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Old 10-26-2016, 08:09 PM   #1 (permalink)
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How effective is it to set drivetrain back in chassis

So I am almost ready to start linking out my truggy. It's currently 116" wheelbase based on a k30. Can is in stop location, front in traditional 56" stretch. Let's say axle centerline is 1-2 cylinder. In an attempt to reuse some shock mounts, gain a better approach etc, I figure on stretching the front 4".

Obviously I do not want 120" wheelbase. So that leaves bringing the rear forward (this wil get linked first). I figure I can bring the rear 4-5" forward and not suffer too much on driveline angles.

So my question is how much would this improve or effect the performance to the truck? It would effectively put the axle under the crank pulley. Is it worth all that ir shorten the rear for better wheelbase etc?
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Old 10-26-2016, 09:28 PM   #2 (permalink)
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Why do you obviously not want a 120" wheelbase? That's what my yota was and I loved it.
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Old 10-26-2016, 09:32 PM   #3 (permalink)
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The more you move the engine/tranny/T-case back and leave everything else the better your weight distribution will get. If I were to do it again I would move the Engine/Tranny/T-case back as far as I can until the rear DS started to suffer. I would prefer to have the front axle about 6-8" in front of the crank pulley.
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Old 10-26-2016, 09:34 PM   #4 (permalink)
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Well if it's not built to cruise big gay truck land then it can be beneficial. What are you intending to use this for? Overall specs besides your WB? Front uptravel? Truss? Drivetrain-doubler? Driveshaft goals?

I'll give you some facts and figures of my old Ford to help. Short story long, my opinion about setting the engine back.

I set mine wayyyyyyyy back. 13" plus a 3.5" front axle stretch. 13" is the number I came up with to place my NP205 output yoke where the carrier bearing was originally after I factored in the 6" from my NWF TITAN. I lowered the drivetrain a little over 1" from where it originally sat in the frame.

Next I designed my links, on paper, a million times. Wanted the fronts same as rear and with my past experience and what generally works well for everyone else, I came up with 40". Angle effects this but you probably already understand that. I wanted my rear links to converge near the output as another consideration. Many hours picturing and planning my proportions as well when figuring length of links, capture points and drivetrain placement when determining WB or vice versa. My rear axle probably went forward 18". The axle is 36" off the back of the cab.

Once you engineer it, reverse engineer it and check it again to see if you like it.

My driveshaft is 28" at ride and only 1" either direction bump to droop. 1410 joints. 6* crankshaft 6* pinion. 6-5/8" vertical offset at ride. Equal length double triangulated rear links. With 17" of available droop the pinion increases to 11* and the max joint angle at the output is 29* and 24* pinion.

Rear output is 25" from ground at ride and front of crankshaft is 34". At full bump (5" uptravel) with a D60 and Artec truss, there is 2.5" between it and the crank pulley.

78" roof height, 20" belly, 28" rockers (shaved) 37" tires

Now mine is low and I wanted interchangeability with links and shafts. I wanted a low and predictable CoG and 60/40 or even 55/45 weight bias. There was a lot of planning to get where I'm at. Since I've wheeled a lot of "stock" full size trucks in my day, I can only imagine how awesome this one will do. To me it should be the epitome of predictable handling. I'll find out soon.

Hope this gives some perspective to your project.

EDIT:

Forgot to mention that my WB is 117.5"
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Last edited by Juicysluice; 10-26-2016 at 09:35 PM.
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Old 10-27-2016, 03:57 AM   #5 (permalink)
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Juiceysluice, my specs are pretty similar. Doubler, midship shaft, 1410s, low belly 20", i want 36" links that would know require 1 spare, 6" up, 8" down. I would me bet you output is 28-30" up.

I think in many ways it would help by having the bias more even. I am not actually moving the drivetrain but more so setting moving the axles forward. As to going to a longer wheelbase, no thanks. Where we wheel I am already a school bus. If I do anything I will lose wheelbase.
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Old 10-27-2016, 09:14 AM   #6 (permalink)
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The balanced bias is going to help in the climbs. (Or jumps) As JHF explained years ago in a great discussion with chassis #'s and how it applied, that weight if it's already and physically rearward then in that "instant" you hit a hill, ledge, obstical the vehicle is much more controllable and will keep the front end down because there won't be an action of instant weight transfer such as the front jacking up and wanting to come over backwards. This applies to the AS #s and also aids or keeps a more constant forward bite on the rear axle. He preferred lower values because the susp stays soft so it won't bounce or hop in climbs but not so low that the susp/springs can't support the weight of the vehicle during this weight transfer. 20-60% shoot for 50% in his words. Mine is 61% rear.

My thread will give you all of the pictures you need to get an idea of the proportions but sounds like setting the engine deep in the cab is not a result you're looking for.
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Old 10-27-2016, 10:05 AM   #7 (permalink)
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no basically front front and rear are roughly stock shortbed wheelbase/location....I added a link to current pics if someone can load them.. but in those pics i am thinking of moving both axles forward 4-5".....effectively moving the drivetrain more to the center of the chassis....
https://www.pirate4x4.com/forum/chevy...uspension.html
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Old 10-27-2016, 10:51 AM   #8 (permalink)
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That would work. Effectively what the Yeep crowd does but without getting cozy with the engine.
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