Need opinions on axle gearing

[Cirbo]

Ok... I've got a concept truck in my head that I'm trying to put down on paper. I'm accumulating parts now for the build.

'67 FJ45 long wheel base
33 or 35 inch tires (would like to use 35's)
'78 vintage front and rear FJ40 axles
Turnkey Engines Vortec 5.3 aluminum motor 350hp/350lbft
Advance Adapters Ranger Torque Splitter (27% overdrive)
'78 vintage H42 and matched transfer case from an FJ40
ARB's installed front and rear

So the question is this:

With the 33's or 35's and the Ranger OD, what choice should I make for gearing?

4.11?
4.56?
4.88?

The plan for the truck would be to use it as a daily driver, mild wheeler, hauler. (I say mild wheeler with that kind of body length)

Thoughts and ideas?

TIA,

jC

 

[Cirbo]

Another fly in the ointment.... I was playing with gear ratio calculators.

With the 4.88's, I get a final drive ration of 34:1.

4.56 gives me 32:1.

4.11 gives me 28.5:1.

I can get slightly better than 40:1 if I manage to install 2.31 gears from an older transfer case.

What is the net result of riding around with the overdrive engaged on the street?

 

[kcustom73]

I went thru some of these calculation a while back and decide the best combo for me was to swap to a gm 700r4 auto with marlin crawler toybox, stock t-case, 3.70 gearing and 33" tires. For me this is going to be a DD that I travel long distance to go wheeling and camping with the family so I wanted really good highway gears but still have some good off-roading. With this combo, I'll be cruising at 1800rpm on the highway at 68mph (this is a good rpm for fuel mileage with the diesel engine I'll be running) and still have about a 50:1 crawl ratio.

With a long wheel base you might want to consider some of these non-toyota options. Hope this helps

 

[PPFJ60]

Since you say you will use it as a DD and only mild wheeling you shouldn't be as concerned with the crawl ration as much as you should be looking at what RPM's you will be running at specified speeds.

Bigger tires cost more so if you plan on spending most of the time on the streets stay with the 33's and 4.11.

More fun off road would be 35's and 4.88.

I vote for more fun and then even more fun which means bigger and bigger tires.

 

[Tapage]

with that powa .. I would keep around 4.56 if you are not going up on tires and if you are going to keep in the light off road side .. if you know yourself and will jump on 37" next year ( or less ) and gonna push on more off road ... 4.88

 

[CruisinFJ60]

35" tires and 4.56 gears will net you a stock gearing ratio through all gears. and would be a good all around vehicle since it would be under or over geared in the city or on the highway. You could do 4.11 as well if you wanted but your spedo would read slower than you were actually moving and the engine will have enough power to move the truck pretty well. but since you are gonna have the overdrive i would run the deeper gearing simply for the stock driving feel of things.

 

[Josie'sLandCruiser]

Hi All:

I have a buddy running the 5.3L GM V8 with a SM465 four speed and the classic "three-speed" t-case along with 4.11 diffs and 37 inch radial IROK tires.

This combo seems to work quite well for him!

Regards,

Alan

 

[Fast Eddy]

I have a buddy running the 5.3L GM V8 with a SM465 four speed and the classic "three-speed" t-case along with 4.11 diffs and 37 inch radial IROK tires.

That is the recipe for a cracked-in-half t-case.

 

[orangefj45]

you're over-thinking this build. run an h55f with the split case and you're styling. quiet, smooth shifting, extremely reliable, bolt-on, very useable gear-splits, good low range, no doubler needed,........

 

[Cirbo]

you're over-thinking this build. run an h55f with the split case and you're styling. quiet, smooth shifting, extremely reliable, bolt-on, very useable gear-splits, good low range, no doubler needed,........

Would love to do that, but I'm working with a limited budget. (ain't we all! )

Thanks to all for your input. Now matter how I do the calcuations, that 27% OD just mixes the thing up. It's a bigger jump than I'd like to see, but the price was right.

Georg,

I'll need to get you to send me some transfer case support as well.

jC

 

[orangefj45]

Ok... I've got a concept truck in my head that I'm trying to put down on paper. I'm accumulating parts now for the build.

Turnkey Engines Vortec 5.3 aluminum motor 350hp/350lbft

jC

run an h55f with the split case and you're styling.

Would love to do that, but I'm working with a limited budget. (ain't we all! )

huh? you're gonna spend thousands more than you need to by going with a turnkey engine but the $3k for an h55f/split case combo isn't in the budget?

i'd say go find yourself a low milage wrecking yard 5.3 for $700-1000 along with a howell harness and whatever else you need. you should be able to get all the parts for the vortec for $2k; engine, harness, computer and fuel system.
your first gear low range with the h55f and split case will be 48:1 with 411s in the diffs. that outta be enough for mild wheeling. if not, then go to 488s and you'll have 57:1

just thinking out loud........

georg @ valley hybrids

 

[orangefj45]

Georg,

I'll need to get you to send me some transfer case support as well.

jC

send me a pm and i'll make it happen!

georg