What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

Thinking about regearing...

CaneyCat

CaneyCat

Registered Member
Joined
Jun 14, 2013
Posts
84
Reaction score
12
Location
South Texas
I have been tossing around the idea of swapping out my stock 10 bolts that have 3.42s for a 10 and a 12 bolt with 3.73/4.10s. If I do the swap I would probably go for the 4.10s. I was wondering if anyone could give me some numbers on what I might see for gas milage, right now im getting around 12mpg with the stock 350tbi/700r4/3.42s with 265/75 BFG M/Ts. This is my daily driver and I only do mild mud/beach rides(mostly mud) with friends maybe once or twice a month if we all can get off work on the same days. I might start doing a little stock class mud racing also, nothing hardcore as I have to drive it to work on Monday and it is wayyy to clean to be ragging on it, I'll probably never lift or trim the finders so 1/2 ton axles will do all I need it to do. Any help Would be appreciated!
 
I had 31" tires, 700r4, and 3.73s for a while. I think that combo felt great on the road, both city and highway driving. It handled off roading well too, even with a very tired 350. Once the 400sbc went it, it felt super great lol

I say, for a once in a while off roader, 3.42 and 3.73 gears work nicely. What diameter is your tires, measured that is? And have you tried the gearing calculator?

With my current set up, I'm getting 10.5-11.5 mpg (all highway)

400sb, FAST EFI, 700r, 60/14, 4.88, 38x15.5"
 
Im running 305cid, 700r, 33 x 12.5 and 4:10gears. This is a very good compromise for me atleast. Im running 1900rpm @ 65mph.
 
3.42 to 3.73 is not a huge difference...I'd go 4.10...oh wait, I did...in my old 2 wheel driver...it was spectacular, to paraphrase Terri Hatcher.
 
Go 4.10 and you may see a raise in mpg. The engine won't have to work so hard to do the same work. Around town it will be much better as well. Long trips over 55 you will be higher in the rpm but not enough to make you lose much mpg. Maybe only raise it 4-600 rpm. It will also help your trans live longer and won't hunt for od.
 
chulisohombre said:
Go 4.10 and you may see a raise in mpg. The engine won't have to work so hard to do the same work. Around town it will be much better as well. Long trips over 55 you will be higher in the rpm but not enough to make you lose much mpg. Maybe only raise it 4-600 rpm. It will also help your trans live longer and won't hunt for od.
Click to expand...

Yeah thats why I was wanting to go with the 4.10s. I have a 45 min one way drive to work everyday that is 60/65 mph doing the speed limit except one short part through a small town thats 35 mph. I seem to get the best mpg at around 1850 rpms which is about 70 mph and I think thats about where i think i'd be with 4.10s doing the speed limit, right now 60 mph is 1600 rpms and 65 is 1700. Speedo is broke so I drive it by the tach lol
 
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...
 
Thanks guys, I'm really thinking that this is something that I want to do even more now. This leads me to my next question what is a good price I could expect to pay for a set of axles?
 
its been said many times over if you have overdrive go as deep as you can basicly.

700r4 love and work better with deep gears if you ever plan on realy using overdrive gear . this way the tranny dosnt cycle in/out of overdrive and lock/unlock the conv.
 
The last couple I bought were a couple hundred apiece. You can usually get a set of half tons under 500. 3/4 for 600 or so and one tons can go anywhere from a 1200 on up depending on where you get them and the condition of them. That's about as cheap as they get but you have to shop around if you want a good deal.
 
chulisohombre said:
The last couple I bought were a couple hundred apiece. You can usually get a set of half tons under 500. 3/4 for 600 or so and one tons can go anywhere from a 1200 on up depending on where you get them and the condition of them. That's about as cheap as they get but you have to shop around if you want a good deal.
Click to expand...
Ok cool, that's not too bad.. I also have a rifle I might could post on CL or something and see if anyone might want to trade their axles for my rifle.
 
Some people think their parts are worth their weight in gold so just don't jump on the first set of 2 grand halfton axles you see. Sometimes you can get a whole parts truck for the price someone wants for axles. You can take what you need and either resell it or scrap it if its not in great shape.
 
They can be cheap, just depends what your area is like. Here everything is made of gold :rolleyes:

I'm rocking 3.08s :doah: I'd be happy with 3.73 with my 33sx700r4. 4.10 would be great. Mine's a dual purpose DD/toy.

Maybe I missed it, you sticking with those 265s/31in or whatever? In that case I'd shoot for the 3.73 over a 4.10. I crawl the snot out of my setup with 3.08 and I'm uber undergeared, granted I stay in 4lo. And I do fine. Only complaint with my ratio is driving up a steep hill on roads, and 45mph speed limits cause the 700r4 to search for OD, one day I'll get around to swapping axles.

IMO you'd be happy with 3.73, I'd stick with that with your DD/highway use. 4.10 if you did less DD'ing, more playing but you don't, this opinion is based on you keeping those 31s and it being a DD, if you shot up to 33s I'd lean towards the 4.10.

Good gravy 12mpg. I forget what you gassers get :D ... nah I don't, I used to get 8mpg in Nom Nom. If most of your DD driving is highway speeds to work, I don't foresee a significant mpg drop moving to 3.73 or 4.10, you're in OD during those times anyway. And what'll you'll loose in higher RPMs on the highway, you may gain in working the engine less in city driving, like mentioned before.

chulisohombre said:
It will also help your trans live longer and won't hunt for od.
Click to expand...

Yeah this.

With his specs seemingly stock, it shouldn't be hunting with 31s. Mine does with 33s, but only right at 45mph, so I try to go 47 or so if I'll be driving for a while at that speed, or 43 if it'll only be for a little while. I think if I put 31s back on it wouldn't hunt like it does now, and I could get my azz up a hill a little easier :haha:
 
Last edited:
4.10 1/2-tons can be hard to find. Easier to find lower gears in 3/4-tons.
 
mrschaeferpants said:
I'm rocking 3.08s :doah: I'd be happy with 3.73 with my 33sx700r4. 4.10 would be great. Mine's a dual purpose DD/toy.

Maybe I missed it, you sticking with those 265s/31in or whatever? In that case I'd shoot for the 3.73 over a 4.10. I crawl the snot out of my setup with 3.08 and I'm uber undergeared, granted I stay in 4lo. And I do fine. Only complaint with my ratio is driving up a steep hill on roads, and 45mph speed limits cause the 700r4 to search for OD, one day I'll get around to swapping axles.

IMO you'd be happy with 3.73, I'd stick with that with your DD/highway use. 4.10 if you did less DD'ing, more playing but you don't, this opinion is based on you keeping those 31s and it being a DD, if you shot up to 33s I'd lean towards the 4.10.

Good gravy 12mpg. I forget what you gassers get :D ... nah I don't, I used to get 8mpg in Nom Nom. If most of your DD driving is highway speeds to work, I don't foresee a significant mpg drop moving to 3.73 or 4.10, you're in OD during those times anyway. And what'll you'll loose in higher RPMs on the highway, you may gain in working the engine less in city driving, like mentioned before.
Click to expand...
For now I am sticking with the 31s, I want bigger/wider tires but they were almost new and free(about 4k on them) so I could not really complain lol When I replace them it will be with some 31x12.50/32x11.50 or maybe even some 33x12.50 if I can bring myself to cut the fenders if needed.

Blue85 said:
4.10 1/2-tons can be hard to find. Easier to find lower gears in 3/4-tons.
Click to expand...

This I know but I was just wanting to stick with the wheels I have as I just bought the 16'' rims to put the tires I salvaged off my wrecked 98 Z71 on my blazer.
 
As stated above a pair of 1/2 axles with factory 4.10 gears are few and far between, if they even exist (I know you could find 4.10's on newer IFS trucks....both my dad and bro-in-law had 1500s made in the early to mid 2000's with these gears). 3.73's were fairly common but not sure I would spend much money or time just to go to this from 3.42, but some sort of upgrade otherwise in the axle strength would make it worthwhile.

I ran 32x11.50 on 3.73 and 33x12.50 on 4.10 in my 700r4 K5 and thought that was a pretty good ratio for daily driving.
 
I just pulled out my 3.73 axles and placed in some 3/4 ton suburban axles with 4.10's in them. If you were closer, we could strike up a deal! My front is torn down to the spindles but your existing parts would swap over. And my rear has newer seals, bearings and brakes.

Also, with your year (89), I think there is a front axle shaft spline difference (27 vs 30). Finding a 89 and up has the higher spline count and more desirable (it may go down to 1987 too, just don't remember).

Check your local junkyards too. All you are looking for are 3.73 axles in either suburbans, blazers or pickups (1/2 tons of course). I never did find any 1/2 ton axles with 4.10's in them. My cost at local pick and pull is about $110 per axle (with core in there). So, it's a good deal!

I'm running 35" tires and have noticed a little more pep in the 4.10's compared to the 3.73's.....nothing life changing, but slightly better. I'd think that 31" tires with 3.73's is going to be great for you.

My rpm's are around 1800 at 65 MPH. Not bad for 35" tires and 4.10 gears. My 700r4 is much happier now and does not hunt around near as often.
 
6.2Blazer said:
As stated above a pair of 1/2 axles with factory 4.10 gears are few and far between, if they even exist (I know you could find 4.10's on newer IFS trucks....both my dad and bro-in-law had 1500s made in the early to mid 2000's with these gears). 3.73's were fairly common but not sure I would spend much money or time just to go to this from 3.42, but some sort of upgrade otherwise in the axle strength would make it worthwhile.

I ran 32x11.50 on 3.73 and 33x12.50 on 4.10 in my 700r4 K5 and thought that was a pretty good ratio for daily driving.
Click to expand...

Do you happen to remember your gas mileage and did you have any lift?
 
You must log in or register to reply here.

Latest Posts

Top Bottom