Thoughts on overdrive.... has the tcase been looked at?

[Trango]

So I'm sitting here, watching the BoSox get closer to sweeping the Rocks, and I'm searching on tcases because it's been too long since I've been in the garage.

Check out the specs on the 1702 tcase by fabco:

http://fabcoautomotive.com/products/fs_twospeed.htm

http://fabcoautomotive.com/products/body_tc1702.htm

The thing has a .85:1 high range.

I realize that Tom has done a fantastic job in designing or finding different gears for the 3053A... and that's great.

Have there been any thoughts on putting a different high range gearset into the tcase? Even if you were using the tcase to split shifts (which I'm currently doing when I drive this thing in traffic), you'd still be able to shift from low-5th into high-3rd, or maybe even high-4th.

Just saying. I'm so far behind in what I had hoped to accomplish with my vehicles this year that I can't hardly afford to even spend my attention on this stuff... but this is just an idea for you guys looking for a solution within the confines of the stock driveline.

 

[gringeltaube]

.............
Have there been any thoughts on putting a different high range gearset into the tcase? .........

Yes, a lot....! Our T-cases are a perfect example of compactness and simplicity!
I'm still trying to figure out how to avoid extensive (expensive!) mods.
Not so easy to KISS... (Keep It Stupid Simple)
G.

 

[Trango]

RE: Re: Thoughts on overdrive.... has the tcase been looked

My thoughts exactly. I like these cases - they're syncro'd, easy to shift, and work great even on pavement at speed.

If someone had the gumption to put together a .80 high-range or something, even with my extensive mods, I'd still probably be interested.

It would be the antidote to 6.72, across the entire tranny range.

 

[m-35tom]

RE: Re: Thoughts on overdrive.... has the tcase been looked

ok, what is the cost in $$$

 

[Trango]

RE: Re: Thoughts on overdrive.... has the tcase been looked

Well, this is just a brainstorm and an open question, so I wouldn't have the foggiest about cost to put gears together.. if they are just gears woodruff'ed onto a shaft, it wouldn't be bad, but an entire new input or output gear/shaft combo, well, I'm sure you're familiar with those costs.

The thing is that I'm honestly not sure if the 1:1 high range is even gear driven (or if it's just a slider engaging the shaft for true direct drive), anyway.... that would dictate the feasibility of this mod. I was hoping to see if anyone's looked into this before I dig into one of these cases.

Best,
Bob

 

[m-35tom]

RE: Re: Thoughts on overdrive.... has the tcase been looked

well it sounds like the tc-1702 has only 2 shafts so rotation would be backwards to start with. low is much lower and that might not be a problem, but rules out split shifting. also it puts all gears at a higher ratio, not just 5th. i am sure you will find cost is very high.............. just my .02¢
tom

 

[Trango]

My apologies for being unclear. I am wondering if anyone has put thought into creating another gearset for the stock M35 transfer case, to raise the gear ratio (numerically lower the ratio) for high gear. I bring up the fabco case only for reference.

Best,
Bob

 

[gringeltaube]

Bob, if you take a look inside that case you will understand why it's not just changing a pair of gears...
Unlike other T-Cases (e.g. Ural) ours have three equidistant shafts and the only 3 gears involved in high range are 33/22/33 teeth on input, counter- and (F/R) output shaft, respectively. That makes the 1:1 high ratio. If we tried to change any of those gears it would affect the other two. So, the only other way left is to add a pair of gears somewhere between counter and output shaft. In e.g. to achieve a .84 od ratio, that set would be a 31/26T combo. Without bigger mods those gears could be placed in the middle of the case between high and low gears, mounted centered on each shaft, but... there we have the large synchro unit on the input shaft, responsible for easy up and down shifting, a feature we sure dont want to miss...!

Like I said before, not so easy...!

 

[Trango]

Muy barbaro, amigo! I really appreciate the detail and description.

If nothing else, I am happy to cross this off the list of potential projects.

 

[SasquatchSanta]

To make my Deuce run faster I'm gong to so something I saw on the Rocky and Bullwinkle show.

It's really simple. All you have to do is remove the glass lense from the speedometer. With the lense removed I can reach over and twist the speedometer needle to whatever speed I want to run.

Hummm .... I wonder if it would also work in the opposite --- like of you had to stop real fast ... you could reach over and twist the needle to zero ... Hummm

It's going to be a long winter.

 

[Blood_of_Tyrants]

To make my Deuce run faster I'm gong to so something I saw on the Rocky and Bullwinkle show.

It's really simple. All you have to do is remove the glass lense from the speedometer. With the lense removed I can reach over and twist the speedometer needle to whatever speed I want to run.

Hummm .... I wonder if it would also work in the opposite --- like of you had to stop real fast ... you could reach over and twist the needle to zero ... Hummm

It's going to be a long winter.

You could also drive it off a cliff. No problem because you have AIR BRAKES, right?

 

[Blood_of_Tyrants]

But seriously, what if all three gears, the 33-22-33 combo, were changed out to be something more like a 31-28-26....

 

[Polverone]

... Hummm It's going to be a long winter.

So is there a small 2 speed gear box that could go between the Trans and Transfer case?
Make brackets to install the new gearbox
Move the transfer case back
Relocate the 2 cross members around the T-case
Reposition the spare tire to accommodate the new placement of the parking brake
Fabricate 2 new input/output drive lines to the 2 speed housing
Shorten the rear drive axle
Lengthen the front drive axle
New longer speedometer cable and gearing...

Good thing winter is just starting! Of course, I jest here.

When I can afford 10 new 11/20's I'll be "cavorting" in tall cotton with a little more top end.

 

[Blood_of_Tyrants]

It would be easier to have someone fabricate new gears for the transfer case.

 

[gringeltaube]

But seriously, what if all three gears, the 33-22-33 combo, were changed out to be something more like a 31-28-26....

Very seriously: The distance between input- and counter shaft is 5.5", same for counter shaft to output shaft. All three gears are in constant mesh and obviously have to have the same diametral pitch ( number of teeth per inch of the pitch circle diameter). So theoretically you can run almost any combo as long as first and last gears are the same size and tooth number but you can't just decrease the number of teeth of one (the output) gear without also reducing it's diameter and accordingly the distance between centers of counter shaft and output shaft.
The only way to achieve any overdrive high ratio would be somehow shortening the case or better building an entire new one!
Better than thousand words, some illustrations of (theoretical) mods and resulting od ratio.

G.

 

[Blood_of_Tyrants]

Yes, I see the error in my logic, now. Basically, you need a new case as well as new gears.

 

[m-35tom]

it's just money..............

 

[El_Guapo]

It would appear that if you were willing to loose low range it could be converted to 'overdrive range.' I would think that the loss out weighs the gain, however.

 

[OPCOM]

Wouldn't want to lose low range.. good for pulling houses down and such. Been looking for a case that could be put behind the transfer, the idea being that you don't need 6x6 on the highway at 55MPH or better. All the ones I see so far are designed to bolt to an existing transmission, rather than the 'old style' separate ones.

There is a post here up front about the Fabco that shows a separate case presumably to replace the original, but not sure how to make sense of the specs except that it seems to be for replacing the original.

Rather have just a simple rears-only case, just for using on the highway for 5th OD (and maybe in the 3-4 shift). Woe be to him that engages such a thing when in 6x6 mode! some kind of pneumatic/electric lockout could be made up easily.

 

[Recovry4x4]

Perhaps a planetary bolted to the rear output of the transfer case Patrick. You would lose your parking brake.