Extreme Drops

[firedog]

my truck is a driver also (only on a trailer when its broken) love cruising around as low as i can in my truck... drove it to midwest all truck nats from stl to kc and back and i think it rides better on air then it did from the factory

[bedsled71]

can you explain why there would be a problem with vibrations with the driveshaft on an incline since the vibrations are caused from the angles of the ujoints working aginst eachother? or is that not correct?

[bedsled71]

can you explain why there would be a problem with vibrations with the driveshaft on an incline since the vibrations are caused from the angles of the ujoints working aginst eachother? or is that not correct?

[SCOTI]

Originally Posted by bedsled71

can you explain why there would be a problem with vibrations with the driveshaft on an incline since the vibrations are caused from the angles of the ujoints working aginst eachother? or is that not correct?

Driveline vibrations can be caused by several different factors. From what I've learned: the operating angles are the primary culprit; then phasing, & then "secondary couple loads".

Secondary couple loads brief explanation from Greg Frick @ IEDLS: These loads operate at 90 degrees to the shaft. With equal and opposite angles these loads cancel out and are not an issue. When the angles are equal, but both on the same side of the drive shaft (the top in my case), they add up. The result of additive secondary couple loads is a shaking of the mounts: the transmission and the rear end. This shaking goes everywhere in the car and is very aggravating.

An odd feature of the secondary couple load problem is that the farther they are apart the less of a problem they seem to be. Unfortunately there is no rule on how far is far enough or how close is too close. What works in a '53 Studebaker will not work in a bucket T.

I have asked more than once for an explanation on the inclined driveshaft issue but haven't gotten any solid feedback. IEDLS has reference material that only states that is the one orientation to avoid. As far as I can tell, the main reason is because that configuration yields excessive working angles for the u-joints. Pages 3-4 explain some typical variations on driveline set-ups:
http://www.iedls.com/asp/admin/getFi...&TID=28&FN=PDF

[PBFAB.COM]

One thing we must all remember when dealing with "customized" and "altered" trucks, chassis, suspension, drive-trains, etc. is that there is no longer a perfect world scenario. If we were to drive vehicles that were set up according to spec. in its "perfect" form... they would no longer be appealing to us.

Once we have voided our factory warranty by modifying our ride, we must look at our game plan from a different angle (pun intended). We must find the compromise, that allows us to accomplish the MOST of what we want (sometimes we get lucky and accomplish ALL of what we want, but this is not always the case). This may mean that we get conflicting or unclear information from different sources... even professionals. Heck, I could go and see three different doctors for the same illness and be prescribed three seperate remedies! This is just how it goes. And why is it that whenever I call and talk to a wheel manufacturer that they can never tell me the backspacing I need... don't they make wheels and sell them everyday? Oh, they just don't want to be liable and responsible if it doesn't work out and the customer isn't satisfied.

Scoti- In your case, your driveline will always slope up in the rear... it's just going to be that way unless you raise your truck another 4"-6". So, what can be done? One real world solution I have recommended and used is a CV or Double Cardon Joint. This will allow the angles to cancel eachother out... no vibrations. I know your drive-line guys told you that's just a band-aid fix... but what other alternatives are there at this point? Maybe raise the truck? (Please don't take this wrong, as we are friends and we talk frequently discussing all sorts of truck related items... I am just using this scenario as an example).

[SCOTI]

Originally Posted by porterbuilt

One thing we must all remember when dealing with "customized" and "altered" trucks, chassis, suspension, drive-trains, etc. is that there is no longer a perfect world scenario. If we were to drive vehicles that were set up according to spec. in its "perfect" form... they would no longer be appealing to us.

Once we have voided our factory warranty by modifying our ride, we must look at our game plan from a different angle (pun intended). We must find the compromise, that allows us to accomplish the MOST of what we want (sometimes we get lucky and accomplish ALL of what we want, but this is not always the case). This may mean that we get conflicting or unclear information from different sources... even professionals. Heck, I could go and see three different doctors for the same illness and be prescribed three seperate remedies! This is just how it goes. And why is it that whenever I call and talk to a wheel manufacturer that they can never tell me the backspacing I need... don't they make wheels and sell them everyday? Oh, they just don't want to be liable and responsible if it doesn't work out and the customer isn't satisfied.

Scoti- In your case, your driveline will always slope up in the rear... it's just going to be that way unless you raise your truck another 4"-6". So, what can be done? One real world solution I have recommended and used is a CV or Double Cardon Joint. This will allow the angles to cancel eachother out... no vibrations. I know your drive-line guys told you that's just a band-aid fix... but what other alternatives are there at this point? Maybe raise the truck? (Please don't take this wrong, as we are friends and we talk frequently discussing all sorts of truck related items... I am just using this scenario as an example).

As I mentioned, I'm confident in your recommendation per our discussions. I also wanted a 'fudge' factor built-in so I have the ability (if possible) to adjust the angles just in case.

I currently have it set-up w/2.5° @ the trans & 2.2~2.4° down @ the pinion w/the d.shaft slightly sloping down. I haven't gotten over to the truck to measure & see how much material out of the floor this would require removing. This would be my alternative if the numbers we discussed (3° down @ tailshaft, CV @ trans, & as close to 0° @ the pinion as possible) doesn't work.

[502ss]

Originally Posted by bedsled71

can you explain why there would be a problem with vibrations with the driveshaft on an incline since the vibrations are caused from the angles of the ujoints working aginst eachother? or is that not correct?

This should explain it.

http://www.hotrodhotline.com/md/html..._harmonics.php
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[SCOTI]

Originally Posted by 502ss

This should explain it.

http://www.hotrodhotline.com/md/html..._harmonics.php
Posted via Mobile Device

Actually, that only explains the equal but opposite need for the cancellation of the angles to eliminate the possibility of vibrations (it also states the d.shaft should be sloping down approx 1°).

My buddy also questioned how the d.shaft knows whether it's sloping up or down thus it shouldn't make a difference.

This is why I stated earlier that the 'difference' would be that when the shaft slopes upward to the pinion, you calculate the angles differently. The result is typically excessive angles that are nearly impossible to cancel thus why I feel they recommend it to be avoided.

[crawdadfox]

Hey Scoti how far from Dallas to Columbus....y'all only have about six months!

[SCOTI]

Originally Posted by crawdadfox

Hey Scoti how far from Dallas to Columbus....y'all only have about six months!

17hrs straight through..... been there & done it so I know what to expect. This truck will make that drive.

[502ss]

Originally Posted by SCOTI

Actually, that only explains the equal but opposite need for the cancellation of the angles to eliminate the possibility of vibrations (it also states the d.shaft should be sloping down approx 1°).

My buddy also questioned how the d.shaft knows whether it's sloping up or down thus it shouldn't make a difference.

This is why I stated earlier that the 'difference' would be that when the shaft slopes upward to the pinion, you calculate the angles differently. The result is typically excessive angles that are nearly impossible to cancel thus why I feel they recommend it to be avoided.

Then here is some more.....

http://www.drivetrain.com/parts_cata..._problems.html
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[SCOTI]

Originally Posted by 502ss

Then here is some more.....

http://www.drivetrain.com/parts_cata..._problems.html
Posted via Mobile Device

Quoted from that source:

When the slopes are in the Same direction on two connected components, Subtract the smaller number from the larger to find the u-joint operating angle. When the slopes are in the Opposite direction on two connected components, Add the measurements to find the u-joint operating angle.

This would mean if the trans is angled down & the d.shaft slopes up, you would add the angles to arrive @ the working angle of the joint. We'll say the trans is @ 3°dn & the shaft is 2° up: 3+2 = 5° working angle.

If the driveshaft is sloping down from the pinion & the pinion is angled down, you would subtract the angles. We'll say the d.shaft is @ that same 2° up & the pinion is 3°dn: 3-2 = 1° working angle.

The numbers yield a 4° difference.

[Mkcustums]

SCOTI -

I know this isn't a Chevy but the point still stands the same... I bought a Hardbody ('97) brand new with 3 miles on it. When it had only 794 it was in my garage on jack stands getting a static drop with the frame 2 1/4" off the ground, that's pretty low. Driveline was pointed up for sure! I put lots of trips on the truck around 700 miles or so with zero issues ever. Sold the truck with over 24k on it and the driveline nor u joints were ever replaced. And no the truck was not abused either, no dents, scratches, or stains. -The driveline angles might never be completely perfect but you can make it work. I think the driveline companies might be scaring you a little bit.

Like you said, do it right the first time and it will be just fine!

[tech@scottshotrods]

heavey metal that Justin Drove 2300 miles each way from Ventura, CA to Indianapolis, IN

[SCOTI]

Ok, I knew what vehicle you were talking about.

[tech@scottshotrods]

Originally Posted by SCOTI

Ok, I knew what vehicle you were talking about.

many don't though so i threw up a few pics

[Scottshotrods]

Originally Posted by SCOTI

Ok, I knew what vehicle you were talking about.

That is so cool you knew that but we figured to show all people that do not know.You can drive a full blown show truck across country .
Justin

[OARNGESI]

Originally Posted by jon@scottshotrods

heavey metal that Justin Drove 2300 miles each way from Ventura, CA to Indianapolis, IN

was that truck built on tv
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[Scottshotrods]

Originally Posted by OARNGESI

was that truck built on tv
Posted via Mobile Device

Yes it was built it in 90 days and took it to detroit then drove it to
Gm in detroit in the freezing ass cold weather.lol
Justin

[Scottshotrods]

What happen guys nobody wants to come out and play!
Justin

[Mkcustums]

Originally Posted by Scottshotrods

What happen guys nobody wants to come out and play!
Justin

Yeah, I'm surprised this thread isn't a lot more active than it is.

[PBFAB.COM]

It would be cool to see some "action" shots of Heavy Metal out on the Interstate! I think I remember hearing it even rained on you guys.

[tech@scottshotrods]

Originally Posted by porterbuilt

It would be cool to see some "action" shots of Heavy Metal out on the Interstate! I think I remember hearing it even rained on you guys.

I remember seeing it in indy looked like a swiming pool and justin didnt care LOL interior was replaced i think 2-3 times due to un foreseen rain storms

[killer71]

ken, do you have any side shots of that truck so that the wheels can be better seen?

[N2TRUX]

Originally Posted by killer71

ken, do you have any side shots of that truck so that the wheels can be better seen?

Lets see what I have...