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looking to upgrade rearends on my 89 k5 blazer, help needed

J

jaybuller

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Location
Natchez, ms
Hello, i just finished my 4bt cummins/nv4500 swap and now i want to swap out the factory 10 bolt rear ends for somthing better. My rear 10bolt has seen better days and it leaks like a siv and have way to much backlash in the gear set! so here what i do with the truck..... it is a daily driver with around 500 ftlbs of tourque, 33x12.50 tires that i also offroad with. My rear end ratio i want is 3.42 to 3.73 max. i want it to have low rolling resistance so i can continue to get 28 mpg so i was thinking somthing newer also would like to keep my 6 lug wheels if possible. What would you gusy recomend i through in it that is cheap, easy to come by, and an easy swap. I dont mind relocating shock brackets or spring perches but i dont want to get into narrowing or swapping axels out... some help on what the best pinion angle would be apreciated as well. Right now my stock 10 bolt angle is paralell with the deck so not pointing at the tranny output shaft at all. I also have a 3" lift...

Thank you Guys for any help....
Jay Buller
 
14 bolt from a newer (90's) half ton will have 6 bolts and be as strong as you can get
 
Aside from doing the infamous 14ff swap along with 8 lug wheels your next best bet would be a 14sf out of the newer trucks but you will have to move perches and shock brackets. I don't know what gears came factory in them so you would need to check that out but i'm sure 3.73's would be an easy option.
 
thanks guys, so the 14 sf with 6 lugs would hold up under lots of tourque and twisty trails? in stock form? thanks for the help i will look tomarrow at the local pick yards to see what they have availible. Any i dea if my stock brake lines and ebrake cables will work with these newr body style rear ends? thanks
 
14 b SF 6 lugs are pretty strong axles, it should handle your torque with out any issue at all.

They are very strong axles for a semi float axle.

Only other way to get 6 lug is adapters ( have to be custom made) on a 14 b or 70 or expensive custom hubs
 
thanks,, so how bout my options with the front? any strong 6 lugs out there easy to swap that will hold up good? my 10 bolt is perfect cond with new upper/lower ball joints and such and it is nice but i dont know how much abuse they can take also dont know how well they hold up with extra weight over them... the 4bt weighs about as much as a 454 big block.
 
The front axle unless you go with a D60 are basically all the same strength given 6 or 8 lug (D44 or 10 bolt).
 
ok thanks so through all the searching through this site it looks like everyone swaps in the d60 up front.... is there a lot of d44s and 10bolts that are breaking out there? i would like to make this thing bullet proof just bulletproof on a budget! if you know what i mean. 6 lug axels arnt a have to have just thought it would be nice. How bought 8 lug stuff out there? any good 8 lug rear swaps? also what d60 do i want to look for if i decide to go that route? ford 60s or chevy? what years to stay away from and what years to look for? thanks yall.
 
For rocks n lockers the 60 is the only way to go. For the mud runner/ mud drag world they all go for the d44 over all others:dunno: They seem to hold up well for them in the slop. 1400 plus hp
 
Hummm, i dont do rocks my truck is to purty for those!! i do a little mud and mostly dirt two track trails rutted out but no rock climbing for me. yall think my 10 bolt up front will be set? im was more worried about the 750 lb cummins hanging over it than the actual power snapping a shaft! like mabey the 10 bolt axel tubes arnt enough to support it and might sag over time or somthing.... i would love to keep my 10 bolt up front just from a money standpoint but also dont want to drive this thing out to my brothers house in pukes peak colorado and have to break a front axel and not be able to drive it back home to michigan!
 
jaybuller said:
Hello, i just finished my 4bt cummins/nv4500 swap and now i want to swap out the factory 10 bolt rear ends for somthing better. My rear 10bolt has seen better days and it leaks like a siv and have way to much backlash in the gear set! so here what i do with the truck..... it is a daily driver with around 500 ftlbs of tourque, 33x12.50 tires that i also offroad with. My rear end ratio i want is 3.42 to 3.73 max. i want it to have low rolling resistance so i can continue to get 28 mpg so i was thinking somthing newer also would like to keep my 6 lug wheels if possible. What would you gusy recomend i through in it that is cheap, easy to come by, and an easy swap. I dont mind relocating shock brackets or spring perches but i dont want to get into narrowing or swapping axels out... some help on what the best pinion angle would be apreciated as well. Right now my stock 10 bolt angle is paralell with the deck so not pointing at the tranny output shaft at all. I also have a 3" lift...

Thank you Guys for any help....
Jay Buller
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Stick with late model 14bolt sf. My friend has a scout with same tires and Cummins 4bt on dana 44's and they seem to be holding up alright. Courous about the torque you are getting (500 lb-ft) seems pretty high for a 4BT. Are you running a P-pump and injectors? If you are running that much torque and plan on wheeling it in rocks you may want to use a 14 bolt ff with a 6 lug hub conversion: https://www.4wdfactory.com/store/products.php?product=Solid-Axle-5-and-6-Lug-GM-14-Bolt-Wheel-Hubs
They are not cheap, but it maybe the best overall value when you consider strength and the cost of lockers. The weight would be the only downfall. I have been runnng my cummins 4BT with a TH475 and one tons and it gets around 21 mpg in town. I suspect my MPG lost is primarily due to drag (lift and 37's) and not having a lock up OD transmission. I would not worry too much about friction of a 14ff vs. 14sf. For your driveline angle I would keep it parrallel within 4 degrees if you are keeping the same driveline. One thing you may have to do is replace the lower 1310 ujoint with a 1310/1350 hybrid to run a 14 bolt ff or find a 3/4 ton driveline and shorten it.

Do you have a build page? Would like to check it out!
 
I had a torquey 454 4-speed in my old 84 that I built up. Had a Dana 44 up front, 4.10s and 35s, didnt' wheel hard, but never had any issues. Get a 10 bolt from 88-91 K-5 or burb, they have little bit bigger axles, but I think even an older one would be fine with what your doing.
 
thanks, yeah mine is an 89 k5 so the 10 bolt i have should be the bigger one? anyways, i have a build page but it is over on 4btswaps.com under the conversion section.... yeah im runnin a ppump 4bt with 181 dv;s in it and some 5x10 injectors from sdx, the fuel plate is gone and the afc spring is heated and stretched also timing is bumped up to 16.5*/ it runs good i havent dynoed it or anything but i had a 97 didge 12v that i dydnoed back a couple years ago that was 495hp and 927 ftlbs and this 4bt seems like it runs almost as good so im guessin it is around 500 mabey a tad more im thinkin its around 300 to 350 hp too but that is all with seat o the pants guess and this k5 is a lot lighter than my old 97 dodge...
 
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heres a couple picks for you folks that are curious...
 
big block approaches 700 lbs, plenty of big blocks out there that are pushing an honest 500 lb ft of torque.

The real question about the front axle is this, gonna run a front locker? If not stick with the 10 bolt hell with 33s I would stick with the 10 bolt anyway locker or not.

If you are worried about it bending truss it.

I have seen a couple guys running 10 bolts in the front on a big block trucks with 36s and 38s with no problems other than wearing out the ball joints, but those tires are way bigger than yours.

BTW I love your truck, I have read through the build thread over on 4bt swaps.
 
x2 on the front 10b holding up to your tire size and how you use it.

For the rear you can't go wrong with the 14b semi float. It's a 9.5" ring gear with pretty big 33 spline axles. Find one with 6 lugs and drum brakes and you can hook up your original parking brake cables. 88-98 1/2 ton Z71 or towing pack trucks should have the 14bsf. Also the light duty 2500s with 6 lugs should have the 14bsf.
 
jaybuller said:
thanks, yeah mine is an 89 k5 so the 10 bolt i have should be the bigger one? anyways, i have a build page but it is over on 4btswaps.com under the conversion section.... yeah im runnin a ppump 4bt with 181 dv;s in it and some 5x10 injectors from sdx, the fuel plate is gone and the afc spring is heated and stretched also timing is bumped up to 16.5*/ it runs good i havent dynoed it or anything but i had a 97 didge 12v that i dydnoed back a couple years ago that was 495hp and 927 ftlbs and this 4bt seems like it runs almost as good so im guessin it is around 500 mabey a tad more im thinkin its around 300 to 350 hp too but that is all with seat o the pants guess and this k5 is a lot lighter than my old 97 dodge...
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I have been looking all over for a p7100 do you know of any good sources? Sorry to get off topic. Build looks awsome!:waytogo:
 
Yeah theres a guy out near kansas city, mo that i bought my ppump motor from, hes got a few more... He sells em for around 3500 shipped. As far as just buying the ppump and al the related swap parts it will probly run just about as much. i seen a few for sale on comp diesel just the pump was 1800 dollars.
 
jaybuller said:
Yeah theres a guy out near kansas city, mo that i bought my ppump motor from, hes got a few more... He sells em for around 3500 shipped. As far as just buying the ppump and al the related swap parts it will probly run just about as much. i seen a few for sale on comp diesel just the pump was 1800 dollars.
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If you could PM me his info I would really appreciate it!
 
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