Sprocket - thinking outside the box is cool. Like I said, you could do this if you could fabricate, or have fabricated, the adapters, mounts, intermediate shafts and so forth. but like I said soemthing like a Gear Venders over/underdrive probably would be less work to fit, and give you what it sounds like you want - very low granny, high enough OD for gas mileage on the highway.

Before I decided to build a 500cid twin-turbo stroker, I seriously considered using some "big truck" parts instead. I think it's the F500's and F700's that had a 429 with the "corporate" round bell housing, which is more or less a standard in the big truck industry. Rebuild something like that, then mate on a clark 7-sp, and you'd have tons of low gears and a final 1:1 ratio, to which you'd have to use lower rear axle gears to get any kind of mileage. THough a "big truck 429 and a 7-sp clark is about 1800lbs dry, so you've just added about 800-1000 lbs to the pickup.

What is cool is that the "big truck" 370/429 decks are similar enough to the 385 series engines that you can slap a pair of 460 EFI heads, and a 460 EFI intake, and apply fuel injection.

But, after spending countless hours researching, I opted to go with more "standard" stuff to make the machining easier. Just easier to find stroker kits and so forth.

Anyway, thinking out of the box is cool. Keep it up Sprocket.

 

Actually a NP435 is rated at around 435 ftlbs of input torque sustained (hence its name) With trannies compounded you could eisly exceed that capacity by 2 or 3 fold with a V8. Compounding NP 205 Tcases is a lot more doable because on a much higher input torque capacity.

 

i have been thinking along the same lines as already disscussed. i have a 1974 f250 with a divorced transfer case and have been wondering how to add gearing. i was also thinking along the lines of a second transfer case or a transmission. i was trying to keep the 4.10 gears because i have been told that the higher gears( 5.13) can strip the pinion gear as the higher the number the smaller the pinion gear becomes.

 

Just find the ZF tranny and the 1st gear(granny) is extremely strong for pulling through or something or someone. I have one and its a good one on my 88f150 300. The combination is strong not a speed demon, but that's not what I got the truck for either.

 

Old wive tail on stripping the teeth off usless you have a really light duty rear axle. They are no less strong on a 5.13 it is just that you can put more force on them by nature of the gear ratio. Something that I have seen happen more often is the drive shaft fails or you pop the head off of pinion with taller gear because higher drive shaft loads are needed and higher twisting loades ar placed on pinion with taller gear to get the same ground level torque. With a F250 if it has a D60 or so in rear and a D44 in front, you will not be tearing teeth off of gears, you will be breaking axles long before that happens.

 

4.56 gears have the fewest teeth on them, therefore they are thicker-marginally! like snoman said it isnt really a worry.. i've run big bogger tires with lots of power to them with a 4 speed and have never had the gears fail. i've broken spiders, axles, u joints, wadded up drivelines to no end, and snapped a pinion once being stupid, but never had the gears fail.. JMO

 

you'll either have more teeth taking up the load or larger teeth. As for torque on the tranny - considering the app, rock climbing, seems your not going to be pulling much weight at very low speed with little acceleration. If you try to use low/low to pull a boulder, or 4th/4th for speed I could see a problem.

Oh yeah, you'd be able to go 70mph in reverse!

Read a post a year or so ago on FTE a guy had done this very thing and it did work. Don't know if it lasted though.

 

Hey thanks, great to hear from someone who has actually worked with these.
So the Macks aren't the only trucks to use this setup? (something I heard)
Question: How do they get the extra ratios in the modern super tens?
is it a two speed rear like the smaller flatbeds, or built into the tranny?

 

My understanding is that most of the gears come from ranges/speeds within the transmission. For instance, a nine speed is 1(low creeper/granny), 2, 3, 4, 5, then a range shift with a switch similar to one used on a two-speed axle, and 2H=6, 3H=7, 4H=8 and 5H=9.

I didn't spend a lot of time on them but IIRC the old 13 speed Road Ranger, one of the earliest fully internal wide range transmissions, had, in addition to the main high/low like the nine speed, a splitter that added a high/low to the top four speeds. It would be shifted like the nine speed above except the high range would be 2H-=6, 2H+=7,3H-=8, 3H+=9,4H-=10, 4H+=11 and 5H-=12and 5H+=13. (or something like that)

I think safety had something to do with the demise of the duplex trannys since both transmissions were often shifted at the same time ... with the left arm hooked through the steering wheel.

 

The 13 speeds I dove long ago where 1st then 2nd L then M, then H and then on to 3rd L then M and so on. First was not compounded so you had a 5 speed with the top 4 gears compounded to give you 4 x 3 +1 equals 13 speeds.

 

You had me thinkin' I was losing it ... but here's a quote from another thread on multi-speed truck/bus transmissions:

http://www.geocities.com/gilligcoaches/Trivia2.html

"A 13 speed is a 9 speed with an over / direct splitter on the back. In both, first is a Low that is not repeated. You split only the top four gears in the 13 speed. This makes them 200 to 300 rpm gears and helps keep the engine speed near max torque."

 

Lets see when I was driving truck last year we had lo, double low, 1,2,3,4 switch to hi range 1=5,2=6,3=7,4=8 and you could split each gear with a splitter, 1,1.5,2,2.5,3,3.5,4,4.5 ect. Total of 18 gears. with a 400 big cam CAT pumped to 500hp all computer efi, even an electronic fuel pedal. Was a mid change thing. New electronics on the engine old style trannies. Shifting half gears realy helps getting to the top of the passes alot easier. Now most are super tens or auto's. Something to due with having wider power bands and shifting each gear at a slightly higher rpm. smog bull realy messed with the fuel mileage though on the newer stuff, anyway just rambling.
P.S I guese if I read the date on this post I wouldn't have said a thing, but I have it all typed out now, so here it is.