what is a dual transfer case?

[sixto]

I'm trying to make sense of this article - Dual Transfer Cases – Building the Crawl Box | Locktup 4x4 Tech Blog

It sounds like an overdrive unit between the transmission and transfer case. If so, why call it dual transfer case? Aren't transfer cases typically dual range (hi-lo) as is?

Sixto
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[SwampYankee]

Adding a second xfer case allows you to go HI-HI (first case in HI, second case in HI), HI-LO, LO-HI and LO-LO. Gives you more crawl options than just HI or LO depending upon terrain.

[BAVBMW]

Originally Posted by SwampYankee

Adding a second xfer case allows you to go HI-HI (first case in HI, second case in HI), HI-LO, LO-HI and LO-LO. Gives you more crawl options than just HI or LO depending upon terrain.

Yeah, but you forgot N-N, for when you really don't want to go anywhere!

MV

[P.C.]

Originally Posted by BAVBMW

Yeah, but you forgot N-N, for when you really don't want to go anywhere!

MV

I like the idea of having multiple reverse gear ratios!

[BAVBMW]

Originally Posted by P.C.

I like the idea of having multiple reverse gear ratios!

Newer Mercedes automatics do have more than one reverse ratio available, but transfer case(s) ratios will be the same forward and reverse. Just like a normal 4x4, you change every gear by the same factor. And being transfer cases, they're not really something you shift on the fly, you wouldn't go, R-Lo-Lo, R-Lo-Hi, to R-Hi-Hi as you gained speed while travelling backwards. You would pick the ratio best suited to your obstacle.

MV

[kerry]

Large bridge was installed over a 4 lane highway here. Built on rollers on one side of the highway and then a 'road' built across the highway. Outer end of the bridge was attached to the back of two trucks and they towed it across the highway. Those trucks had multiple transmissions back to back. Wide open throttle, turbos screaming, they may have been making 15ft per hour. Quite a sight to see. In fact, it took very close observation to figure out if they were moving at all. I can't remember if they were AWD or not. They did look like regular semi-tractors.

[panZZer]

they take the front section from a transfer case--that has the planetary gears, cuts that section of the case and fab a custom close off plate---with bolt holes to bolt up to another identical transfer case and sandwitch it imbetween the tranz tailhouse and the TC,
its a doubler.

[Fulcrum525]

Low Range/Crawler gears explained

http://www.4x4abc.com/4WD101/crawl.html

http://www.4x4abc.com/4WD101/lowcrawl.html

[SwampYankee]

Originally Posted by BAVBMW

Yeah, but you forgot N-N, for when you really don't want to go anywhere!

MV

That is true!

[Hatterasguy]

A lot of big trucks have them multiple options like that, they are good for PTO's as well.

Lo Lo on an old dump truck is usually like 2mph.

Modern trucks just do it with automatics and a lot of HP.

[Antony]

Not to get too off-topic, but all this low-low chatter reminded me of a friend of mine. He's got a 1992 Dodge with the Cummins diesel, 4x4, with the 5-speed manual transmission. He idles the truck, in 4 wheel drive low, 1st gear...and puts tire chains on while it creeps forward!!! I've seen him do it, funny to watch

[SwampYankee]

Originally Posted by Antony

Not to get too off-topic, but all this low-low chatter reminded me of a friend of mine. He's got a 1992 Dodge with the Cummins diesel, 4x4, with the 5-speed manual transmission. He idles the truck, in 4 wheel drive low, 1st gear...and puts tire chains on while it creeps forward!!! I've seen him do it, funny to watch

He is clearly not a safety geek.

I'd like to find one of those 1st gen Cummins (Reg cab, single wheel, 4x4) to convert into a personal workhorse with an aluminum flatbed dump and throw a 70's era nose on it. Hope they're not all completely oxidized by the time I get around to it.

[sixto]

Great discussion but the OC side of me still doesn't know what's dual about it.

Sixto
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[BAVBMW]

Originally Posted by sixto

Great discussion but the OC side of me still doesn't know what's dual about it.

Sixto
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Well, an ordinary 4x4 has one transfer case. For extreme conditions, some people modify the drivetrain by adding another transfer case, for a total of two transfer cases. Hence the "dual".

MV

[sixto]

My OC side isn't buying it. To me a transfer case splits the output. This device is a switchable over or underdrive at best that doesn't further split the output, but I'll shut up before the rock crawlers come to crawl over the rocks in my head

Sixto
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