M211 Transfercase Swap

[Foreverunstopable]

Hey, just curious is there any transfer case that will swap into an existing M211 transfer cases place that would be 1:1 and have a low? I've seen http://www.cckw.org/speed.htm and was curious if anything would work with the same mount and drive flange.

 

[rosco]

Yes - (don't know the Military designation), but its the T-case of the GM vehicle, prior to the M211. It had a 2 speed T-case, however, its somewhat lighter, coming from a lighter truck. It will virtually bolt up. I don't remember exactly all the details - it was around the early 70's that I did it.

That said, the question begs: What are you going to do with the M211's auto tranny/T-case? In fact, you can go into the M211's T-case, take the bearing out of the center of the large gear in there (that otherwise makes it an idler), and you will have a two speed transfer case. It has the sprague drive front axle that is controlled with the 211's gear shift linkage. And while that is not too consuming, you can replace the 4 speed auto, with the 5 speed OD, if you change out the bell housing, add rear engine mounts, and hang a clutch pedal. There are probably a few details that I have forgotten, but those are some of the big things. I know about the stock T-case, because I blew up, the lighter version I mentioned, when I was trying to pull out a bogged, loaded, M211, using both the winch & gear box in low range.

Was the change worth it? Not sure - just thought that I didn't like auto trannys at the time. I have driven both the stock M211 & the modified one with the 5 speed, from Prudhoe Bay to southern Alberta, several times. They were both good - still have them - parked.

Lee in Alaska

 

[Foreverunstopable]

The truck never had the 211 engine or transmission, just the case, axles. Can you please provide a picture of what your talking about in reference to the T-case two speed conversion? Preferably with more detailed instructions? I have the manuals but am still learning about mechanics, I need it Barney style. Thanks!

 

[Elwenil]

Doesn't the M211 transfer case rotate the front driveshaft backwards? Does the previous vehicle also have that odd feature?

 

[Foreverunstopable]

The M211 has the reverse rotation axles and case. The C-6500 has the M211 axles as well.

 

[rosco]

I did that conversion, many years ago. I have no T-case out or open. Just take the one you have apart - trace the power through it. You'll see the gear. Its in the center on a splined shaft. Its center hub has a large bearing between it and the outer gear ring. Shrink fit a piece in place of the bearing - then you'll have two speeds. You need considerable shift linkage to control the front axle sprags.

It will be a good place to learn mechanics. Take the lid off, clean it out nice, rotate that input & see what moves & where. Figure out how it works. Keep in mind, that you are doing the easy part. The hard part was inventing the whole T-case & getting it right.

Lee in Alaska

 

[Foreverunstopable]

Lee, any idea of the ratios after this? Also what does shrink fit a piece in its place mean? How much is "considerable" shift linkage? Does this allow the case to disengage the front axle completely rather than AWD? Sorry I always have plenty of questions.

 

[rosco]

"It will be a good place to learn mechanics. Take the lid off, clean it out nice, rotate that input & see what moves & where. Figure out how it works. Keep in mind, that you are doing the easy part. The hard part was inventing the whole T-case & getting it right. " .......... You need to do some of this, as I mentioned! Then, you will understand some of the fundamentals, like replacing that bearing. It will take advanced machine work. The gearing will be what-ever, I think the standard. Low range will be about half of high range. The front axle, is full time - linkage needs to be made, to control the spragues, each time there is a shift from forward to reverse.

Lee in Alaska

 

[Foreverunstopable]

When I called Tulsa some months ago I found an employee who remembered building this truck. He said the case normally needed to actuate that sprag for reverse but that there was a modification done. Apparently they knew of a mod you could do that worked around the need for actuating that in side the case, you could drive forwards and reverse with no issue. Doe this sound correct? I know with the drive shafts out the transfercase will rotate forwards and reverse without moving the sprag.