Starting a Suburban build.....

[John90XJ]

So I've recently inherited an '89 Suburban. It's a 1/2 ton, 350, 700R4, NP241, 10 bolts, very nice shape with 287k miles and a rebuilt trans....otherwise very stock. It's got all the power options including rear air. It's nice to drive as it is and gets pretty respectable mileage. I do have every maintenance record for the last 16 years so I'm fairly confident it's OK.

I have a Jeep XJ that I use for the Rubicon, Moab and places like that and would be keeping the Suburban on the road and modest off-road areas. I would like to tow with it on a rare occasion and otherwise use it for a camping/pseudo pickup. I live in Washington and would likely use it around here as well as taking it to Baja and points south of where I live.

I'm convinced that replacing the axles is a good idea for a gear ratio change more than anything else. While I'm going to try and tow the Jeep with it once or twice a year, I'm not convinced I need to go beyond a 12 bolt rear axle. I'm trying to balance the additional weight of a 14 bolt rear end against the rare need for its strength.

As for performance mods, I'm not sure where to even start or if the need exists. It's a bone stock TBI setup now with single exhaust.

For the first time I have a rig that needs bigger tires purely for aesthetics and I would like to run 32s or 33s without lifting much (or at all) and getting the most of the gear ratio change. I'm leaning toward 32s which would work well with 4.10s. If I found 4.56 axles I would likely run 33s. I'm partial to BFG AT/KOs.

I'm also thinking about keeping the outside as "clean" as possible so I wouldn't want to add racks, RTTs, or other things that create drag. Other than that, I'm fairly open to suggestions and figuring out what direction to take this thing.

Any suggestions on axles, performance mods, weaknesses, build ideas, anything at all.....this is an open book other than the basic ideas shown above.

What do you guys think?

 

[ujoint]

If you're going to take the time to swap out the rear axle, go ahead & put a 14 bolt 10.5" axle in it. They're so cheap & bulletproof. And if you're only running 33's or 35's, an 8 lug Dana 44 will be fine, but I'd throw in a 60.

 

[ntsqd]

I have a '91 1500. I used to own a '79 3/4t so the 8 lug front conversion stuff was available. That is an exceptionally simple swap - about as involved as re-packing wheel bearings. I went to the 14bff for a couple of reasons, I know I can't hurt it as long as it has oil in it, and I got a killer deal on one with the right ratio, a Detroit, and all new bearings. Yes, the unsprung weight is not pleasant to contemplate, however with a set of non remote Res Bils 7100's on the rear I don't really notice much change in ride quality. Perhaps I might had I driven the exact combo, less the 14, for any distance but I did not. I rate the piece of mind over not having C-Clip axles and their attendant funky wheel bearings fairly high. A flanged axle's design is poor enough w/o also hardening the shaft right at the stress riser so that the bearing's rollers can roll directly on the shaft.
Plus, the larger brakes are a real bonus, towing or not.

I've had mine up to Barcroft Research Station (12,500ft) in CA's White Mtns. The hills are just as steep, but the truck ran fine all the way to the top. In fact I notice that it like the 3500-9000 ft range the best. Tells me I may have a lean condition here at sea level. The only engine mod it has is the addition of tall air filter can lid & filter element off the '79

The 1/2t's have a less deep radiator by about 3/8" The core support accepts either and the lower rubber mounts can be modified by razor blade to do so too. The upper rubber parts are different as are the clamps that hold them. The longer clamp pieces aren't available from my dealer any more, but lengthening them wouldn't be too difficult a cut-n-fab job. The longer upper rubber pieces are still available as of this posting.

If the 89's have the older one piece radiator clamp you'll need to address that. They are famous for letting the radiator bounce out on Baja's washboard roads. Ideal would be a turnbuckle arrangement btwn the top & bottom mounts. Not much space for that. Have seen all-thread used to tie the upper to the fender liners low below the battery trays & next to the frame rails. Can't tie direct to the rails due to bridging the body mount.

700's don't want a lot heat in them. BowTie Overdrives says they want to see 160*f max in the pan (where they recommend putting the sender). I've yet to achieve that, occasionally by a large margin. knocks on wood.....

If you can search over on cK5, search this user name. I posted a Rancho p/n for a 2" front spring that is NOT in their regular listing. It is in their numeric listing and it is intended to be a "Pre-Runner" spring for a K5. It works very nicely in a SBC powered Sub (I've had them under both). Yields about 2" of lift and rides much, much, much better than stock.

 

[robert j. yates]

I have an 86 2500 4x4 (picture attached) that I rescued from the crusher (theft recovery) and slowly rebuilt. Its been a fine truck and for awhile, I even used it to camp out at the dry lakebed at Johnson Valley when I was heavily into rock crawling. Plenty of room for a queen sized air mattress in back with the seats down. The rear AC also rocks but that took me a bit of work to get it working correctly. Same with the rear window.

The original 454 was long gone when I got the truck (or what was left of it)and I have a mild 350 in it now. Basically to the reman 350 I added a RV cam, Edelbrock intake and carb and a set of Thorley ceramic coated headers. That 350 had no problem towing my Jeep (on a 18' all metal car hauler) to Moab and back along with a trip to the Rubicon so I wouldn't worry about your 350 not being up to the task. Edelbrock does make a TBI upgrade for your motor that is smog legal if you do want to look for more power and a set of good headers never hurts.

If you do plan to tow your Jeep then I would go for the 14bolt. There are actually 2 14 bolts...mine was the small 14 but I've never had a problem with it. My truck is actually 8 lug front and rear which I think is a good strength upgrade so don't shy away from the 10bolt up front or the small 14.

I can comment on your t-case and tranny as I have a 208 and a TH400.

As for suspension.... I am running a set of 1 ton spec Deaver soft rides with airbags in the rear along with a set of Rancho 2" lift springs up front. I have RS5000's all the way around. It rides pretty crappy unloaded but I set it up to tow my TJ and when thats connected to the Burb...it rides like a caddy. I'm running 265/75/16 BFG AT's on it and am on my second set. I have managed about 35K out of each set so I am happy with the tire in that application. FYI....this tire fits but barely in the spare compartment behind the wheel well.

A couple of things that have given me on-going problems are the rear window...I'm on window motor number 2 for that. The rear ac...I am on blower motor number 2 for that as well. The power windows just suck period and the 20+ years old weather stripping is failing. Front ball joints and front hubs. Last time around I switched to a set of Warn Premium hubs and have not had a problem since. I have also had bracket problems for the AC and alternator but part of that was my doing in order to accomodate the header on the drivers side. My truck also has a habit of toasting HEI modules so I keep a few spares in the glove box.

The positive to crappy gas milage is that these trucks can haul alot of stuff, tow a pretty good load and are cheap to buy and maintain. The junk yards are full of these trucks and you don't necessarily need to get Burb parts for under the hood.

Good luck with your build.

 

[Grim Reaper]

I think 89 10 bolt may be as strong as a 12 bolt. the last couple years of the box bodies the 10 bolts got a little strong shafts.

Honestly if you plan to load this girl down or tow that Xj then get at least the Semifloater 14. They can be had with 6 lug and depending on how your truck was optioned there is a possiblitly it has it.

Full floater 14's can be had for $100-150 if you watch for them The only difference between the 3/4 ton front 10 and the the half ton is the hub and backing plate. Waxer did a nice write up on converting over at CK5 in the tech section.

I knew I woud be towing a camper and I had planned to tow my trail rig so I wasn't about to buy anything with out a 14. At this time m only regret is gettign the 454 2wd and not getting a 350 4wd. The 454 is brutal on fuel.

Here is my 88 with 87,000 original miles.

 

[Grim Reaper]

I have an 86 2500 4x4 (picture attached) that I rescued from the crusher (theft recovery) and slowly rebuilt.
The original 454 was long gone when I got the truck (or what was left of it)and I have a mild 350 in it now. Basically to the reman 350 I added a RV cam, Edelbrock intake and carb and a set of Thorley ceramic coated headers. That 350 had no problem towing my Jeep (on a 18' all metal car hauler) to Moab and back along with a trip to the Rubicon so I wouldn't worry about your 350 not being up to the task. Edelbrock does make a TBI upgrade for your motor that is smog legal if you do want to look for more power and a set of good headers never hurts.

Truck didn't come with a 454 from the factory. Check the RPO codes on the sticker in the glove box or run the vin and it will show a 350. GM would not put the 454 in a 3/4 4x4 because they knew the engine would destroy the front axle and the D60 was never available in a Burb.

Here is the sales brochure and its hard to read but no 454 is listed for a K20 anything.
http://brochures.slosh.com/index.shtml?1986

Here is how to read the VIN
http://www.lmctruck.com/icatalog/csb/0009.asp


8th digit would have to be a N or a W to have come with a 454.
K is 350
If you find it is a 454 I want to see a picture of the VIN and RPO codes. I been playing this game for years and so far nobody can prove me wrong and provide a image of a 4wd 454 burb made before 92.

 

[ntsqd]

Had to come home to get pics of mine.

Yes, the mascot is a rubber duck.
Yes, there are rear shocks. Just not in the stock axle hangers that hadn't yet been cut off.

 

[robert j. yates]

Uh....OK. I said it was a theft recovery so I have a salvage title and VIN. I was merely repeating what I was told when I bought the truck. If you can tell me where I might find the actal VIN, I'll be glad to post it for you and you can have at it.

As for whether it ever had a 454....I don't really care as evidenced by my choice to put a 350 in the truck.

Truck didn't come with a 454 from the factory. Check the RPO codes on the sticker in the glove box or run the vin and it will show a 350. GM would not put the 454 in a 3/4 4x4 because they knew the engine would destroy the front axle and the D60 was never available in a Burb.

Here is the sales brochure and its hard to read but no 454 is listed for a K20 anything.
http://brochures.slosh.com/index.shtml?1986

Here is how to read the VIN
http://www.lmctruck.com/icatalog/csb/0009.asp


8th digit would have to be a N or a W to have come with a 454.
K is 350
If you find it is a 454 I want to see a picture of the VIN and RPO codes. I been playing this game for years and so far nobody can prove me wrong and provide a image of a 4wd 454 burb made before 92.

 

[Grim Reaper]

Uh....OK. I said it was a theft recovery so I have a salvage title and VIN. I was merely repeating what I was told when I bought the truck. If you can tell me where I might find the actal VIN, I'll be glad to post it for you and you can have at it.

As for whether it ever had a 454....I don't really care as evidenced by my choice to put a 350 in the truck.

Somebody went to the trouble to remove the windsheild to replace the VIN?

I would think the first part of the vin would stay the same as it carries the info needed for smogging. The Driver door has a sticker that should have the vin if it is still there. The RPO sticker in the glove box should also have it.

 

[John90XJ]

Thanks guys....this is giving me a lot to think about.

Are there any steering changes that would come from changing to to 8 lug axles or is that all the same?

Driveshaft lengths front or rear going to be the same? U-joint size?

Any weird things to look for in doing the axle swap?

 

[ntsqd]

Steering remains the same. HAve a look at the article Grim mentioned, the 8 lug front swap really is simple.

No idea on DS stuff, I used pre-existing parts from the '79

Look over the p-brake cable configuration. My rear axle's system is not compatible with the 91's pull cable. There appears to be 2 different designs. I'll venture an early and a late model. You'll want the donor axle to match or you'll spend a lot of time and money trying to get a functioning p-brake.

One way I plan to dump some of the 14bff's massive unsprung weight is to go to rear discs, so the mis-match wasn't a big deal to me.

 

[John90XJ]

You'll want the donor axle to match or you'll spend a lot of time and money trying to get a functioning p-brake.

One way I plan to dump some of the 14bff's massive unsprung weight is to go to rear discs, so the mis-match wasn't a big deal to me.

Are you saying that the 14 b with a disc conversion uses the caliper for the parking brake instead of a "drum in hat" style like on Ford 8.8s (which is what I have on the Jeep)?

I would be inclined to go with rear discs for their simplicity and that would make it that much easier.

 

[ntsqd]

You could do it using Cad hydro-mechanical calipers with any 14b. I won't and don't suggest it.

What I just posted on a list:

Hydro-Mechanical calipers are not a good design idea. The adjuster mechanism ends up in the mildly corrosive fluid (brake fluid is hygroscopic afterall) and will sieze. Not if, when.

The other problem with a p-brake caliper is getting enough leverage without resulting in too much cable pull. This was a constant design challenge we fought when I was at wilwood working on OE application stuff. Note that their street rod p-brake systems use either the Exploder p-brake mechanism or the very similar Corvette parts.

Also note that those Europeon cars we have come to expect engineering excellence from have never used a hydro-mechanical caliper. Their p-brakes have always been a drum system inside the rotor hat. This despite the known tendency for drums to freeze up in their cold host countries, like Germany and Sweden.

For pure position holding power a drum brake can't be beat. P-type drum brakes are not of the self-energizing design type, not in the classic Bendix self-energizing design type anyway.

I plan to do an SYE and go to a DS p-brake of some sort. Now if I just hadn't thrown away that p-brake off the SM420........

In the real late model 14bff's there is a drum-in-hat type p-brake rear disc system. Those don't last long when they do show up.
I've no experience with the 14bsf axles, no idea what they might have available.

 

[John90XJ]

Interesting. You learn something everyday.

Thanks.

 

[ujoint]

The steering arm will be different on the 60, but your drag link should bolt up. The driveshafts will have to be shortened for the bigger axles, unless you're throwing a lift on at the same time.