About to Start a Highly Ambitious Project - 91 Suburban

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by Crawdaddy, Apr 3, 2010.

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  1. Crawdaddy

    Crawdaddy Moderator Staff Member Platinum Contributor 1000 Posts 100 Posts

    Well, today I went on another successful trip to the junkyard, or at least mostly successful. I scored a GM Corporate 10-bolt front axle, leaf springs, transfer case crossmember and skid plate. It all came off a 1982 Chevy Blazer. Unfortunately, I didn’t get the spring hangers because they were riveted to the frame and I didn’t have anything to knock the rivets off with. I also didn’t get the engine crossmember because of the rivets. I also didn’t get a transmission or transfer case out of it because they weren’t there.

    For those of you that don’t know, 4x4 vehicles are very rare down in my neck of the woods. So, I’m trying to turn my half-ton 1991 2WD Suburban into a 4x4 ¾ ton truck so I can pull my 9000 pound camper. I don’t need 4WD on the Suburban, but I figured since I was swapping out the rear axle for a GM Corporate 14-bolt to help get my weight capacity up, I might as well work on the front end and make it into a 4x4.

    I have both axles. For the rear, I have a 14-bolt with 4.10 gears. I got it off a 1999 Chevy 1-ton SRW truck. I’m going to rebuild it fully, and will probably drop a Detroit locker in there while I’m at it. I think it has a 65” WMS to WMS width, which I think is the right width for the Suburban. For the front, I got a 10-bolt with currently unknown gears, but I’m sure it’s not 4.10s… that would be too easy. So, while I re-gear it, I’ll possibly add a traction-adder in, might as well. I still have not measured the width very accurately on this axle, but I’m hoping it’s the same as the 14-bolt. I think the Blazer and Suburban have the same track width.

    From what I understand, the older Blazers are essentially the same thing as a Suburban up until the B-pillar, so I figured the front end should just bolt up. Well, I’ve done some preliminary measuring and it does look like it will indeed bolt up to the front, but I will have to drill all my mounting bolt holes. The 80s Blazer and Suburban both use a solid front axle with leaf springs, and also appear to both use a 2-leaf spring pack. I thought that was a bit weird, and I may move up to a higher count leaf pack in the front to compensate for the perceived lack of weight capacity.

    I also need a transmission and transfer case still. I am going to go with a TH700R4 because it’s what I already have, but I need one with a short tailshaft to mate with the transfer case. I think I’m supposed to have either a NP241 or a NP208 transfer case, though I’m not sure which. I’m currently leaning towards that I’m supposed to have a NP241, though I may go with a NP208 since I already have one in the Bronco, and parts should at least partially work in both.

    Mounts. I will definitely need a new engine cross member because the 2WD cross member hangs down too low and would interfere with the axle and spring pack. I was hoping that I wouldn’t need it, but I don’t think I’m going to get away with this. Going to have to source this one out. I have the transfer case cross member, but I will have to drill holes for it on the frame rail. I also need to source the spring mounts. LMC has them, so that shouldn’t be a huge issue, but like all my other mounts, I’ll need to drill for them all.

    Steering is one thing that’s troubling me some. From what I can tell, there are 2 different steering boxes, one for 2WD, one for 4WD. However, I’m not sure what the difference is. I do know that this 10-bolt front axle uses a weird curved steering arm that converts forward and backward motion into left and right steering. Weird. I’m not sure why I can’t just rotate the center resting position of my current pitman arm 90 degrees and hook the linkage up, but from what I’ve read so far, I can’t. Anyone know anything about this?

    So, that’s where I am with this highly ambitious project and will be the biggest thing I’ve ever done on a scale of several magnitudes. Any comments or ideas are incredibly welcomed. Any help that can be locally provided is also greatly appreciated. I love this Suburban, and I hope to make it even better than it already is!
  2. pmartin816

    pmartin816 New Member 1000 Posts 100 Posts

    Wow you have your hands full. I don't think I can help but say good luck I hope it goes well. Looking forward to hearing about your progress.
  3. tbplus10

    tbplus10 Super Moderator Staff Member Platinum Contributor 1000 Posts 100 Posts

    You've got a lot of work ahead of you Christopher but I think with the parts you've sourced it should turn out to be a good swap.
    The older 2 leaf springs have a habit of sagging, I'm sure technology has advanced things enough so you should be able to find something with 3 or 4 springs that'll fit your application and not sag as much.
    If I remember correctly on the transfer case you can use either one, they both drop on the same side, there is a difference in the final gearing but I dont remember it being much, probably the lower geared will be the prefered one.
    If you can find a truck or Suburban in the same body style the frame should be able to give you all your measurements without any exotic algorithyms to get things close to factory.
    A 4x4 body can also provide measurments and panels for the trans tunnel mod you need to do.
  4. unplugged

    unplugged New Member 1000 Posts 100 Posts

    Wow. I admire your ambition. I know the work can be done, I just can't get the steam up for that kind of work anymore. Please take pics for those of who live vicariously through the adventures of others. It's not my habit to subscribe to threads, but this one is an exception. Best wishes on your project.
  5. murdog94

    murdog94 New Member 1000 Posts 100 Posts

    Good luck with it. and i agree take some pics. Id like to see how it goes..
  6. Allmostsmart

    Allmostsmart New Member

    Hey Man. I will be doing the same thing here pretty soon. You said you got the front axle from a Chevy Blazer? The problem with that is that all Chevy front ends are Passenger side differentials. Your NP241 I believe is a Drivers side differential. If you have a Chevy Front then I would look for a NP205. I will check on a NP208. It might be passenger side.
  7. Allmostsmart

    Allmostsmart New Member

    The Chevy NP208 is a Passenger side output for the front driveshaft so I think that will work just fine for your 10 Bolt.
  8. Crawdaddy

    Crawdaddy Moderator Staff Member Platinum Contributor 1000 Posts 100 Posts

    I know that NP241 and NP208 both came in passenger side drop, so that isn't an issue. The NP241 has a .1 higher crawl ratio than the NP208, but as previously stated, I think I'm going to lean towards the NP208 just so I can swap parts if neccesary with my NP208 in the Bronco.

    I figured someone made a higher leaf count leaf spring for the front. When I pulled the leafs off the Blazer, they were nearly flat from sagging so much. I just need to figure out what spring I need to get in order to hopefully keep the very smooth ride I currently have, though I think it's mostly a function of my existing springs sagging so much.

    I will do my best to put my hands on another 4x4 80s bodystyle truck for measurements, though I don't think I'm going to have a lot of success. Over 95% of vehicles sold in the New Orleans area are 2wd simply because we don't have a need for 4x4. There might be a 100 foot difference in the highest and lowest point in the area. :lol: I measured the Blazer leafs and they measure 46 inches long from eye to eye in their relaxed state. I then took the center of my existing front tires, and measured 23 inches fore and aft. To the front, it appears that the mounts would go right about where the radiator core supports are, which matches what I remember of the mounts on the Blazer. The rear mounts end up right around where the frame starts dropping to go under the cab, which is also consistent with my memory.

    Tim, this transmission tunnel mod you say I need to do, what do you mean? I thought everything was low enough that the transfer case would simply bolt in place and have clearances. If you're talking about for the transfer case shifter, I'm still working on what I will have to custom fab, because I have my center console there. I will have to fab some sort of shifter relocation bracket to move it. I also noticed that the existing exhaust will be directly in the way of the driveshaft going to the front axle, so I'm going to have to figure out how to relocate it to provide clearance.

    The goal is to simply provide a stock 4x4 Suburban. As most wheelers know, such a long wheelbase makes a Suburban useless for anything except possibly mudding because it's too long. I also don't plan to wheel this truck, so putting any heavier or custom axle up front simply doesn't make sense. As always, any guidance, tips, tricks, warnings, comments, are greatly appreciated. Like I previously stated, this is the first time I've ever tried anything beyond simple parts-changing. This is definitely going to involve fab work, which I have no skills in.

    Thanks!

    EDIT: This is that super-weird steering arm on the Blazer axle. What engineer came up with this? If it works...
    [​IMG]
    Last edited: Apr 4, 2010
  9. Crawdaddy

    Crawdaddy Moderator Staff Member Platinum Contributor 1000 Posts 100 Posts

    This thread up to now has been devoid of pictures, but that's going to change right now! So, without further adieu, here we go...

    Here's how the Suburban sits today. Bland, boring, in need of work:
    [​IMG]

    One major project I did to this truck was to build a custom wood center console to relocate and house the radio, and a carputer:
    [​IMG]
    [​IMG]

    Here's the 14-bolt axle I got off a 99 K3500 1-ton truck:
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    [​IMG]
    I've since wire-wheeled it in preparation for painting and rebuilding it.

    And here's the GM 10-bolt front axle I just got yesterday:
    [​IMG]
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    [​IMG]
    It's still sitting on the trailer I brought it home on because I haven't gotten anyone to help me offload it yet. It's not quite as heavy as the 14-bolt, but it's still heavier than 2 people can pick up together. As you can see, it's still got the leafs, sway bar, shocks, and steering components on it. The brakes are definitely shot, but they will get replaced anyway.

    Speaking of brakes and things on the end of the axle... I'm going to need to convert this axle to 8-lug from it's current 6-lug status. I've done some googling and everyone seems to be talking about how to convert a Dana 44 front to 8-lug. Unless, I'm not understanding them correctly, and from the spindles out the D44 and GM 10-bolt are the same, but that can't be, can it? I'm definitely going to have to somehow make this front match the 8-lug full-floating pattern the 14-bolt is going to have on the rear. Any ideas?
  10. tbplus10

    tbplus10 Super Moderator Staff Member Platinum Contributor 1000 Posts 100 Posts

    Yea the trans tunnel mod for the t-case shifter.
    It looks like you have an open area under your center console so you could bring the shifter up there then weld together an adaptor to bring it out by the drivers leg.
    The t-case is only a fore and aft throw shifter so it shouldnt be a big problem.

    The exhaust tube coming from the manifold has a sharp bend and the tube is semi fattened to clear the suspension. I'm pretty sure thiers a couple manufacturers that make headers for 4wd's that clear the suspension much better than the factory pipes did. Try Hooker, Pacesetter, etc.

    The axle outers have some bearing and tolerance differences, maybe a set of 6 to 8 lug spacer/adaptors would be the best way to go. I dont remember many people converting these axles to 8 lugs.

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