3/4 to 1/2 ton suspension

[GMC 3]

on our year trucks,is the front crossmember that the lower a-arms bolt to identical between 1/2 and 3/4 ton? I know the lower a-arms are different, but Are the upper a-arms interchangeable? If so, Are the upper ball joints the same for 73-up between 1/2 and 3/4 ton Thank you

[69 longhorn]

I did that swap on my longhorn.....upper a arms will work,you need 71-72 1/2 ton lower a arms(to retain the old style bushings).then use the ball joints & outer tierod for the year of the 1/2 ton spindle spindle.If you are converting a 71-72,you should be ok on the rest of the steer link pcs......if 70 or older,you may have to change the center link & complete tie rod assys. 3/4 & 1/2 ton ball joints & tie rods ARE different,as is the size of the hole in the lower balljoint.I still have the original cross member in my longhorn. good luck ...69 longhorn.

[This message has been edited by 69 longhorn (edited March 20, 2002).]

[Fast68Chevy]

theres been a great debate over the hole in the lower arms being larger on 3/4 ton arms than on 1/2 ton arms, chris(cant remember user name) says lower arms holes are same size on both so ... I had a pair of 3/4 ton lower arms i could have measure that on, but theyre gone now, but i have a 3/4 ton complete front end i could maybe check that on. i owuld think the holes are larger, but who knows now..

the crossmemeber engine cradles are all same and all the arms will swap all around, 64-87

3/4 and 1 ton arms are all solid pack bushings just like on 67-72 1/2 ton arms,

73-up 1/2 ton arms use rubber bushings and studs unlike all 67-72 and 73-up 3/4 and 1 ton arms, but will all stil bolt onto whichever cradle

there are different diameters(diameter of the bolt itself) of lower arm U bolts however
good luck

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[69 longhorn]

I can clue you on that hole size.....& I dont have to measure! I swapped em,& im telling you that the 1/2 ton ball joint DONT fit the 3/4 ton arm..... the hole is too big........69 longhorn.

[Mike C]

As noted the ball joints are different, they are talking about the alignment hole on the cradle where the a-arm crossshaft bolts to the frame as far as I can tell.

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70 GMC 3/4 ton Sierra Grande 402/TH400
72 Jimmy 4WD 4spd 4" & 35's
64 Corvette Coupe
68 Camaro 'vert TPI & TH700
69 Z/28 355 12.6's @110
72 Datsun 240Z-ol' reliable

[67Blacksheep]

GMC-3,
I was glad to see your question. I am preparing to perform the swap in the next week or two. I followed the advice from a fellow from DC truck, who suggested that I obtain an entire front section including the member. Supposedly the conversion consists of about 11 bolts, and the engine can stay in the vehicle the whole time. When completed, every component will match, and will be provided by the donor vehicle. I will let you know how well it works if I don't kill myself in the process!!

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[69 longhorn]

Pin on the cradle/alignment hole on the cross shaft? I cant say,I used the 3/4 ton shafts & screws on the 1/2 ton arms......

[jostrans68]

just finishing my 68 disc conversion using 72 parts the arms were the same with 1 exception. the steering stops are different. can be fixed though............

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68 c20 in progress 327 TH400 tach dash Disc Brakes and soon 3.90 rear gears.. have many new parts now just need the time..... Sound Familar