post (quoted) in this thread:
http://www.jalopyjournal.com/forum/showthread.php?t=284946

Has anybody on here actually done this? It sounds intriguing...

~Jason

 

one problem i see would be shifting it at speed old transfer casees aren't the easiest to shift you could just leave it in high but why not just put taller gears in your axle

 

I was exploring ways to retain an 8-lug F2 rear end, albeit with higher gears.

The general consensus is in the link above. But I ran across this idea, and thought I'd post it, as it seemed to merit it's own thread.

~Jason

 

With alot of the old transfer cases, you needed to be in nuetral or at least stopped to shift them from high to low. Lets just say, the ones that I drove that were made before 1988 anyway.


Larry

 

I saw a 69 C-10 chevy with a 455 Olds/TH400 running a Ford 3-speed mounted backwards behind the automatic for Overdrive.

 

The gear splits in transfer cases are unreal and would likely result in one range being useless. I'd either go with a rearend swap or adapt a late model truck 5 speed with overdrive. good luck

 

Man, even with a 5-speed OD, I'd STILL have a 55MPH top speed.

~Jason

 

Thats the problem with such a low geared rear, as I said the OD trans alone likely will not cut it, but maybe you can put a gear vendors OD behind the 5-speed (I know you said you didn't want to be in the gear vendors price range). I like the idea of putting a 3spd backwards behind the trans, 2 shifters

Just to have the bragging rights that you got something like that to work would be worth the effort. I might need to get myself a big truck just to do that.

 

You can't change range on the fly in any transfer case that I've ever seen.

The Dana 20 in my truck can be shifted from 2wd to 4wd while rolling but only if the whole drivetrain is turning (front hubs locked) you can't shift from low to high without coming to a complete stop and putting the transmission in neutral.

The gears are straight cut and there are no synchronisers, it's not really built like a transmission, more like the gearbox on a lathe.

You could use a divorced case like a NP205 or a Rockwell as a 2-speed unit but you would have to pick low or high before you got rolling. Mount the T-case backwards and you're good to go.

Most transfer case ratios are 2:1 or lower. In fact 2:1 is considered a pretty poor reduction ratio in the 4x4 world. Most aftermarket cases are in the 3:1 or 4:1 range now.

Shawn

 

Not to argue, but I had a NP205 in a '82 Chevy 3/4 ton when I was a teenager. All I had to do was drop the trans into neutral and move the selector in the Tcase. This did work weather the hubs were locked (had manual hubs) or not.

Would you still have to do this if you do the method you and I pretty much both described above? Take off in the low range for running around town or what have you, then drop it into neutral to shift the Tcase, and then resume operation? I do know there was the occasional grinding as the gears were switched in the trans case, but the gear-to-gear 205 was a solid sumbitch. I know it is possible to grenade them, but I'm sure it would take a ton!

This could be even better for the reduction properties. If it ran at 3000rpm to hold 50mph before, with 2:1 reduction it theoretically would run the same speed at 1500rpm? And with the 3:1 reduction, it would do the same speed at just off of idle?!?!? Therefore, it should be able to handle 70mph at... damnit, let me get my pencil and paper out.... between 1400 and 1500 rpm?

Depending on the powerband of the motor in the truck, that could be almost perfect. The only other question I would have is - Would the rear end and gearing be able to withstand those speeds?

 

Likely, as the thread linked in the first post of this thread suggests, I'll end up with a 8-lug 9" rear from a '68 - '72 F250/F350. I'd only recently heard of using a transfer case in this way, and thought it was interesting, and might be better explored in it's own thread.

~Jason

 

So you could change from low to high range on the fly? Are you sure it wasn't a NP203 chain driven case? The 205 is all gear driven (Or my memory is bad). Chain cases usually use a planetary reduction box. Gear cases use spur gears for reduction.

I can go from 2wd to 4wd no problem but not from low to high.

Maybe the 205 is different, if it is that would be perfect for a cheap O/D box.

I wonder if you would have to add an oil pump and cooler to keep it from eating itself over time. After all, you're going to be feeding it backwards and probably running it that way for much longer periods than it was designed for.

Shawn

-edit-

What about using just the planetary range box from a NP203 for an O.D.? The Jeep guys double up the range boxes to get extra reduction, couldn't you just run one backwards?

 

If you're gonna use a 9", just pick the right rearend gear ratio, there are a whole bunch available. If you need a steeper gear for low speed use, put the transfer case in it in the normal configuration, and it will give you the same low speed crawling ability as any other 4x4.

 

umm he may have been able to shift it from high to low but it would have been VERY tricky and made some awful noise. even double clucthing it was on the hard side of difficult and took more time than just stopping to do it.


I like the idea of the backwards three speed...would it last??

 

With the reversed transmittions like putting a three speed backwards behind another 3 speed to make an overdrive how do you hook the driveshaft up?

 

With experience on semi transmissions, I don't think using a transfer case like that will work very well. The transfer case low range should be around 2.50 or 2.60 reduction ratio. I think that trying to use that as an overdrive will cause the gears to overheat, and not enough oil capacity to attempt to cool them. I know big truck overdrive trannies are an extreme for a comparison, but I see .74 ratio overdrive gears burnt up on a regular basis.
I've been dreaming of making an overdrive box for my 65 Chevy P/U using gears from a Fuller big truck tranny, but making the case accurately and strong is one step, input shaft and custom main shaft the next step.
I can't think of any auxillary overdrive unit that has a gear ratio much taller than .80, unless you took an old Brown-Lite (unsure of spelling) and ran it backwards. The gear reduction would make for a less drastic overdrive. These gearboxes would be mounted to the frame between the tranny and rearend, requiring driveshaft work.

 

years ago a friend put a brownie box backwards in his 61 C40 truck. Probably not the most efficient way to go, but it worked.

 

If your 8 lug F2 has the old standard 8 on 6 1/2" bolt pattern, a rearend swap to consider could be from a mid '80's 3/4 ton Chevy. Some of them came out with a 3.42 ratio 10.5" ring gear 14 bolt cover rearend. One quick identifier for this rearend is the 14 bolt cover on the rear, and a 6 bolt retainer at the pinion yoke. A lot of these rearends came with 3.73 and 4.10 gears. There were even some 9.5" RG rears that had the 3.42 ratio. These axles are a c-clip type axle like a half ton, instead of the full floating type axle like the the old F2, the 10.5 Chevy, or big trucks.
This leads to the next question. Can the driveshaft be modified to accept a 1350 series weld yoke to match the pinion yoke on the 14 bolt rear?

 

Actually, the '68 - '72 (I believe) 9" rears are a bolt-in! Believe it or not!

~Jason

 

Abomination, are you wanting to stay with 8 lug wheels? 9" Ford pickup rearends were always on Ford 5 on 5 1/2" bolt pattern from '57 to the end around '86 or so.
The Dana 60 3/4 ton rearends had 8 lug wheels, but most had low gears. Back then, if a 3/4 ton truck was bought, it was needed as a work truck. The tallest factory gear ratio was 3.55 and few fell out of the Ford box with that ratio. Most were 3.73 and 4.10 if not lower. The 3/4 ton rearends were close to the same width as the 1/2 tons because the shared beds and some front end parts on the heavier frame.
The only thing holding a guy back on putting a later rearend in would be---width, adjusting axle seat positioning, custom u-bolts (PM here), u-bolt plates, brake line plumbing, and driveshaft work. Wait, one more thing, money.

 

I think Abomination was just a little confused about the type he was looking for. He has seen a lot of talk about the 9" as well as the Dana 60, so he just confused them here (but it is good to remind him)

So what you are saying is that the '68-'72 Ford Dana 60 is a different width than the F2/F3? Do you know what the measure between the wheel mounting surfaces is for the '72? I have read that the width, and the spring location is the same as the older F2/F3.

 

And your driveshaft better be PERFECTLY balanced

 

An alternative would be the Planetary gear OD used in Mid 70's to late 80's Volvos. These are a small unitmade by Laycock, patterned on a Borg Warner design. In the volvo they mounted to the back of the regulr 4 speed trans, and were electrically operated with a push button on the shift lever (momentary switch push on push off) also had a 4th gear only deal so down shifting disegaged it. Should be plentiful and cheap unless the crushers have gotten them all lately. look for 740 and 740 also 240 and 260's. Can also be found in jaguars, rovers, triumphs. Basically bullet proof, had one in a volvo 940 wagon. Stock engine was 170 HP, It had been breathed on a bit and put out over 200, and the OD was more that up to the abuse I put it through. I believe the model number is M46. They are popular with the Model A touring group as they are easy to install. I believe the OD is .73.

 

Here is a pic of one mounted in a modle A torque tube.
http://www.thelmasgarage.com/volvo.htm

 

The '70's Jeep Quadratrac tranfer cases can be shifted with the tranny in neutral, up to about 10mph. You can get part-time kits, to lose the limited slip problems. It's a stout unit, some folks used them for desert racing.

 

Is this kind of like the Gear Vendors unit?


~Jason

 

I'd say similar, with the difference being upgrading of parts to withstand more torque in the Gear Vendors unit, plus a hell of a lot of effort in the area of development, testing, creating adaptors and kits...

 

if your looking for a higher gear 8 lug find a dana61 looks just like the dana 60.they came in early 80s ford&dodge 3/4vans and some pickups.,3:00 and 3:50 ratios. mounting the t-case backwards wont change the final ratio.in 2 wheel drive the ratio doesnt change .if you need dana 61 b.o.m #s i have them...

 

You guys were right - I had the 9" and the Dana confused.

If I fine a DANA from a '68 - '72 F250 or F350 THAT'S the ones with the spring perches, etc right in the same spot as my '50.

I do have the wider rear fenders, and thusly, may be able to accommodate the 3"/side wider rears though...

~Jason

 

A transfer case isn't really designed to be run in low range at high speed. The oiling for low range is good enough for short low speed bursts, but the high range gets the lions share of the cooling resources. I would look at something else.

There are the Doug Nash overdrives, I think US Gear makes them, and then Gear Vendors. Neither will be cheap though. Clark made a 5-speed OD but I can't remember exactly the model. They came IHC's alot, Fords had them too, but most of them were 1:1 high.