Axle swap for gear ratio

[fallguy]

Ok fellas, here's my plan. I have an '86 K10 with new 350 (290hp) and 700R4 tranny. Currently I run 33" tires on 15" rims with a 2.5" suspension lift. My gear ratio is 3.42. WHen i run down the highway its constantly shifting to accomodate for the slightest of inclines...i hate that. really sucks down the gas when its always shifting down. Take it out of OD and it doesnt shift, but sucks down the gas....i know...ignore the gas guzzling 350 comments.

I want to steal axles out of 3/4 ton with 4.10 gears and lockouts. It'd be a direct swap I'm sure, but are the 4.10's too much or should I be looking for 3.73's? I am thinking this will actually help with fuel economy and not having to shift so much...or am i dreaming the impossible dream?

I will be putting in a 4" lift with 35" tires so that is the reason for my swap thought, or if i kept it where it sits, I know a 3.73 would most likely be perfect.

Thoughts?

 

[Driver4r]

When i go up to 35"s im going to go with 4.88's.
But right now you would be ok with 3.73's for gasmilage.

But 4.11's and a .7:1 OD on 35's will be around 1700rpm which i think is to low.
So 3.73/4.11's are ok for your current setup. But a lift and OD i would preffer 4.56/4.88

 

[HotRodPC]

You've got the right idea. Hell NO, go 4.10's !!! You're running a 700r4, even 4.56's would be good. 4.10's used are pretty common and if you're running any kind of tire over OEM size, like 33's and 35's x 12.50 you need all the gear you can get. GO 4.10's without doubt.

 

[Driver4r]

You've got the right idea. Hell NO, go 4.10's !!! You're running a 700r4, even 4.56's would be good. 4.10's used are pretty common and if you're running any kind of tire over OEM size, like 33's and 35's x 12.50 you need all the gear you can get. GO 4.10's without doubt.

I didnt see that he was running 33"s.
I figured it was still the factory 31"s or 235's.

 

[GreaseDog]

Don't waste your money swapping to 3.73 axles. If you are going to do it, go 4.10 or don't touch it.

 

[crazy4offroad]

At LEAST 4.10, and if you have plans to go bigger even just 35s I would go ahead for 4.56. Your trans will thank you later.

 

[bucket]

At LEAST 4.10, and if you have plans to go bigger even just 35s I would go ahead for 4.56. Your trans will thank you later.

Yepper!

 

[HotRodPC]

Old thread got woke up, and this maybe done by now. But just to add, I also agree 4.56 would be even better IF you're paying for a gear swap, buying gears and the whole 9 yards. And for sure the 700r4 will love you for it. Prolly the only way I'd consider 35's with a 700r4 is 4.56 or lower. I wouldn't have a problem with a Th350 running 35's and 4.10's though.

I many times suggest 4.10's cuz I know they are commonly found in used axles and can be gotten cheap. I've seen pairs of axles for $200-$250 ready to install and run. Of course they have 100,000-150,000 miles on them but still useable.

 

[fallguy]

Axles as received

 

[fallguy]

Ya...for real...lots of scraping!

 

[fallguy]

No bueno! Add new lockouts to the list.

 

[fallguy]

Wire wheel on a grinder and dust mask/protective glasses....and patience....all dust shields, rotors, hubs and axles are rust free ready to be wiped down with parts cleaner and primed.

Hubs are getting new races, bearings and seals pressed in at machine shop.

 

[fallguy]

Everyone primed and painted with engine paint.

 

[fallguy]

Painted Dana 44...didn't bother with diff cover...that'll be a new aluminum one some day.

 

[fallguy]

Painted Corp 14...same story with diff cover.

Waiting on finished hubs, new lockouts, new drums, turned rotors, lug studs, new calipers, new drum brakes...then reassembly!