Author Topic: K20 4" lift- Shock issues  (Read 1697 times)

Offline 81vee

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K20 4" lift- Shock issues
« on: April 11, 2018, 11:25:09 AM »
G'day guys,

Working on a mid 70's K20 with fully floating rear and of course a solid axle on the front  :)

The previous owner of this truck seemed to mickey mouse just about everything. I recently lifted both the front and rear for medium-term storage, and noticed that the height of the front axle basically didn't change, and the rear barely did anything either. I also noticed that the shocks seem to be fully extended, with the length of the piston coming out matching the casing length, even when on the ground. I'm not a suspension king or anything, but something doesn't seem right. Maybe it's me. FYI, the truck was received with the lift installed. About how much travel should I get for both the front and rear with this setup? I want this thing to be safe. I don't feel like rolling over, and it doesn't help that it has short 33'' tires and stiff suspension.

Let me know what you think.

-81vee
1981 C10 w/ '74-'78 K20 frame 350 crate 4.10 rear SM465 4" lift
'05 Colorado LS Z71 crew cab victory red

Online ehjorten

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Re: K20 4" lift- Shock issues
« Reply #1 on: April 11, 2018, 01:51:11 PM »
what do you mean lifted the front and rear for medium-term storage?  Do you mean that you jacked the axles and tires off of the ground?  If so...your suspension shouldn't move much!  You are just raising the vehicle off of the ground.
-Erik-
1991 V3500 - Gen V TBI 454, 4L80E, NP205, 14 bolt FF, D60, 8" Lift on 35s
1977 K20 Silverado - 350, THM350, NP203, 14 bolt FF, D44, Stock Lift on 31s
1969 Chevelle Malibu Sport Coupe - EFI350, THM350
1968 Chevrolet Step-side Pickup - 300HP L6

Offline 81vee

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Re: K20 4" lift- Shock issues
« Reply #2 on: April 11, 2018, 04:20:26 PM »
Yes, thats what I did with each axle separately, but shouldn't there be a few inches of separation between full weight on the ground vs axle in the air? You know, so that when you go over a pot hole, instead of having your truck sink into the ground, your shock and tire move instead. I know that this truck has solid axles, but in my opinion, they should at least have a little shock absorbing potential. Whenever I lift anything else, you get at least two inches between raising the frame and raising the tires off the ground.

-81vee
1981 C10 w/ '74-'78 K20 frame 350 crate 4.10 rear SM465 4" lift
'05 Colorado LS Z71 crew cab victory red

Offline blazer74

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Re: K20 4" lift- Shock issues
« Reply #3 on: April 11, 2018, 07:15:25 PM »
Support the axles, Disconnect one end of the shocks and see what happens when the supports are removed.

Offline VileZambonie

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Re: K20 4" lift- Shock issues
« Reply #4 on: April 11, 2018, 07:40:02 PM »
Basically you need to measure the distance with the shocks disconnected from eye to eye at ride height. That is your normal length. Then determine the fully extended length you need (jack it up and let the suspension hang, measure again and then calculate what your compressed length should be. Then you can select the correct shock part number for each position for whatever type of shock you prefer. 
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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline 1967KaiserM715

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Re: K20 4" lift- Shock issues
« Reply #5 on: April 13, 2018, 05:31:51 AM »
Where did you lift the truck from? Lifting from under the axle tubes means the suspension won't flex, like if your lifting from the frame.

This doesn't mean your shock are correct, they could still be wrong for the application.

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Current Vehicles:1985 GMC K10(Daily) 1991 GMC K2500(Daily) 1975 Beetle(not running) 1985 Mercedes 300D(not running) 1952 M35    1967 M715(not running)
 1986 Chevy K30(under repair)