Install a transfer case backwards?

[Shaneajanderson]

Here I come with another dumb idea.

I just got done reading about the guy who ecomodded the Austin-Healey way back in the day with a second transmission hooked up backwards, and it got me thinking: Could I put a transfer case on a 4wd pickup backwards and get a massive overdrive? The 4-Low is something like 4 or 5:1 as just a wild guess, which backwards could give somewhere in the realm of .20:1 to the rear differential. This would allow a really low rear gear set to be used in this configuration for cruising, but throw it into normal mode for really good pulling.

The only thing I doubt is if the transfer case itself could handle the high internal RPMs.

[oil pan 4]

You don't want a 0.2:1 over drive.
Unless you are running a really weird tire size and rear diff ratio that doesn't make any sense.
Really the most over drive you will find useful would be some where around .4 or .5 to 1 with normal diff gears and tire size.
If the engine runs too slowly it bogs down, doesn't make enough power, the internal vibrations hammer away at the connecting rod bearings until the engine fails.

[rmay635703]

Many old 2wd t-cases were 2:1 reduction

Run in reverse would be very noisy

Better to run them as designed in front of a very high rearend ratio like 2.8 or even 2.5

Then you will gain 5 useable gears, just make sure the t-case is the type you can upshift while rolling

[Shaneajanderson]

Originally Posted by rmay635703

Many old 2wd t-cases were 2:1 reduction

Run in reverse would be very noisy

Better to run them as designed in front of a very high rearend ratio like 2.8 or even 2.5

Then you will gain 5 useable gears, just make sure the t-case is the type you can upshift while rolling

Thanks, this makes much more sense actually. My thought was to switch to like something like a 5.11 rear end for my heavy towing, and use the t case to basically get me close to normal/current 3.55

[19bonestock88]

Most low ranges aren’t 4:1 or 5:1 anyway, it’s far more common to find something like 2.75 or 3:1 which still would provide an absurd overdrive... maybe if you used something like a Rockwell axle with its 6.72 ratio?

[Shaneajanderson]

Originally Posted by 19bonestock88

Most low ranges aren’t 4:1 or 5:1 anyway, it’s far more common to find something like 2.75 or 3:1 which still would provide an absurd overdrive... maybe if you used something like a Rockwell axle with its 6.72 ratio?

Yes after more reading on transfer cases I find that they are typical between 2:1 and 3:1. The numbers I gave were my guess of how much higher my RPMs are at a given speed in my pickup when in low, but I have no tach so it was pretty much just a guess.

I've never really had much use for 4-low in reality, but if you leave the front hubs unlocked and lock it into low it makes backing a trailer with a manual trans much much easier, especially if you're backing into a tight spot.

I'm going to do some research on adding a second transmission, most likely backwards. If I could find a 3 speed that had 1.25, 1, and 0.75:1 ratios and hook up straight that would be great, but I doubt such a thing exists.

[19bonestock88]

A company called Atlas makes nice transfer cases with really low low ranges (for rock crawling), and I may have heard of a three speed transfer case that has an intermediate low and a “super low”

[oil pan 4]

To get something for numerically lower than about a 3.32, 3.325, 3.21 to 1 ring and pinion is going to be just about impossible to find.
The lowest I have ever seen with my own eyes was the 2.5x to 1 set on a GM 8.5 inch 10 bolt made in the 1970s.
But those 2.5 sets went the way of the 2 speed automatic and 3 speed manual transmissions.
Actually I still know where the only one I ever saw is, it's still in use, kind of.

[rmay635703]

Originally Posted by 19bonestock88

Most low ranges aren’t 4:1 or 5:1 anyway, it’s far more common to find something like 2.75 or 3:1 which still would provide an absurd overdrive... maybe if you used something like a Rockwell axle with its 6.72 ratio?

http://www.nmc-wollard.com/uploads/c...l-7-12-Sml.pdf

The older version of the thing above sold as a Dodge flightsomethingandanother on govliquidation had an 8:1 rear gear ratio and sold for $500-$2000 a pop,

I would estimate the place above could source and sell you a Dodge 8:1 rear diff as spare parts

[19bonestock88]

It still begs the question, why install a ridiculously low final drive and have a backwards transfer case to allow freeway use when you could have normal gears and the transfer case mounted correctly and have the towing when it was needed?