Rear end swap? 89 4x4 3/4 ton to 71 K10

[franken]

Hey,
I've been trolling CL and ebay for a round pattern NP205 for quite a while and recently added NV4500 to the search. Up came an 89 Suburban 3/4 ton that the owner had converted to an NV4500/NP205 using an AA bellhousing.

I bought it since the price was less than the cost of a 205 and parts to make a clutch work would be more than the truck.

The not so original plan is snag all the bits off the Sub I want, part the rest and hopefully get the scrappers to drag the rest off and give me a few bucks.

Patient: 71 K10. Obviously 6 lug wheels
Doner: 89 4x4 3/4 ton w/ 14B SF rear. I think the front looked like a D44. Of course, 8 lug wheels.

Anyway, as I understand it, the front diff will bolt in, but the rear has wider spring pads.

Since the frames are similar widths, it must be the brackets on the frame that make the distance between the springs wider. Since I have the truck, I can grind or torch off the rivets and put the brackets, longer springs and finally the diff on the 71.

The deal also came with a 14B FF rear that I forgot about and hope to pick up tomorow. Not sure of the pad width on it, but it seems some had the same width as my 71.

I'd like the 3/4 ton suspension and heavier duty diffs.

Another option is putting the 71 body on the Suburban frame. Remember that Suburbans in 89 still had the 73-87 square body style. I've rolled around under both trucks and the body mounds seem fairly similar. Searches say the core support brackets need reworked, but that seems pretty doable. Wheelbases are different so it seems the rear diff would have to be moved regardless.

So the questions are (finally):

Should I just not bother with the diff swap and stick with the half ton stuff? Since a truck w/o axles won't roll this would be easiest for the scrappers. Any chance HF castors will support the frame and shell of a square sub long enough to drag it on a rollback?

Should I get the spring pads moved on the 14B SF, or use the brackets from the 89, drill new holes, and bolt them on (since I obviously can't do rivets like the factory)?

Or, should I swap bodies?

I have tools, air toys, air system, and the compressor to run it, OA torch, cherry picker, etc. so all I lack is ambition...

Sorry for the long and rambling first post... I'm pretty thick skinned so yell at me if needed. I did search and have spent hours reading up on the subject.

Advice?

[obijuan]

Put the 89 burb rear springs and 14 bolt full floater in. Cut and weld new perches. Imo, easiest and best way out.
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Why the round 205? Why not the 32 spline 241 that came in the 89?

[Mike C]

If you do the 'burb rear springs you have to move the shackle mount back 4" as they are 56" eye-to-eye and not 52" like the stock ones.

I have '86 3/4 ton sub running gear under my Jimmy. Just re-weld perches and shock mounts. I re-used my 12 bolt parking brake cables on the semi-float 14.

1/2 and 3/4 ton square bodies have 42.5" spring centers while one tons have 40.5" spring centers which is the same as 67-72 4x4 trucks.

[franken]

I measured some things and realize the later springs are longer. I'm thinking this isn't sucha bad thing even though the hangers will need to be removed and those from the 89 put in different spots.

I picked up the 14 bolt FF last weekend, but no drums, backing plates, or brake hardware. Just the diff, axles and hubs. The front rotor and caliper swap looks clean, but no parking brake sounds iffy, and the El Dorado calipers have a bad reputation.

I'll look into the spring perch move cost as well...

Thanks!

[obijuan]

Longer springs tend to ride better. Ive got 56s with a shackle flip on my blazer and it really does ride good.
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[franken]

That's what I thought. Also I think the wider perches would help stability somewhat. GM make the change for a reason I would think...

[Mr. 250r]

If your gonna move perches i wouldn't bother saving them i would get these http://www.ballisticfabrication.com/...ch_p_1485.html i have them good stuff you can move axle forward or backward if needed or keep in stock location although i did have to drill out the center hole a little bigger for my lift block

[franken]

I wasn't planning to attempt to save the perches, but cut them off and have new put in the proper location. It's just easier to say move than that last...

If my measurements and guesses are right, the 14BFF I have will be 3.5" wider on each side than mt K10 rear. Even though the front is wider than the back I doubt its that much wider. More measuring in store...

Pulled a few parts off the Sub yesterday and pulled the diff I picked up last weekend out of the back. It wasn't fun moving that thing, but I got to play with air toys and love my compressor system...

I'm not liking the no parking brake, or Eldo caliper options for a rear disk. I also trolled the scrap yards measuring perches and WMS-WMS. It seems both get wider and wider as the trucks get newer.

[Mike C]

try and save the perches. The axle housing is larger OD than the commonly available perches but that's your call.

I ran 3 5/8 bs on my 6 lug wheels 10" Centerlines and 4 1/2" on my 9.75" wide 8 lug wheels. That keeps the rear at about the same overall width.

[franken]

I see that the perches are castings, so I guess it might be wise to try to save them.

I was looking at the 14 bolt bible page on pirate and see that the cab and chassis hubs can be used to change the WMS-WMS. It looks like about 2" per side.

I wonder if the hubs from older rears can be used on a 200-2010 FF diff. More digging...

I put the truck up on CL for parts. It only took a few hours for someone to be all over the NV4500 trans and AA BH... Looks like I'll have $200 in the round pattern 205, hydraulic clutch setup, 3 diffs and the engine. Of course, I have to pull the trans and TC.

[franken]

After much scrapyard trolling, I've found a 7x C30 with a 14B diff that looks like it'll bolt in. Yay.

The trans and AA BH from the parts truck are pending sale for almost what I have in the truck so the deal looks as good as hoped. My labor at 100* temps is unpaid

Still have to get the non-rolling carcass out of my driveway. Not sure the city will like it sitting there. The "I'll take you're scrap car" people are startlingly choosy...

[franken]

Sold the trans today. Crazy guy offered me more than I quoted him.
He still got a great deal.
I found that the bellhousing works w/ my trans so I didn't sell it. That saves around $400 so this deal is working out well...