1989 Suburban 2WD 3/4 to 1/2 Swap?

[Crank]

Hey folks, I live in Kentucky where the rust is plentiful, but a year or so ago, I picked up a very solid 89 Suburban 2wd, 454/th400 3/4 ton, for what I think was a good price of $600, not running. Luckily for me, a new $28 starter solenoid and a cheap Walmart battery and she fired up.

Plans for this truck have always been to stuff it on the ground, and make it a family friendly hot rod(I have 4 kiddos, 6 and under.) So I purchased a rolling chassis of another 89 suburban 2wd, but this time 1/2 ton. Simply stripped off all the 1/2 components and crushed the rest. Here is where I'm hoping for some help...

I removed the springs/rear axle, and front crossmember and all suspension up front. BUTTTT, is the 3/4 and 1/2 crossmember the same. I feel like I pretty much need to pull the motor if I want to swap the crossmember, or if the control arm bolt sizes and everything else as far as connecting hardware goes, I'll just refurbish the existing 1/2 ton control arms, throw drop spindles on it, and a flip kit and I'll be where I want to be.

[1976gmc20]

Seems like a damn shame to me

Great old 'Burban, you could pull a house trailer with it.

[Crank]

Originally Posted by 1976gmc20

Seems like a damn shame to me

Really not looking to pull a house trailer with an old crusty Suburban, but what I would like to do is cruise to get some ice cream or take in a car show with my pile of kids, the big block is staying as is the TH400, so should still be able to pull a moderate load of whatever I need. I do have a diesel Excursion for pulling things though, after getting rid of the Cummins pictured.

Hopefully someone will know whether I'll need to swap to the 1/2 ton crossmember or can utilize the 3/4 that is currently installed so I wont have to yank the motor.

[lolife99]

I would just swap everything from the a-arms out and leave the original crossmember in place.
Also use all the 1/2-ton steering.

[TwoFiftyShifter]

You should be tarred and feathered for even considering a swap on that suburban. They only made 850 thousand of those!!!!

[SCOTI]

Originally Posted by lolife99

I would just swap everything from the a-arms out and leave the original crossmember in place.
Also use all the 1/2-ton steering.

The upper a-arm studs are likely larger on the 3/4 ton so the shafts might need to be drilled out to utilize the 1/2 ton arms as is.

The x-member is definitely interchangeable. I have a crossmember from a 1/2 ton under my 1-ton dually.

[Crank]

Originally Posted by SCOTI

The upper a-arm studs are likely larger on the 3/4 ton so the shafts might need to be drilled out to utilize the 1/2 ton arms as is.

The x-member is definitely interchangeable. I have a crossmember from a 1/2 ton under my 1-ton dually.

I guess I know that the entire crossmember will bolt in it, but that’ll just about require me to pull the motor. My question I guess is, are the crossmembers identical? If so no harm in leaving it there, but if there is something drilled larger for 3/4 arms, but then would make the holes oversized for 1/2 ton components I’ll swap the whole assembly.
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[SCOTI]

Originally Posted by Crank

I guess I know that the entire crossmember will bolt in it, but that’ll just about require me to pull the motor. My question I guess is, are the crossmembers identical? If so no harm in leaving it there, but if there is something drilled larger for 3/4 arms, but then would make the holes oversized for 1/2 ton components I’ll swap the whole assembly.
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Identical? IDK for sure. There may be a hole or 2 that aren't the same. Beyond that, they're similar enough that the parts will swap over & no reason to swap x-members unless the 'new' unit is freshly painted/detailed.

[lolife99]

Originally Posted by SCOTI

The upper a-arm studs are likely larger on the 3/4 ton so the shafts might need to be drilled out to utilize the 1/2 ton arms as is.
.

The other option would be to put a 1/2-ton ballpoint in the 3/4-ton UPPER a-arm.
You can’t do that with the lower a-arm because the 3/4-ton ballpoint hole is larger than the 1/2-ton version.

I would still not swap the crossmember itself.

[SCOTI]

Originally Posted by lolife99

The other option would be to put a 1/2-ton ballpoint in the 3/4-ton UPPER a-arm.
You can’t do that with the lower a-arm because the 3/4-ton ballpoint hole is larger than the 1/2-ton version.

I would still not swap the crossmember itself.

Yep.

[mr48chev]

Since you already have the 1/2 ton crossmember unbolted you should be able to unbolt the engine from the mounts, and lift it up and if needed make a bar that holds it up that sets across the lips of the fenders much the same way one does when you hold a transverse engine up to swap transmissions. Then drop the crossmember out and raise the 1/2 ton unit back up in place and bolt it in all cleaned, painted and ready to go.

Remember that if you swap A arms, spindles and springs you have to:
Take the spindles off.
unbolt the UPPer A arms.
Remove the springs
unbolt the lower A arms.

^^^^ Twice

Bolt the 1/2 lower A arms to the Crossmember
Bolt the upper A arms on
fight the springs back into place (easy for me, hard for some guys)
bolt the spindles back on,

A quick check of the upper control arm bolts will tell the story there.

You may want to replace all the bushings and ball joints in the 1/2 suspension and that makes the bolt and unbolt a moot point.

No photos but 20 years ago my son and I swapped front subframes under my wife's 76 Cad Seville by jacking the car up pretty high and blocking it up , using my gantry and chain hoist to hold the engine up. dropping the bent subframe out, sliding the good one in and raising it up and bolting it back together. It wasn't easy but we had it done in a weekend and my wife drove it to work on Monday.

[Crank]

Originally Posted by mr48chev

Remember that if you swap A arms, spindles and springs you have to:
Take the spindles off.
unbolt the UPPer A arms.
Remove the springs
unbolt the lower A arms.

^^^^ Twice
A quick check of the upper control arm bolts will tell the story there.

You may want to replace all the bushings and ball joints in the 1/2 suspension and that makes the bolt and unbolt a moot point.

I am planning on doing drop springs and spindles while I do it, and swapping in new Moog upper control arms and rebuilding the steering linkage while I do it, so it’ll al be fresh. Just really need to rebuild the lower control arms as I can’t find replacements.

I should just bite the bullet and yank the motor, it’s a slimy bastard and could stand to get some leaks fixed but it’s just me and I don’t want to yank it all apart and never get it back together. I’d like to just get it riding right and play with the motor another time. I might do like you said tho, just lift the motor and swap the crossmember. Heck who knows
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