[Pedestrian]

I have a set of detroit locked 5.38 geared axles lying around that I was planning on using in an early Bronco cralwer project. I have come to the realization that that project will probably not be built in the forseeable future.
So I was thinking about putting them into my 79.
I'm only running 35-12.5x15s a mild 400, C6, and a doubler.
Am I just going to cause myself serious breakage issues??
Thoughts, recommendations???

 

[379sinvb]

Sounds like an awfully low gear for a "small" tire. What would be the purpose of the truck, what do you mainly do with the truck?

 

[79F150]

Well I use 5.38's with my 42's and I would think they would be way to much gears for 35's but hey what ever floats your boat.:rofl:

 

[Pedestrian]

I agree it is probably geared way lower than I would need. I usually only run pavement till I get to the trail, never drive it around town. I use the Bronco for camping and wheeling trips but am thinking of making it a dedicated off road toy.
I would prefer to run 37s but they are just not in the budget, and like I said I have the axles just sitting around. I guess I'll try it and see. Worst case I can just remove them and reinstall the 3.50s I hate.
Breakage is my biggest concern.

 

[jopes]

what are you afraid of breaking?

 

[thin blue line]

to much gear for 35's

 

[Pedestrian]

what are you afraid of breaking?

I've never run a locker in the front of anything I have owned.
I guess I am concerned about breaking ujoints in the front axles. I plan on trying some of the more extreme trails at this year's Bronco Stampede.
I have heard that 37s are about the limit for a 44 and I'm a little worried that with the torque multiplication I might snap stuff with the 35s.
Maybe I'm just being paranoid.

 

[rhauf]

lower gears will not necessarily CAUSE you to break axles more.. however, it will give you the ability to break an axle easier by giving it less gas.. if you know how to control your foot, the 5.38's will give you an advantage, and may even help prevent breaking stuff.
lower gear ratios will actually reduce driveline torque, so this makes your driveline U joints, trans, and transfercase stronger by better torque ratio.


the only downside i would see, is that without an overdrive, your going to be running very high rpm at road/highway speeds.
i have 5.38's and lockers in my explorer, with 37" tires. back when my overdrive wasn't working, i was running redline RPM down the freeway at 70mph.

 

[jopes]

half ton axles
+
5.38's
+
doubler
+
locker
+
35" to 37" tires.
=
BOOM

 

[Pedestrian]

Running the freeway isn't really a concern, I don't mind being the guy in the slow lane for 15 to 20 min to get where I need to be.

I am however worried that jopes may be right "Boom" I have a carbed motor and very little throttle control in the steep stuff.
I am gathering the stuff to convert to EFI but machining and welding the intake to accept injectors is beyond my skill level and budget at this point.

 

[OX1]

I'm running your effective overall gear ratio with 42's and I'm not complaining about needing more gear. You really think you need more gear or do you just want the lockers?

If you just want the lockers, I'd pull them and get some 4.10's, maybe 4.56's.
The 15 minute ride you say you will be fine with on 5.38's and 35's will happen maybe one or 2 times and you will be putting another gear in.

 

[rossisnow]

Assuming 30 in tires were stock, the 35's would be around 17% larger. 35/30= 1.167. If the truck had 4.56 gears to start, the 5.38 gear ratio would be about 18% lower. 5.38/4.56 = 1.18. Assuming the variables are true, you would just be returning the truck to the near stock setup. I dont know the effect of the doubler, not even sure what that is:doh0715:, or the locker, but the math seems ok.

rpm = mph x gear ratio x 336 / tire diameter

Put in the rpm's you want at whichever speed, and solve for gear ratio:

GR= (RPMxTire Size)/(MPHx336)

Smaller pinion = smaller teeth = bigger load distribution per tooth = be careful
Also, true tire height is twice the distance measured from the ground to center of hub. Usually knocks an inch or two off the ratio.....

 

[OX1]

Pretty sure he has stock 3.50 gears now.

Assuming 30 in tires were stock, the 35's would be around 17% larger. 35/30= 1.167. If the truck had 4.56 gears to start, the 5.38 gear ratio would be about 18% lower. 5.38/4.56 = 1.18. Assuming the variables are true, you would just be returning the truck to the near stock setup. I dont know the effect of the doubler, not even sure what that is:doh0715:, or the locker, but the math seems ok.

rpm = mph x gear ratio x 336 / tire diameter

Put in the rpm's you want at whichever speed, and solve for gear ratio:

GR= (RPMxTire Size)/(MPHx336)

Smaller pinion = smaller teeth = bigger load distribution per tooth = be careful
Also, true tire height is twice the distance measured from the ground to center of hub. Usually knocks an inch or two off the ratio.....

 

[rossisnow]

You would be going 63-68mph at 3500rpm with that ratio. 68mph = (3500rpmx35")/(5.38x336).

 

[Robs79BBbronco]

the 400 will be screaming at you....even doing 55.

 

[Pedestrian]

Thanks for the input, I think I'll just hold out for a 60 and a sterling and do it right the first time.