alright, i like this idea because it would save me the cash outlay for ring and pinions, plus provide me with a neat overdrive system.

run an auto to a doubler type of setup, with one of the cases in low all the time.

then, run 4.10s in the diffs with my 42s.

effectively making the ring and pinion ratio 8:1 (1.96 NP205 low). once i got up to about 45mph, i could shift the one case back into high range, giving me a 4.10:1 diff again.

at 3250rpm in top gear with the cases both in high range, i would be doing 99mph. i think that this owuld be a great ratio for highway cruising, but at the same time i think that it is a bit of a wide range between the two.

so i guess my question is, would this work alright? would shifter a tcase into high from low work at 45-50mph?

the more i think about it the more i think it would be a PITA, but it would be nice to have the ability to cruise. im thinking a manual valvebody would help on the auto.

comments? and no i have not been drinking tonight :D

many advantages to that idea.
slow driveshaft speeds = less vibration whipping
double trannies and 3.54 gears is where i am heading

Originally posted by 9-Volt


at 3250rpm in top gear with the cases both in high range, i would be doing 99mph. i think that this owuld be a great ratio for highway cruising,

id like to see you hold that speed on a 8* grade, but maybe where you live there are no hills like hear in BC

i already thought of doing this with a brouny box or a 3 spped trany I got out of a IH truck

Originally posted by 9-Volt
once i got up to about 45mph, i could shift the one case back into high range, giving me a 4.10:1 diff again.


Ummm what t-case would you be using? I can't really think of one that can be shifted on the fly from low to high like that, especially at 45mph. You'd need some sort of syncroed case or something. The 42s are going to provide a ton of overdrive effect anyways. 4.10s and 42s seems like a bit much OD to me, especially for a 4-popper, which you have right?

I think what your describing is a underdrive system :rolleyes: :rolleyes:

Not overdrive! :flipoff2:

four popper no more, i realized that i should do it once, and do it right. big block ford is what i have decided on. why ford? well because i could stroke it to

806 CUBIC INCHES

if i wanted to :eek:

My old K30 had 42's with 4.10's and a TH400 / 205 Tcase. The auto helped a ton on getting the rig moving from a stop and the 4.10's were great for cruising down the road. Off road, the 1.96:1 SUCKED. I needed LOTS more gearing to move that truck. I always did pretty good but really needed some more gears. I now have a TH400 / 203/205 setup with 4.88's and 44's. This works really nice for driving and the cruising RPM are not that bad. The extra 2:1 in the 203 is :smokin: NOW, as for shifting the 203 while moving, it's not real easy. Just make sure that you shift the tranny into neutral when you are going to your "high" range to help reduce the gear bashing.

you can shift almost every gear drive TC from low to high at any speed.
it is just a 2 speed tranny.

mnstr,
if you shift the tranny into N how the fawk do you match the engine rpms to shift the range box?
do you just pull til the grinding stops?

downshifting
if you leave the tranny in gear and shift range box into N, then double engine rpm (2:1) the gear speeds should just about match and it will go into L on the range box.

upshifting you obviously drop the rpm in half then shift it in.

Originally posted by mj
you can shift almost every gear drive TC from low to high at any speed.
it is just a 2 speed tranny.

Yeah, but it's not synchroed and for some reason they don't ever seem very willing to be shifted on the fly, even with double clutching and RPM matching.

I dont have any trouble,
I dont use the clutch
but I am a truck driver and shift nonsyncro tranny all day for a living
I hate syncro/blocker ring trannies

My old truck had a 205 and my new truck has a 203 / 205 in it. Shifting the 205 through neutral is a PAIN. Shifting the 203 is usually not too bad while rolling fairly slowly.

Trying to shift from low to high while cruising down the road at what ever speed , (example 40 MPH), would be a totally different subject. Shifting your big rig tranny is probably much easier than shifting the 203 will be. The big rig has a much closer gear split, (not 2:1), and more inertia to the rotating system. Trying to match a 2:1 engine speed split would be hard, but by sliding the tranny into neutral and letting the shaft coast down, you might get it to "drop" in. It was just a thought, I have never tried this on my rig at highway speeds. Slower speeds it seems to help.

Originally posted by mj
you can shift almost every gear drive TC from low to high at any speed.
it is just a 2 speed tranny.

Correct me if I'm wrong, but it is essentially a 2 speed tranny with NO CLUTCH (or torque convertor). Seems to me that would add up to some serious gear mashing.

so you are unable to shift without using the clutch?
are you old enough to drive yet son? :flipoff2:

why bother putting one in low and THEN shifting for high.....just to cruise!!

GAY

with 800 cubes, i dont think it will be a bad problem to just drive it

(that guy a couple posts back did it with 44s)

just DO IT,

I run a Toy four popper, Toy five speed, 2.28 box into a 4.7 box, 4.10's and 44's. I leave the 2.28 box in low range all the time. If I upshift the 2.28 box, I can't get it to move off the line without slipping the clutch for what seems like hours.

I can upshift the 2.28 box on the fly if I have to, but it doesn't like it--MJ, you're a better man than I if you can do that on a regular basis without grinding up couplers.

Even if I do upshift the 2.28 on the fly, the truck runs out of power in the middle of Third--with the 2.28 in low, I can run till I run out of power in Fifth (in low) at around 60mph.

I really only upshift the 2.28 when the 4.7 is in low, on milder trails and in between obstacles.

real easy with the 205s 1.96 gearing