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Kinda stumped


Carnes84

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Something Evel Knievel would do when he was  jumping.Here they are for your 81 Datsun 4x4.Rancho doesn't have back one's for your's.https://www.oreillyauto.com/detail/c/rs5000x-series/rancho-rs5000x-series-shock-absorber/ranc/rs55605/v/a/8237/automotive-truck-1981-nissan-720-pickup?q=shocks&pos=9

Edited by Thomas Perkins
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4 hours ago, datzenmike said:

They are all oil filled and hydraulic aren't they? Pressurized with Nitrogen gas to reduce foaming. That's why they extend when relased.

The Rancho 5000 series is hydraulic, but the 5000X is gas.

 

Yes, if they extend when loose, they are gas filled.

 

I'm definitely not saying that hydraulic shocks are better in a truck. They offer less scuttle shake, but don't corner respond as quickly as gas shocks. Which is exactly why they keep the scuttle shake to a minimum. The loose hydraulic fluid allows the piston to move more before it responds.

 

If you don't know what scuttle shake is, it is when you hit bumps at high speed and the chassis shakes so much that the tires can loose grip on the road. When I used to commute to SF from the east bay, there was a spot just outside of the Caldecott tunnel where if you were in the fast lane at the first left turn after the tunnel, the bumps in the road surface would cause me in my 3/4 ton truck to damn near skip into the next lane. The rear suspension just couldn't handle the confusing signals it was getting from the gas charged Bilstein shocks and the soft squirmy-ness of the truck style chassis and stiff rear leaf springs. Hydraulic shocks fixed that.

 

Some suspensions are better at dealing with rapid input than others and unsprung weight factors in, so an independent suspension, with lighter components, may be better with gas shocks while a solid axle, with heavy components, may be better with hydraulic shocks. You have to consider that all that unsprung weight is trying to bounce back up into the truck at higher speeds. Offroad racing trucks use bypass shocks with bypass valves set to blow off at certain pressures so they don't push back so hard when you're hitting huge washboard or landing a jump. They are tuneable with stacks of shims and external valves that allow you to loosen or firm up the response time. Keeping the tires in contact with the road surface is the best way to keep the power down...and win the race.

 

It's really trial and error though. There is no right answer for every truck.

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On 9/10/2022 at 8:23 AM, ]2eDeYe said:

Welcome to ratsun.

That is a product of the 1980's lol. Do you know if the original shock tower was removed?

Thanks btw I've been a long time reader of the posts on here. Decided it was time to start asking questions.

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