rear suspension

[wibilly]

anyone know how far the rear end will move to the rear on a 3/4 ton leaf suspension when loaded hevaly. i,m trying to fit a 40 gallon fuel tank,blazer skid plate and a reciever hitch up under a short 4x4 and want to make sure i have enough clearance between 3rd and tank and skid plate , but no more than necassary to keep the hitch tucked under as far as i can to not create any extra leverage on susspension thanks

[wibilly]

anybody? i know it moves and i know it moves less than the slip joint splines. but how much do you think 1/2 inch ? 1 1/2?

[LONGHAIR]

It's simple geometry.

Measure the distance from the center if the front bushing of the trailing arm to the center of the axle. Then measure the distance from the axle to the rubber bump-stop. Then you can make a simple tool to measure it and see it with you own eyes.

Cut to straight sticks (2x4s or whatever you have) that are a few inches longer that the previous trailing arm measurement. Line them up, one on top of the other and drive a nail thru them so that it is the same distance from the end as the measurement (A). They will then open forming a V from that point. Now place them on the edge of a work bench/table, line the bottom one up with the edge of the table. Open the other one to the distance of the bump-stop(B). Now the measurement from the opened piece to the edge of the table is how far your axle will move(C).
Here is a picture to explain it a bit better..........

[wibilly]

great idea except i have leaf springs

[ChevLoRay]

Somebody correct my thinking, if I'm wrong, but you have to think that it won't move anywhere near enough to let the slip yoke come out of the tailshaft, or the front drive shaft. With that said, you can look at the slip yoke and see how much of it is shiny, and that should tell you how much movement there is in the driveline, which should include some minor movements of the engine mounts and the transmission...unless they're on solid mountings.

Since you have leaf springs, I am of the opinion that movement would be minimized, compared to the trailing arm set up that I have on my truck. If you're concerned with the punkin' hitting the gas tank, see about locating one of the thick plastic shields that FoMoCo installed on early Pinto's. It was designed to prevent the gas tank from being punctured by the rear axle, in a rear end collision. Didn't help the Firestone 500 tire issue, though.

I don't think you'll find much movement to worry with, as long as you have a couple inches between the tank and anything that moves in normal suspension travel.

Again, this is my opinion, based on my (ample) gut feelings and after having worked under more than a couple cars on racks. It may be totally wrong, but I feel good about what I have said, until someone with more experience proves me wrong. Tread lightly.

[LONGHAIR]

Oops, my fault.......I missed that. It would have saved all of that typing. The travel from the leaf spring (especially on a 3/4 ton) would be so little that I wouldn't even concern myself about it...............

[Longhorn Man]

Why are we talking 3/4 ton on a K/10?

[wibilly]

thanks longhair thats kinda what i was thinking but wanted another opinion suspension must be compresed 2" before it would cause any interfearance then i moved tank and skid plate back so there is about 1" between rear end and skid plate and another 1' between skidplate and tank i'll try this if i have to i can always reshape skid plate in the center for more clearance. i had to extend the frame about 2" to make it all fit and use the reciever i had but i think i got it all worked out now just need to reverse tabs on the blazer skid plate so it can be removed easaly. dont know what those engeners at gm were on the day they designed them

[wibilly]

it's a shortened k20

[CochinoFilipino]

If you pull a tape along the arc of the spring from the pivot to the axle you get the max length of the leaf. The leaf will straighten but it's not going to stretch. And go from there.