1984 K20 axle swap to 1988 V10 suburban

[MuddiGGEr25]

I am going to the yard tomorrow morning and going to measure the leaf springs on a 1982 K20 with a 6.2l NP208, and 4.10 gearing.

I want to put them into my 1988 V10 suburban NP208 L05 5.7l tbi (not stock but dont have specs on build yet)

I know there are 2 different spring lengths 52" and 56"

I know the shocks were a larger diameter according to the book in the gm heritage center

From what i have read it should be a SF14 or FF14 for the rear and a gm 10 bolt in the front with the 8 lug setup

I know some people say the 3/4 springs ride harsh but i prefer a firm ride anyway and more than likely they are already worn a bit so it shouldnt be as bad as new.

I want to simply go out, disconnect the driveshafts, brake lines, shocks, and steering arm, pull the shackle bolts and drop them right into my trailer, does it get more complicated than that with these?

It has auto locking hubs, but since it is a gm 10bolt like my current 6 lug setup, will my manual lockers work?

Is there anything else I should know to look for, i.e. yoke differences, steering linkage differences, etc

I know i wont be a "full" 3/4 suburban due to frame differences, but my springs are sagging very low, my air shocks are blown out, and both of my 10 bolt axles are done for, plus the 4.10 ratio should help towing and offroad both. 3.42------>4.10

[hatzie]

I usually just cut the rubber brake lines.  I disconnect the e-brake cables if I can.  I'd pull the whole under truck E-brake cable setup including the frame hooks.

The front axle will bolt up. 

The rear of the Suburban frames is wider than the pickup frames.  Measure from the outside ends of the Burb spring perch for the extreme width and measure the width between the brake backer plates on your Burb. 
If the distance between the backer plates is too narrow it's a show stopper. 
You already know the spring perches are too narrow.  The reason to have the width on the perches is to see if there's room on the pickup axle tubes for the new perches.  You can move the spring perches and shock mounts out if there's room on the tube.  Perches and shock mounts are available from hardcore offroading outfits.  It'll take some welding.
https://www.google.com/search?q=weld+on+spring+perches
https://www.google.com/search?q=weld+on+shock+mounts

[roundhouse]

Grab the driveshafts too
And you'll need a pickle fork and a big hammer to remove the steering arm



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[MuddiGGEr25]

Ok I got the axles I measured and they are 56"springs but i will either get the proper perches or just put the axle on my existing 1/2 springs until i find a better option, bc i have a friend with many 2500's with the 14 bolt but not sure about the spring lengths.

Here is a link to all photos I have at the moment, my trailer is out at the junkyard until taxes when i can pay for the axles and get to work:
https://www.facebook.com/media/set/?set=a.10206985539569745.1073741832.1016864859&type=1&l=5f5788d01a

I removed the steering system entirely at the gearbox so i should just be able to line up the splines and tighten it down.

I currently have a 10 bolt 6 lug front with manual hubs, the donor is a 10 bolt 8 lug front with auto hubs, my quick measurements say this part will be the easiest since its the same gm10? it has the extra leaf for the 3/4 spring rate but overall same length as my current springs, also can the auto/manual hubs interchange without much work or am i stuck with autos now?

Donor and current T-Case are both NP208, so no issues there.

I was NOT able to salvage the rear driveshaft since the payloader bent it when flipping the truck over. so I will probably need a $#*() joint for the GM14 to use my existing axle for the time being, until i can find another 3/4 that hasnt been trashed yet

I had no choice but to use this 3/4 setup since i am low on funds, low on time, and there were no other complete 4x4 axles anywhere in the yard bc they have been cleaning out with the warm weather. I am only paying $75 for each axle, and rims with crappy tires are free lol.

I think i will be needing:

1 $#*() u joint for GM10 driveshaft to GM14 axle

2 Spring perches

2 Air shocks rear

??Possible shock mounts rear??? I havent checked locations yet

bleeding the brakes out so a good qt of DOT4, btw what is the proper "sequence"to bleed brakes after a procedure like this?

4qts of syn gear oil to refill both axles




So should i be expecting any other misc parts, I am getting fresh air shocks for the rear, and my current fronts are only a year or so old, they handle well, and the donor shocks were all done for in any case.

The tie rod appears bent to me but then again i was dripping wet and could barely walk by the time i got done.

I am sure ill think of something else but for now this should do it.

Thanks for not flaming me, I know there are numerous other threads regarding GM10 to GM14 swaps but I couldnt find anyone doing it to a suburban that has been swapped from 6.2 to 5.7 and 700r4 to th350. 

I will be attempting this swap on or around feb 5th and we have a charge acct through napa at the shop so I can have parts brought to me if i need them.

distance between backing plates leaves me atleast a good 6-8" iirc but i am not near them now

I measured from the outer edges of the springs, and from center to center on the springs and the width is an exact match for my springs, just 4 more leaves in the pack lol

PS took me 3.5 hours to pull both axles with nothing but hand tools, and a zawzall with 1 charge to cut the brakes and driveshaft.

[MuddiGGEr25]

Ok i knew i would think of something else, So ive been digging on here, chevytrucks.com, k5, and a few others i have only read about 60 forum pages so far and some of it was nonsense or no answer was given before the thread died/closed.

From what I understand I can purchase a shack flip kit like this one for example:GU38010 on:   http://www.offroaddesign.com/catalog/shacklekit.htm 

If i am understanding correctly I would use the grinder/ air hammer at work to knock out the rivets of the original 52"spring shackles, then mount these up in the 56"holes that are already there, the kit I specified would give me 4"of lift, in addition to whatever I get from the 3/4 springs ( I have heard the K20 and V20 has a stock 2"additional ground clearance) and I would simply attach the springs to the existing front hanger, and the above mentioned rear hanger. then just bolt up drive shaft, brakes, and shocks, and all that would be left is to bleed them?

It just seems to simple, I know it will be a PITA when i actually do it next week, but anytime things seem simple i am forgetting something.

PS front springs are same length/width but 3 leaves instead of 2.

Will my pinion angle be ok with a 4"shackle? or am i better off with the 2 1/2 to avoid further mods?

Is it possible at all to relocate existing shackle to the 56"set of mounting holes and just call it a day? or not sturdy enough for the 3/4 axle springs? or is there an adapter I can buy that will allow the 52" mounts to accept the 56" springs? I am not at all looking forward to lowering the fuel tank again yet, since the rivets are right behind it.

I would like to mount the 56" springs because my 1/2's are very worn, like really really sag even with a 2000lb helper and air shocks, but i am limited on budget and time so options are limited right now. I am not sure i am comfortable removing axle from springs and switching it that way, of course if i have no other choice I will do what i must but I want to find the most painless option overall.

ok rant done, lets hear some input from all you older guys and gals out there

[MuddiGGEr25]

I have a new question today, I am not entirely wanting to move my spring mount back since I will have to find time to squeeze it into the shop on the rotary lift, drop the tank shield, tank, and then go through the whole rig a maroll for removing the rivets, redrilling the holes @ 7/16" putting in all new hardware etc, etc. I was thinking of an alternative option that will allow me to do the swap in my driveway. If I remove the ubolts on the GM 14bolt, and remove the "top" spring with the eyes, and the next 1 or 2 so that the spring pack is shorter than the "top" spring on my 52" spring pack. Then take the "Top" spring from the 52" pack that is currently under the burb, bolt iton top of the rest of the 3/4ton spring pack and axle, with or without a block lift. If i am thinking correctly, this will enable me to roll the 3/4ton axle and my "new" spring pack right under the burb and just boltup without any modifications to the mount points. Does anyone see a problem with this idea? the 3/4axles came in a 52" variation so I would assume the "top" spring the 52" 3/4 pack to be the same as the "Top" spring in the 52" 1/2 pack. anyone correct me if i am wrong here, I verified the shocks are interchangeable between current frame and donor axles, the same shocks are available for both vehicles. I am planning on doing the front axle later today or both on monday if possible. I just wanted an opinion in case my spring pack idea wont work. I know i will lose some "capacity" by dropping 1-2 springs, and narrowing to the 52" spring but time is not on my side, i have no idea if/when i could get into the shop before wednesday sadly.

[hatzie]

I have a new question today, I am not entirely wanting to move my spring mount back since I will have to find time to squeeze it into the shop on the rotary lift, drop the tank shield, tank, and then go through the whole rig a maroll for removing the rivets, redrilling the holes @ 7/16" putting in all new hardware etc, etc. I was thinking of an alternative option that will allow me to do the swap in my driveway. If I remove the ubolts on the GM 14bolt, and remove the "top" spring with the eyes, and the next 1 or 2 so that the spring pack is shorter than the "top" spring on my 52" spring pack. Then take the "Top" spring from the 52" pack that is currently under the burb, bolt iton top of the rest of the 3/4ton spring pack and axle, with or without a block lift. If i am thinking correctly, this will enable me to roll the 3/4ton axle and my "new" spring pack right under the burb and just boltup without any modifications to the mount points. Does anyone see a problem with this idea? the 3/4axles came in a 52" variation so I would assume the "top" spring the 52" 3/4 pack to be the same as the "Top" spring in the 52" 1/2 pack. anyone correct me if i am wrong here, I verified the shocks are interchangeable between current frame and donor axles, the same shocks are available for both vehicles. I am planning on doing the front axle later today or both on monday if possible. I just wanted an opinion in case my spring pack idea wont work. I know i will lose some "capacity" by dropping 1-2 springs, and narrowing to the 52" spring but time is not on my side, i have no idea if/when i could get into the shop before wednesday sadly.

If the master spring is the same width and leaves below don't overhang then you're building a spring pack.

My Droid from orbit

[MuddiGGEr25]

I have a new question today, I am not entirely wanting to move my spring mount back since I will have to find time to squeeze it into the shop on the rotary lift, drop the tank shield, tank, and then go through the whole rig a maroll for removing the rivets, redrilling the holes @ 7/16" putting in all new hardware etc, etc. I was thinking of an alternative option that will allow me to do the swap in my driveway. If I remove the ubolts on the GM 14bolt, and remove the "top" spring with the eyes, and the next 1 or 2 so that the spring pack is shorter than the "top" spring on my 52" spring pack. Then take the "Top" spring from the 52" pack that is currently under the burb, bolt iton top of the rest of the 3/4ton spring pack and axle, with or without a block lift. If i am thinking correctly, this will enable me to roll the 3/4ton axle and my "new" spring pack right under the burb and just boltup without any modifications to the mount points. Does anyone see a problem with this idea? the 3/4axles came in a 52" variation so I would assume the "top" spring the 52" 3/4 pack to be the same as the "Top" spring in the 52" 1/2 pack. anyone correct me if i am wrong here, I verified the shocks are interchangeable between current frame and donor axles, the same shocks are available for both vehicles. I am planning on doing the front axle later today or both on monday if possible. I just wanted an opinion in case my spring pack idea wont work. I know i will lose some "capacity" by dropping 1-2 springs, and narrowing to the 52" spring but time is not on my side, i have no idea if/when i could get into the shop before wednesday sadly.

If the master spring is the same width and leaves below don't overhang then you're building a spring pack.

My Droid from orbit

Thats what i was thinking, so the "top" spring with the eyes at each end is called the "master" spring? just so were on the same page. if so, then yes they are the same width, and by removing the spring directly under the donor master spring, nothing will overhang.   I will be going to pickup some C-clamps tonight or tomorrow, will 6" ones do the job?  Also since the "custom" pack will now have 1 less leaf in it, I should be just fine compressing them with the original stud/bolt right? I need this to go quickly and seamlessly as i am doing it in my driveway and its 25F-30F out with 20-45MPH winds so i really dont want to fight it more than I have to.

[hatzie]

I have a new question today, I am not entirely wanting to move my spring mount back since I will have to find time to squeeze it into the shop on the rotary lift, drop the tank shield, tank, and then go through the whole rig a maroll for removing the rivets, redrilling the holes @ 7/16" putting in all new hardware etc, etc. I was thinking of an alternative option that will allow me to do the swap in my driveway. If I remove the ubolts on the GM 14bolt, and remove the "top" spring with the eyes, and the next 1 or 2 so that the spring pack is shorter than the "top" spring on my 52" spring pack. Then take the "Top" spring from the 52" pack that is currently under the burb, bolt iton top of the rest of the 3/4ton spring pack and axle, with or without a block lift. If i am thinking correctly, this will enable me to roll the 3/4ton axle and my "new" spring pack right under the burb and just boltup without any modifications to the mount points. Does anyone see a problem with this idea? the 3/4axles came in a 52" variation so I would assume the "top" spring the 52" 3/4 pack to be the same as the "Top" spring in the 52" 1/2 pack. anyone correct me if i am wrong here, I verified the shocks are interchangeable between current frame and donor axles, the same shocks are available for both vehicles. I am planning on doing the front axle later today or both on monday if possible. I just wanted an opinion in case my spring pack idea wont work. I know i will lose some "capacity" by dropping 1-2 springs, and narrowing to the 52" spring but time is not on my side, i have no idea if/when i could get into the shop before wednesday sadly.

If the master spring is the same width and leaves below don't overhang then you're building a spring pack.

My Droid from orbit

Thats what i was thinking, so the "top" spring with the eyes at each end is called the "master" spring? just so were on the same page. if so, then yes they are the same width, and by removing the spring directly under the donor master spring, nothing will overhang.   I will be going to pickup some C-clamps tonight or tomorrow, will 6" ones do the job?  Also since the "custom" pack will now have 1 less leaf in it, I should be just fine compressing them with the original stud/bolt right? I need this to go quickly and seamlessly as i am doing it in my driveway and its 25F-30F out with 20-45MPH winds so i really dont want to fight it more than I have to.

I'd replace the U bolts and the center bolt in the spring pack unless they are new.
You also want to make sure the master leaf has somewhere near the same overhang on the next leaf that you had on the next leaf down on the 1/2 ton axle.

Look over the leaves to be sure they aren't cracked.

Are the 3/4 ton leaves thicker?

My Droid from orbit

[MuddiGGEr25]

I have a new question today, I am not entirely wanting to move my spring mount back since I will have to find time to squeeze it into the shop on the rotary lift, drop the tank shield, tank, and then go through the whole rig a maroll for removing the rivets, redrilling the holes @ 7/16" putting in all new hardware etc, etc. I was thinking of an alternative option that will allow me to do the swap in my driveway. If I remove the ubolts on the GM 14bolt, and remove the "top" spring with the eyes, and the next 1 or 2 so that the spring pack is shorter than the "top" spring on my 52" spring pack. Then take the "Top" spring from the 52" pack that is currently under the burb, bolt iton top of the rest of the 3/4ton spring pack and axle, with or without a block lift. If i am thinking correctly, this will enable me to roll the 3/4ton axle and my "new" spring pack right under the burb and just boltup without any modifications to the mount points. Does anyone see a problem with this idea? the 3/4axles came in a 52" variation so I would assume the "top" spring the 52" 3/4 pack to be the same as the "Top" spring in the 52" 1/2 pack. anyone correct me if i am wrong here, I verified the shocks are interchangeable between current frame and donor axles, the same shocks are available for both vehicles. I am planning on doing the front axle later today or both on monday if possible. I just wanted an opinion in case my spring pack idea wont work. I know i will lose some "capacity" by dropping 1-2 springs, and narrowing to the 52" spring but time is not on my side, i have no idea if/when i could get into the shop before wednesday sadly.

If the master spring is the same width and leaves below don't overhang then you're building a spring pack.

My Droid from orbit

Thats what i was thinking, so the "top" spring with the eyes at each end is called the "master" spring? just so were on the same page. if so, then yes they are the same width, and by removing the spring directly under the donor master spring, nothing will overhang.   I will be going to pickup some C-clamps tonight or tomorrow, will 6" ones do the job?  Also since the "custom" pack will now have 1 less leaf in it, I should be just fine compressing them with the original stud/bolt right? I need this to go quickly and seamlessly as i am doing it in my driveway and its 25F-30F out with 20-45MPH winds so i really dont want to fight it more than I have to.

I'd replace the U bolts and the center bolt in the spring pack unless they are new.
You also want to make sure the master leaf has somewhere near the same overhang on the next leaf that you had on the next leaf down on the 1/2 ton axle.

Look over the leaves to be sure they aren't cracked.

Are the 3/4 ton leaves thicker?

My Droid from orbit

not thicker or wider, just more of them, and not worn out either, no cracks, and not really any pitting i can see.
new u bolts for certain, and new center pin if the store has it when i go in tomorrow, if they dont they i have no choice but to use the existing, bc i have less than 36 hours till my deadline, so my choices are limited

[MuddiGGEr25]

also will a 6" HD C-clamp do the job? its the biggest i can find in town

[hatzie]

The last master leaf I replaced I didn't use a clamp. 
I installed the new master leaf on the shackles. 
Then I put the new pin in the spring pack base and stacked the old leaves on it. 
Then I slowly lifted the axle up with a floor jack while keeping the locator pin lined up with the hole in the master leaf till the locator pushed through the master leaf hole.
Once that was done I jacked the axle up enough that the top plate and U bolts, washers and, nuts could be fitted.
You want to spin the nuts down till all four make solid contact without tilting the plate and then give em 2 full turns each with a box wrench in an X pattern.
When they start to feel snug finish the last X.

  (1)  (4)
|----X-------------------Axle---------------
  (3)  (2)

Go back and do the same on the other side then move on to torquing the U-bolts the rest of the way down.


#1 rule.  The service manual torque specs are for DRY bolts unless it specifically says it's for lubricated bolts.
If you use Never-Seize or oil on the U-bolts derate the torque by 40% or you will over-torque the bolts...  Eaxmple if the service manual calls for 107ft-lb and you used Never-Seize...  40% of 107 (.40 x 107) is 43 so your lubricated Torque is the Dry 107ft-lb minus your derate 43ft-lb = 64ft-lb.  The numbers I just rattled off are not out of the service manual they are an example.

Now that the axle is semi firmly attached on both sides...  get out the torque wrench and set it for 1/3 of specified torque and go all the way around the X, then 2/3 all the way around, and then full torque all the way around.  This should keep the plate from tipping and the U-Bolts from collapsing the axle tube.

[Blazin]

I have tightened U bolts from Camaros, to Kenworths. I tight them with an impact gun. ( really tight ) I have never collapsed an axle tube.
As far as stacking up the 3/4 ton springs under the half ton main leaf. You said the current springs sag bad. This means the main leaf is worn. I would use the entire 3/4 ton pack, maybe slip one, or two of the 1/2 ton leaves into the pack if you want a little extra load capacity.

[1967KaiserM715]

I think he said the 3/4 ton spring pack was the 56" version...which I thought was 1 ton only, but probably my memory is bad


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[MuddiGGEr25]

the donor is 56" which i do not have the resources in my driveway to deal with moving the brackets back, its is 14F here and i have been under this thing since 630, all i have left is 2 cuts to finish removing the drivers side ubolts, then a single cut to remove my overload bracket that is being stubborn. I have already prepped the GM14, the spring packs are removed and i removed the 56" master, and the one right below that. I will place what is left under the 52" master that is still attached to the burb, raise each one up, tighten down the center pins, then figure out how to attach the axle to the spring packs, bc I have now broken my heavy duty 1/2 drive rachet and my good 3/8 which until tonight never failed me. my impact is getting weak, add that with a 1/4 line (no i do not have access to a 3/8) and the 14F temps just make any airgun complain up here.and i believe its quiet time already but im going to make my cuts in about 5 minutes and hope the cops dont get called. I am supposed to be leaving by 9AM. so i kinda got a crunch here, and no access to a secondary vehicle to run for parts.