1/2 to 3/4 2 wd conversion

[qksilver]

Unexpectedly was able to sell a project, so starting work on the next one. Been out of the trucks for a while because of being burnt out. Bought way too many trucks, projects and parts, then piled them all in my shop. Can't get to much with out moving way too much stuff.

The easiest thing to put together is one of my 72 1/2 2 wheel drive burbs. I need to replace my 99 3/4 burb because it's going on 225,000 miles and I don't have the money to rebuild what it needs.

Here is what I have that is easy to get to. Complete rebuilt 3/4 disc brake front suspension, bought from a member out of New Jersey, a 68 292 engine 3/4 rear, a no idea year 14 bolt rear and a buried 72 GMC 3/4 leaf spring BB engine auto rear bought from Billsbowtie.

I want to have as close to 3:55 ratio rear under my burb. Will use a turbo 400 trans with a 454 so I have torque but want some gas mileage.

The 68 3/4 will bolt in, I have 3/4 trailing arms etc but think the ratio is high because of the 292. i counted the turns of the yoke after turning the drum one time, the pinion turned 3 and a half or so turns. The rear is the type that has a rear cover and a bolt in hogs head. No options on the spid and the original rear, 292 3 speed on tree.

14 bolt no idea on ratio but thinking 3:73........problem no panard bar mount and spring perches too wide but new drums and brakes.

rear out of 72 GMC BB auto, buried behind major stuff, stock rear, no idea of ratio and it's a leaf spring rear.

I like the 14 bolt but have looked at swap kits and they look fine for 1/2 but rather spindly for a 3/4.

I have all the spring perches (frame mounts),springs and crossmembers from the GMC. I have all the spring perches( frame mounts) and springs from the PO attempt to swap on to a 72 LW 3/4 frame that had trailing arms. Would still have the problem of the perches to wide and the PO use of 1/2 aftermarket flimsy spring pads.

I thought about doing a leaf spring conversion but trying to mount all of that, crossmembers, perches and reinforcement brackets would mean a lot of drilling with no work space unless I lifted the body off of the frame. This I can't/won't do for many reasons.

So after all of this info, what advise, recommendations or.........What would you guys do. A 1/2 burb is iffy towing wise. A 3/4 burb would fit my needs like my 99 burb did.

Thanks to all...............
Steve

[capev86]

isn't the late model burb 14 bolt the semi-floater? the full floater is the way to go, especially a 2000+ axle with wider track and disc brakes. pretty easy to add trailing arm perches and a track bar mount. the coil spring setup at all 4 corners is the more attractive way to go and it rides nice too.

a 3.50-3.70 ratio is a good setup for towing especially with a big block in front of it, but i would skip the stone age t400 and get a 4l80. even a 200 or 700 overdrive can be built to take over 500hp/tq. it just makes sense in the modern day with fuel prices and environmental responsibility. believe me, my 72 burb w/ 4.57 rear could pull stumps nobodies business, but a lot is left to be desired in long distance highway driving. hoping with my 4.10 swap (just done at the shop today) i will at least be able to do 50-60. the overdrive is in the future (borg warner unit on the sagniaw 3OT).

as for needing a 3/4 ton truck.....it depends on what you will be doing with it. the 1/2 ton burb is a good tow vehicle too provided you have it set up right. the standard 3/4 ton (2000 lb per side) rear coil springs were optional on the 1/2 ton and on a burb they are worth their weight in gold. the stock 1400 lb rated units don't leave any capacity for trailer tongue weight.

the other mods i would recommend on any truck are a sway bar and rear poly bushings. i have CPP sway bars and trailing arm and track bar bushings on my 72 burb 3/4 ton because i want maximum stability for trailer towing and spirited solo driving. the track bar on the 3/4 ton is bigger but CPP carries the bigger bushings for it. as for an inexpensive factory style sway bar upgrade, get the stock one off an 70's-80's 1 ton or 3/4 ton camper special. it should measure 1-1/4" diameter which is far bigger than the stock unit that was optional on our vintage burbs. even my dad's 84 and 87 2wd burbs only had a 1-1/8. a rear sway bar is a good idea too, but the stiffer rear coils and big front sway bar will make for a very predictable ride. the sway bar is a bolt in job.

my dad pulled the family's 6,000 pound '71 holiday with his 72 burb.....1/2 ton 2wd, '77 305 w/ rv cam and q-jet, t350, 3.73 rear, factory sway bar, 3/4 ton rear coil springs, etc. i do like my 3/4 ton but i wouldn't hesitate to use a 1/2 ton for most jobs.

[qksilver]

I appreciate the comments. I want to use as many parts as i have. I like having a margin of safety that a 3/4 brings, both in pulling and more importantly stopping. Using a 400 trans is also part of that margin, a 700 can be built to take a good amount of power but generally not in a heavy vehicle and I have a rebuilt 400 already. The 480le would be a perfect choice as it has been in my 99 burb.

190,000 on the original trans, fluid changed every 20,000 and the factory tow package with a trans cooler. Half of the mileage has come from towing loads from all over the USA atleast 8000 pounds usually more.

Money is really tight and this is a hobby. So what ever I need will only come from what I already have or from selling some of the stock pile. I have way to much money already invested and will put no more in. Time I have!

Thanks,
Steve

[raycow]

Originally Posted by qksilver

So after all of this info, what advise, recommendations or.........What would you guys do.

Going from your description, your 68 rear is an H052, which never came with anything taller than 4.10. The 72 3/4 ton rear could be about as bad, although being a GMC, it might have a Dana 60, so it would be worth counting the ratio on that one. When you do this, you want to hold one wheel from turning while you turn the other wheel TWO revolutions. I think your best bet is going to be the 14 bolt, because the later trucks usually had taller gearing. Be sure to count the ratio on that one too.

IMO, a leaf spring swap would be too much trouble to even think about. You can get aftermarket weld-on brackets for the trailing arms and panhard bar. If your time is a lot cheaper than your money, you can even cut the brackets off the 68 rear and weld them onto the 14 bolt. The 3/4 ton trailing arms will bolt to your 1/2 ton frame.

If your 3/4 ton front end is no newer than 87 it should bolt on to your frame, needing only a couple of new holes to be drilled.


Ray