Gear Selection for a "street" 4x4??? - 4.10 or 3.73

[arkracing]

In the planning stages for a new project and need some opinions about gear selection.

I picked up a '72 K20 chassis with no axles. The plan is for a D60/14b FF axle combo.

This will not be a trail rig or mud rig or anything like that, mainly for towing a car trailer etc. I might put a plow on it as well. A Work Truck.

*I already have 2 Rear ends, one is a 14bFF 2wd with 3.73 gears & the Large brakes, the other is a 14bFF 4wd with 4.10 gears & the smaller brakes.
*I already have a D60 front with 4.10 gears, but it is a "drive flange" front end from a Fulltime NP203 truck, so the hubs would have to be machined so I could put Lockouts in it.
*I can get a D60 with 3.73 gears & lockouts for a reasonable price (IMO anyway)

*I Plan to run a 235/85R16 tire - or something close. So that would be around 31.7" or we'll say 32"
*Also plan on a TH400/NP205 combo behind a 350ci or 383ci.

What do you guys think I should run for gears the 4.10's or the 3.73's. I'd like it to have good towing power but not be screaming @ 65-70mph either.

Edit: Found a calculator, @ 65MPH with 4.10's and 31.7" tires I would be turning approx 2900rpm, with 3.73's it would be approx 2600rpm

What's your honest opinion?

Thanks!

(oh and what would my D60 4.10 Front end be worth if I decided to go with the 3.73 one instead? $500 or so??)

[Hottrucks]

what power if its a big block 3:73's if its a small block 3:73's since your in CT it's not like your going to pull any monster hills and you'll need the gear to run on 91

are they top pinion or bottom??

[snj8198]

i agree with hotrucks. i'd use the 3.73 with a big block or real torquey sb stroker, and definitely 4.10 with say a warm 350 and smaller. -steve

[arkracing]

Originally Posted by Hottrucks

what power if its a big block 3:73's if its a small block 3:73's since your in CT it's not like your going to pull any monster hills and you'll need the gear to run on 91

are they top pinion or bottom??

I assume that you mean 4.10's for a small block. I was thinking a Vortec headed 383 stroker - (small block with big block power).

The 4.10 D60 front is the standard low pinion axle. I thought maybe I could sell the D60/14bFF 4.10 Axle set together, and I also have a TH400/NP203 that someone who wanted to do an ORD doubler should be interested in. The TH400 was rebuilt recently and is in good shape.

[Stocker]

My K20 (350/350) has 4.10s. It's not bad at 55-60 mph, but if you will be doing any amount of 65-70 mph, I would honestly advise going with 3.73s. It'll be a bit less busy at higher speeds and may even help mpg just a little -- and you'll still have plenty of grunt for a work truck.

BTW, mine came stock with 7.50-16s and now has 33/12.50-16.5s, both ~32" tall.

[FormerMember]

I'd go 3.73's either way. Should be enough grunt.

Nice to see you posting again.

[arkracing]

Thanks for the input guys.

Grendel - I'm really sorry about not calling you back. I'll PM you with some more information.

[Hottrucks]

is the front a disc set up?? and what is the width and which side is the pinion ??? I need one for a ford and I want bottom loader with the pinion on the left.....for header clearance

[shakedown96]

I live in the catskill mountan reigion. my 71 has 3.73's and does verry well on the street I have towed with it, the PO towed insanely heavy loads with it. he showed me a recipt from the scrap yard scale that was around 12-13 thousand thats truck trailer and load. my truck has the sm465 granny low 4 speed with a 350 set up with a low rpm hi torque cam verry mild but runs well. I weighed out the option of the 350 vs 383 and for me it isnt worth the cash. theres a guy that does rebuilds at his machine shop and will do a 350 exchange short block for $650 the 383 was around $3000 all said and done.
I plan to install a nv4500 tranny in my truck and drive it daily. my tire size is 31's. good luck

here are some usefull links for gear questions

gm tranny ratios
http://forum.snoman.com/viewtopic.php?t=153

handy calculators
http://www.snoman.com/HTML/axlecalc_5a.html

[arkracing]

Originally Posted by shakedown96

I live in the catskill mountan reigion. my 71 has 3.73's and does verry well on the street I have towed with it, the PO towed insanely heavy loads with it. he showed me a recipt from the scrap yard scale that was around 12-13 thousand thats truck trailer and load. my truck has the sm465 granny low 4 speed with a 350 set up with a low rpm hi torque cam verry mild but runs well. I weighed out the option of the 350 vs 383 and for me it isnt worth the cash. theres a guy that does rebuilds at his machine shop and will do a 350 exchange short block for $650 the 383 was around $3000 all said and done.
I plan to install a nv4500 tranny in my truck and drive it daily. my tire size is 31's. good luck

here are some usefull links for gear questions

gm tranny ratios
http://forum.snoman.com/viewtopic.php?t=153

handy calculators
http://www.snoman.com/HTML/axlecalc_5a.html

Thanks for the info. I'll probably go with the 3.73's as I will be doing some limited highway towing as well.


Not that I recommend it, but I've had 12k rolling across the scales here, with my '94 1/2t Silverado 305/4L60E/3.42 geared truck. Of course that isn't through the Catskills, probably only about 10miles from my shop with the trailer brakes cranked up to the max.

[FormerMember]

Do you have a 383 already?

[arkracing]

No, I was thinking about buying a Balanced Assembly and having 1 of my 15+ 350 blocks bored .030 or .040 over. Then getting a set of Vortec heads for it.

First things first, picking up the 3.73 D60 front (& hopefully selling the 4.10 D60/14bFF)

[shakedown96]

I dont Know where you are in CT but a freind of mine had a 79 ford that he did some axle swaps on in torington at the raidiator shop on rt 4. just give Wayne a call he may swap you or know some one who would. pm me if you cant put that together.

[Dooley]

Originally Posted by arkracing

*I already have a D60 front with 4.10 gears, but it is a "drive flange" front end from a Fulltime NP203 truck, so the hubs would have to be machined so I could put Lockouts in it.

I don't see a problem here. I put Husky Heavy Duty Selectro hubs on my full time D60 in my 1979 K30 right out of the box.



I do prefer 3.73's on all my trucks that spend most of their time on highway.

[71blksuper4x4]

Too bad you don't live close to me, I would buy those axles from ya. Good luck with the sell. Trevor

[arkracing]

Originally Posted by Dooley

I don't see a problem here. I put Husky Heavy Duty Selectro hubs on my full time D60 in my 1979 K30 right out of the box.


I do prefer 3.73's on all my trucks that spend most of their time on highway.

I've heard that some of the Fulltime front ends that had factory drive flanges, do not have the groove machined for the outer snap ring that is utilized in lockouts.

I've made the decision to go with the 3.73's thanks to all your recommendations.

I have 2 options to get a D60 front with the 3.73's. 1 involves me buying it outright, and the other would be a partial trade (mine + cash). I think that I'm going to buy the one outright provided it is in good shape, and then sell my 4.10 D60/14bff as a set.

Thanks again - Andy

[FormerMember]

Originally Posted by arkracing

I've heard that some of the Fulltime front ends that had factory drive flanges, do not have the groove machined for the outer snap ring that is utilized in lockouts.

I've made the decision to go with the 3.73's thanks to all your recommendations.

I have 2 options to get a D60 front with the 3.73's. 1 involves me buying it outright, and the other would be a partial trade (mine + cash). I think that I'm going to buy the one outright provided it is in good shape, and then sell my 4.10 D60/14bff as a set.

Thanks again - Andy

A grinder will fix the axleshafts in about 2 mins.