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Aussie RHD 1975 C20 2WD Resto mod

Discussion in 'Under Construction' started by pduffyd, Nov 11, 2019.

  1. pduffyd

    pduffyd Supporting Member Supporting Member

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    Truck Year:
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    Truck Model:
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    Engine Size:
    454
    [​IMG] Chev /Holden 1975 C20 resto, frame up.
    Hi all.
    This is my first ever thread, so please excuse if I make errors in my writing.
    This, as the title suggests will be about the resto of my recently purchased rolling chassis. Its a GMH complete knocked down (CKD) import 1975 Chevrolet C20. The base vehicle was a cab chassis with the stock 292 engine and SM465 /M20 4 speed gearbox. It has a GVW of 3720kg, so has the HD springs up front and the G51 leafs in the rear, with a 14 bolt FF axle running 4.10 gears.

    20190328_134635.jpg


    As you can see this is where I start.
    It did have the RHD cab but I sold it after removing all the ID tags.
    Eventually there will be a 59 Apache body on this frame.
    So this is where I start. I hope people will enjoy this and learn from my mistakes along the way!
     
    Last edited: Nov 12, 2019
  2. pduffyd

    pduffyd Supporting Member Supporting Member

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    First Name:
    Paul
    Truck Year:
    1975
    Truck Model:
    C20
    Engine Size:
    454
    Well I recently got to work on the frame, and I had to remove the structure that had been welded onto the top frame rails, that used to support an 11ft long flatbed!
    Lucky for me a 4.5in cutting wheels make short work of the welds, and metalwork.
    The front half of the flatbed frame was only bolted on so that was a relief.

    20190402_155357.jpg 20190402_155513.jpg 20190526_122920.jpg


    I removed the old fuel tank and cleaned up the rear frame area under.
    The welding hadnt done any damage to the frame.
     
    Last edited: Nov 12, 2019
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  3. animal

    animal Super Moderator Staff Member

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    Hi Paul :wave: looks like a cool project. Feel free to post your pics straight from your pc. The site gives you plenty of storage space and it avoids issues if the other host drops service. You just click the "upload a file" button next to post reply and choose the location you have your pics on your pc.
     
  4. pduffyd

    pduffyd Supporting Member Supporting Member

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    Thanks animal, I think i may have put this thread in the wrong place. Is it possible to move it to:

    2wd Pick-Ups C/R 20 2500 C/R 30 3500.

    Or is it ok where it is?
     
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  5. animal

    animal Super Moderator Staff Member

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    I think you're ok where you are at as it is very much "under construction". Of course they are all usually under construction....
     
  6. pduffyd

    pduffyd Supporting Member Supporting Member

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    The next part is, remove the rear end for cleaning inspection and repair as required.

    20190526_202301.jpg

    20190526_202346.jpg

    The rear shackles are very solid but the bushing were all seized so they had to be removed and serviced.


    20190526_202310.jpg

    The rebound bushes were also seized and the anti squeak or wear pads were done, so again these need to be replaced.

    20190526_202320.jpg

    These 8+1 leaf packs are in not bad shape but needed some TLC, so the rear was removed.
     
    Last edited: Nov 13, 2019
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  7. pduffyd

    pduffyd Supporting Member Supporting Member

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    Engine Size:
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    These 8+1 leaf packs are in not bad shape but needed some TLC, so the rear was removed.

    20190810_154702.jpg

    20190810_154730.jpg

    20190810_160809.jpg

    20190810_174944.jpg

    Well the good thing is rattle guns work well to loosen all those U bolts nuts, I used a fair bit of WD40 after a wire brush and let it soak for a while before I attempted the rattle gun. As you can see it all worked well. I had to use the 4.5 in cut off wheel on the shackle bolts but that was no big deal, just remember your safety gear, gloves goggles and shoes, my dads voice in my ears. I was glad of the shoes when I got a bit too close as the bolt cut and the front of the leaf just dropped and clipped my toe cap!!
    So now the rear end has been stripped, the cleaning can start.
    That's next time.
     
  8. 80BrownK10

    80BrownK10 Full Access Member

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    Nice thread. I'll be following along.
     
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  9. pduffyd

    pduffyd Supporting Member Supporting Member

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    Engine Size:
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    Thanks 80BrownK10, and everyone with their likes. :happy107:
     
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  10. pduffyd

    pduffyd Supporting Member Supporting Member

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    Truck Year:
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    Truck Model:
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    Engine Size:
    454
    After last time which was removing the rear end, it is cleaning and checking time.

    I moved the axle out of the way into the corner with the 454 V8 and the old M20/SM465 gearbox. The engine is being used but I am going to replace the box with a 4L80e, as this will be a highway truck the overdrive gear will put the rpm in the right range at 110kph approx 2100~2200, with the 4.10 rear end.

    20190810_160816.jpg

    excuse the other stuff around it, I was in the middle of making room.


    The job was to strip clean and inspect the spring packs one side at a time.
    After splitting the pack it was time to remove those worn out / seized bushings. I have seen plenty of videos on youtube about this, but drilling around the centre bushing rubber then smashing it with a hammer seemed a bit redundant as I have the springs out and apart.
    I used my small 6 ton press to push out the centre metal part of the bush, plenty of WD40 and a slightly smaller than the outside diameter of the bushing press piece. It came out quite easy.
    To get the rubber part of the bushing out, I stood the spring upright and supported it in a vice. I then used a reciprocating saw (sawzall) to just cut the rubber the length of the bush in two places about 90 degrees apart, to the depth of the outer metal part of the bushing. Then with a flat screw driver just flicked out the rubber.
    Now the outer metal part of the bushing. Where the eye of the leaf spring is bent around and formed to join itself to form the eye of one end of the spring, there is a slight gap between the bush and the spring eye. It is at this point where I used my die grinder to cut a small slot through the bushing material only along its length, being careful not to damage the spring. After this its easy to just tap out the outer bushing metal part leaving the spring eye ready to be cleaned. This whole process takes about 15 mins a bush. I would have shown some photos at this point but, yep, I forgot to take any! But I do have the springs apart, being cleaned and a reassembled pack.

    20190902_132116.jpg

    You can see what they were like before cleaning, pretty cruddy, during cleaning I used a grinder, lightly to get the worst of the rust off, and a 4.5in MAKO strip and clean cup wheel to clean up the whole spring.
    The springs were painted in POR15, but I left the middle bare (100mm approx 4.5in each side if the centre bolt) for proper clamping of the centre bolt, with a light smear of molybdenum grease to help stop the rust and wear. I painted the top of the first spring as its being clamped by the “u” bolt plate. The wear pads / anti squeak pads were all replaced as they were done. I used Skyjacker IN212C PTFE replacement pads, they are not exact as they are square not rectangular but the location pegs are correct and a slight trim on one end will have them fitting just fine. A darn sight better than the old worn out ones!

    One thing is I cant find the proper torque for the spring centre bolt, Ive got them at 25lb/ft right now. Anyone got the proper torque setting? I know the clamp pressure of the “u” bolts on the axle are going to hold everything a lot tighter, so maybe this is not that important, hence I cant find the damn torque spec!! lol.
     
  11. pduffyd

    pduffyd Supporting Member Supporting Member

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    Engine Size:
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    I have yet to clean the axel, I will do that next.
    This time around I am cleaning the rear half of the frame. I will basically use the same process as I did with the spring packs. Get them clean, as rust free as possible, then use the marine clean, and metal prep before applying the PRO15.
    As you can see I have made good headway so far in this.
    I couldnt resist doing one side in PRO15 before completing the rest of the prep work.

    20190927_105630.jpg 20190927_105634.jpg 20190927_105648.jpg

    Ok thats it for now. Im back to cleaning the rest on the rear chassis rails and painting in PRO15
     
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  12. pduffyd

    pduffyd Supporting Member Supporting Member

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    Truck Year:
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    Truck Model:
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    Engine Size:
    454
    I thought I would share the parts used for cleaning the old paint off the frame.
    I was originally going to paint strip it, but after doing a small bracket I realized this was going to cause a real mess.
    After a short search on the net I came across these items.

    20190929_150321.jpg

    Now I know this may cause loads of dust, my wife told me this as it found its way into the house, oopppps! But it was so much quicker and easier to strip the old paint and rust from the rails.
    Maybe when I do the front half I will use the big blue shed!

    The marine clean and metal prep. as shown.

    20190929_150545.jpg

    The metal prep is acidic, and leaves a zinc coating on the cleaned metal, Zinc phosphate? anyway, a simple process but it yield's good results.

    20190929_150446.jpg

    Just one word of warning the metal prep coats your driveway too, so maybe use it on a drop sheet or something.

    So here is the rear end of the frame painted and looking great, well, better than rust anyway!


    20190930_121523.jpg 20190930_121552.jpg

    That's it, now to re-assemble the rear end, right after I paint the axle!
     
  13. pduffyd

    pduffyd Supporting Member Supporting Member

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    Truck Model:
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    Engine Size:
    454
    So now the axle is done, I only did the diff housing and tubes. I will clean the brake back plates and the diff cover when I service the rear end later on.

    The replacement poly bushes for the springs just pushed in easily, but the centre did have to be pushed in with the aid on a soft hammer/mallet. These bushes were lubed with the grease that came with the kit. One thing I did do was, coat the attaching bolts with anti-seize grease so hopefully I wont need a cut off wheel if there is a next time to replace these bushings.
    See the photos for part numbers, there are 2x1.5 inch bushes ( rear of rear spring and shackle) and a 1.75 inch bush for the front, rear spring eye.

    20191001_145853.jpg 20191001_145937.jpg

    With the springs in place and torqued the axle was re installed, the new hardware used was all grade 8 and plated for long service life.
    Again all the U bolts were torqued to spec. Oh the centre spring bolt was cut down a bit and the threads peened over so the nut cant come loose.
    The spring rebound bolts were fed in from the inside to outside so that if they ever did come loose for some reason, they wont slice the inside of the tires.

    20191003_111854.jpg 20191003_111912.jpg 20191003_111919.jpg

    Well that about does it for the rear end, for now, I am going to install an sway bar and top shock mount reinforcement brackets.

    I will take a break for about a month now, before I start the front end. Cheers!
     
    Last edited: Nov 25, 2019
  14. pduffyd

    pduffyd Supporting Member Supporting Member

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    Finally got some time to have a go at the front end, yeah I couldn't wait a month.

    20191022_115215.jpg

    This is what we start with. Now before I got carried away I took a few photos of the shims on the top control arms for good measure. I put the alignment shims in separate bags for future use. Although I am replacing the control arms completely as there was not much difference in price between rebuilding these and buying new.

    20191022_115302.jpg 20191022_115319.jpg

    First remove the wheels, disk brake calipers, disk rotors, and backing plates, oh and shock absorbers.
    Now having done this on both sides I was ready to split the ball joints.

    I removed the tie rods first, with the idler arm and pitman arm as a complete assembly. It all has to be rebuilt anyway.

    Now I was expecting a real battle to separate the upper and lower ball joints, but after spraying the area with about 27 cans of WD40 (I may have exaggerated), and letting it soak overnight, it all came apart pretty easy using a 200mm pickle fork.

    I should say at this point, after removing the split pins, loosen off the ball joint nuts for the upper and lower joints, so the nut threads have at least half the nut still threaded on the joint. Then place a jack under the lower control arm you are about to separate, with about a 10mm clearance.
    This reason is quite clear once you separate the lower ball joint first, the suspension spring wants the whole control arm to catapult to the ground, the nut stops this of course, and the jack is a safety in case the nut strips its thread. Split the upper control arm joint, again a few good wacks on the pickle fork with a lump hammer did the job.
    Now bring the jack up to recompress the suspension spring and allow the nuts to become loose again on the ball joint shaft, remove the nuts and slowly release the jack pressure. Support the steering knuckle, this can be moved out of the way. The coil spring can now also be removed from the seat, of the lower control arm and the cross member.

    You can now unbolt the upper and lower control arms, ready in this case to be replaced, or refurbished as required.

    The lower control arms are held in place with two "U" bolts about 1 1/2" inside spacing by 1/2" thick. I believe that GM brought out a service bulletin about upping the U bolt from 1/2" to 9/16" because the 1/2" ones can snap? so 9/16th" ones are going back in. These are Dorman 13503, 1 kit for each side.

    20191030_103340.jpg 20191030_103414.jpg

    With the control arms and attached parts all removed as above it was a simple task to unbolt the engine mount brackets and engine cross member.
     
  15. pduffyd

    pduffyd Supporting Member Supporting Member

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    so time to de-grease the frame and removed parts.

    20191030_103327.jpg 20191030_103346.jpg 20191030_103459.jpg

    The other parts are on the shelf waiting for me to decide whether to replace them of keep them.
    I think I will keep the rotors as they seem new ish and are still 1.28" thick, no wear to be seen.

    20191030_103422.jpg

    again same as the rear end, its time to strip the frame and paint it again in POR15.
    That's next time!
     
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