Thinking about regearing...

[82355]

I have seen one set of stock half ton axles with 4.10's. They are under my brother's 1976 K5 Chalet. 3.73's are fairly common, but most of the pickups seem to have 3.08's.

A set of 3.73's, would be a step in the right direction.

Martin

 

[6.2Blazer]

I had a 6.2 diesel so really not comparing apples to apples for fuel economy. It did average 18 mpg with 32's and 3.73's at stock height and that was a majority of intown and backroad driving when I was teenage (i.e. foot to the floor always).

Nice to hear of a confirmed 4.10 1/2 ton axle sighting...makes sense you could get these in an old Chalet, but also goes toward how rare they are.

10-bolt fronts up to around '88 or '89 had 28 spline axle shafts just like the rear. In '88 the new body style trucks (IFS) got 30-spline rear 10-bolts and I would guess the K5's and Sub's kept the front 28-splines until they supply ran out, then went to 30-spline just to avoid having different carriers front and rear. My '90 had 30-spline front shafts. With that said I really wouldn't consider it an upgrade as the inners had a necked down portion near the splines that was basically the same as the 28-spline versions, and spares are fairly hard to find in the junkyard simply because of the low production run of these.

 

[CaneyCat]

Yeah guess I should have looked at your name first lol

 

[82355]

I have a set of 30 spline axle shafts out of a blown up ten bolt rear from a 1989 K5. It had an NP241 with a mechanical speedometer. I have the matching ten bolt front, but I haven't checked what spline count they are.

Martin

 

[CaneyCat]

How much more common are 4.10s in a 3/4 ton? I know I spent about 3 months looking at trucks this year, both new and old(98' being the newest I was looking at) before I found my K5, most being 1/2 ton but didn't find anything with 4.10s. If I did step up to 3/4 ton running gear I could use it as a way to justify getting the tires I want On the new rims haha!

 

[82355]

Very common.

Martin

 

[clandr1]

I switched from 3.42 to 4.10 and it really made a big difference on the highway. my 700r4 didn't go in and out of OD constantly. I'm stock, running 33x10.5 with a 350TBI. My average gas mileage is around 12, but I tend to be a little heavy footed. Best mileage I got after going to 4.10 was almost 16mpg on a road trip from TX to CO.

 

[CaneyCat]

I switched from 3.42 to 4.10 and it really made a big difference on the highway. my 700r4 didn't go in and out of OD constantly. I'm stock, running 33x10.5 with a 350TBI. My average gas mileage is around 12, but I tend to be a little heavy footed. Best mileage I got after going to 4.10 was almost 16mpg on a road trip from TX to CO.

Thank's for the info, i'll be on the hunt for some axles soon!

 

[Big Ray]

you'll have an 2.87 effective gear ratio with 4.10's in od...

(4.10 x .7)

3.42 comes out to 2.39...no wonder the old TBI truck was a dog on the highway...

I switched from 3.42 to 4.10 and it really made a big difference on the highway. my 700r4 didn't go in and out of OD constantly. I'm stock, running 33x10.5 with a 350TBI. My average gas mileage is around 12, but I tend to be a little heavy footed. Best mileage I got after going to 4.10 was almost 16mpg on a road trip from TX to CO.

+1


In my post above the old truck I was referring to was my old 89...sorry for any confusion...

1/2 tons with OD should have come with 4.10's, they run sooooo much better. On and off the highway

 

[6.2Blazer]

How much more common are 4.10s in a 3/4 ton? I know I spent about 3 months looking at trucks this year, both new and old(98' being the newest I was looking at) before I found my K5, most being 1/2 ton but didn't find anything with 4.10s. If I did step up to 3/4 ton running gear I could use it as a way to justify getting the tires I want On the new rims haha!

I would say that 4.10 was the most common gear ratio for 3/4 ton trucks, especially those with 14FF rear axles.

 

[82355]

I would say that 4.10 was the most common gear ratio for 3/4 ton trucks, especially those with 14FF rear axles.

That is my experience as well. With 3.73's being fairly common as well, and 4.56's actually being fairly rare.

Martin

 

[chulisohombre]

Most 3/4 ton I've seen are 3.73 or 4.10 gears. Newer half tons are usually under 3.73 gears because of the need for better fuel economy. You will find that pre 85 axles had higher gear ratios in the 3.73 to 4.56 range. Getting one ton cucv axles will cost you a couple grand but came with 4.56 gears and a rear Detroit locker. Most also had low mileage as well so wouldn't need much more than seals and maybe move spring perch to be ready to run. 3/4 ton and 33s will pretty much last the life of the truck if you can find a good set in 4.10 ratio. Mine was off a 82 pickup with 4.10. It was definitely noticeable from my 3.73 stock gears.