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  1. #1

    Default About to Start a Highly Ambitious Project - 91 Suburban

    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 didnít get the spring hangers because they were riveted to the frame and I didnít have anything to knock the rivets off with. I also didnít get the engine crossmember because of the rivets. I also didnít get a transmission or transfer case out of it because they werenít there.

    For those of you that donít know, 4x4 vehicles are very rare down in my neck of the woods. So, Iím trying to turn my half-ton 1991 2WD Suburban into a 4x4 ĺ ton truck so I can pull my 9000 pound camper. I donít 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. Iím going to rebuild it fully, and will probably drop a Detroit locker in there while Iím at it. I think it has a 65Ē 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 Iím sure itís not 4.10sÖ that would be too easy. So, while I re-gear it, Iíll possibly add a traction-adder in, might as well. I still have not measured the width very accurately on this axle, but Iím hoping itís 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, Iíve 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 itís what I already have, but I need one with a short tailshaft to mate with the transfer case. I think Iím supposed to have either a NP241 or a NP208 transfer case, though Iím not sure which. Iím currently leaning towards that Iím 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 wouldnít need it, but I donít think Iím 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 shouldnít be a huge issue, but like all my other mounts, Iíll need to drill for them all.

    Steering is one thing thatís troubling me some. From what I can tell, there are 2 different steering boxes, one for 2WD, one for 4WD. However, Iím 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. Iím not sure why I canít just rotate the center resting position of my current pitman arm 90 degrees and hook the linkage up, but from what Iíve read so far, I canít. Anyone know anything about this?

    So, thatís where I am with this highly ambitious project and will be the biggest thing Iíve 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!

    1991 Chevy Suburban 1/2 ton 2WD w/ chevy SBC 350-3/4 ton drivetrain upgrade w/4.10 gears 200K miles
    2005 Saturn ION-2 Stock 277K miles
    1982 Bronco, 1993 Bronco (sold), 1971 M35A2 Deuce and a Half

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  2. #2


    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.

    1987 Chevy Suburban
    5.7 350 with Edelbrock Cam and Intake
    32x11.5x15 tires
    True Dual Series 40 Flowmaster exhaust
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  3. #3


    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. #4
    Legend unplugged's Avatar
    Join Date
    Sep 2006
    High Deserts of SoCal


    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.
    There is no way to happiness....happiness is the way.:yipi:  _vXMYypuKMJFw671uF2ZPhjez_j-atRmcjM2zQKpQi1JSsB75/burb1.JPG
    High Desert SoCal
    93 K1500 burb (personal) 350 AT 3" Lift 250K+
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    Looking for a 1990's Miata for an engine swap

  5. #5
    murdog94's Avatar
    Join Date
    Feb 2008
    Cloquet, Minnesota, United States
    Blog Entries


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


    1997 Chevy S-10 Blazer 4X4 with 330K miles and counting (Hunting rig).

    2009 Saturn Aura XE (wifes car)

    2011 F-150 Crew 4X4

    "Hold it to the floor till you see God.... Then Brake!!!!"

  6. #6
    Jr. Mechanic
    Join Date
    Jan 2009
    Elizabeth City, NC


    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. #7
    Jr. Mechanic
    Join Date
    Jan 2009
    Elizabeth City, NC


    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. #8


    I just got done pulling the front cover off that GM 10-bolt front axle. Whew! Either that cover was never taken off since it was installed in 1982, or the cover was very well sealed. I had all the bolts out and was hammering a screwdriver in between the housing and the cover for probably 10 minutes before I got it to budge. Anyways, I checked the ring gear and found the axle is currently geared in 3.42. So, as I previously suspected, I'm going to have to get it re-geared up to 4.10s to match the rear.

    I've checked LMC, and it looks like they have all of the brackets I will need to hang the front axle under the truck. I've also determined roughly where the axle will hang, and it doesn't look terrible, though the front axle installation will definitely have to be done with the engine and transmission out so I can have space to work. Not a huge deal since I was planning to rebuild both while I was at it.

    Last weekened I sanded and painted the tow hooks I got from the junkyard. I'm painting them with a spray-on bedliner to give them texture. I think they're going to look great, though I stupidly painted them laying in the grass, and the grass got in the paint. So, it's back to lightly sanding them and giving them a couple more coats of paint. Hopefully I can have the hooks on the truck before the beggining of the next week.

    OK, that's all I have to report for now. Back to work!

  9. #9
    Legend mmorgan1865's Avatar
    Join Date
    Feb 2010
    Port Orange, Florida


    Good Luck Christopher. You obviously have the whole thing planned out well. Keep the pics coming.
    2010 Silverado Ext. Cab LTZ 2 WD 6 ft bed
    5.3L 6 speed w\ 3.08 rear end
    Navigation Package
    Westin lighted boards
    Undercover SE tonneau cover
    It's a start!

  10. #10
    Master Mechanic Big75's Avatar
    Join Date
    Nov 2009
    Seward, Nebraska, United States
    Blog Entries


    I know I'm jumping into this awfully late but why did you get a ten bolt front end? why not an HD 44 that already has 8 bolts? It will match up to the strength of that 14 bolt alot better. and what gear ratio will you go with?

    Once again, sorry I got into this late. I'm on brake at work and dont have time to read everything. forgot I said anything if this has already been discussed.
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