Desperation equals dumbass ideas

[leversole]

Desperate to figure out what is making my truck bounce...I came up with an idea to check the rear rears to see if they were causing it, also, this would check to see if the "peanuts" were the root cause. My plan was to chain the rear rear up off of the ground and go for a drive...

Okay, I thought, this idea is dumb, but is it just a dumb idea, is it an idea that will get me hurt, or is it an idea that will break something major...anyhow, I decided is was just a dumb idea so I tried it...

Got the rear rear jacked up and chained it up so that the rear tires were off the ground by a few inches. I knew they would drag where my driveway meets the street, but I figured I would release the parking brake and let it roll into the street...so far so good...I got about 1 mile from the house, not yet having a chance to get to "bounce speed" when the chains shifted, stretched, whatever the case, the rear tires dropped down and partially contacted the road and the front rear or transmission started growling and shaking...got it stopped pretty quick...I was on a slight hill, and the tires were not up high enough to slip on the road with the park brake on, and not getting enough traction to move the move truck with the brake off....couldnt even set the parking brake as the truck kept rolling (slipping the rear tires)...to make a long story short, I got it chocked and because I was smart enough to bring the hydraulic jacks just in case, I got the rear end back on the ground...then drove around a while to make sure no strange noises...so back at square one...

[Rob]

Desperate to figure out what is making my truck bounce...I came up with an idea to check the rear rears to see if they were causing it, also, this would check to see if the "peanuts" were the root cause. My plan was to chain the rear rear up off of the ground and go for a drive...

Okay, I thought, this idea is dumb, but is it just a dumb idea, is it an idea that will get me hurt, or is it an idea that will break something major...anyhow, I decided is was just a dumb idea so I tried it...

Got the rear rear jacked up and chained it up so that the rear tires were off the ground by a few inches. I knew they would drag where my driveway meets the street, but I figured I would release the parking brake and let it roll into the street...so far so good...I got about 1 mile from the house, not yet having a chance to get to "bounce speed" when the chains shifted, stretched, whatever the case, the rear tires dropped down and partially contacted the road and the front rear or transmission started growling and shaking...got it stopped pretty quick...I was on a slight hill, and the tires were not up high enough to slip on the road with the park brake on, and not getting enough traction to move the move truck with the brake off....couldnt even set the parking brake as the truck kept rolling (slipping the rear tires)...to make a long story short, I got it chocked and because I was smart enough to bring the hydraulic jacks just in case, I got the rear end back on the ground...then drove around a while to make sure no strange noises...so back at square one...

I don't think it was a dumbass idea but am surprised it worked. I would have thought the torque bias would have been routed to the axle that is off the ground causing it to spin. Of course with you not hammering the throttle there was probably enough preload to not let it slip. I'll bet if you would have asked for hard acceleration it would have been really loud as the peanuts started skipping from the slip of breakover torque.

Rob

[leversole]

I don't think it was a dumbass idea but am surprised it worked. I would have thought the torque bias would have been routed to the axle that is off the ground causing it to spin. Of course with you not hammering the throttle there was probably enough preload to not let it slip. I'll bet if you would have asked for hard acceleration it would have been really loud as the peanuts started skipping from the slip of breakover torque.

Rob

I had the rear brakes locked...that's how I got it to move...had I released the brakes, I would have went nowhere! I figured if I moved it with the rear driveshaft not turning, all of the torque would route to the front and the peanuts would not be trying to dig in and engage, which may have been causeing the truck to bounce...that was my theory anyhow!

[Rob]

I had the rear brakes locked...that's how I got it to move...had I released the brakes, I would have went nowhere!

That makes sense. Your spring brakes are on the rear drive?

Rob

[leversole]

That makes sense. Your spring brakes are on the rear drive?

Rob

Yes...on the rear...

[Rob]

Yes...on the rear...

I can't reason that this would do any good on mechanical parts involved. The inter axle power divider would be 100% slipping all the time and this would seemingly rapidly cause wear to the cam and plungers from this slippage. I may be incorrect but it sure seems this thing is going to try to keep the differentials together.

Rob

[leversole]

You are right of course, my reasoning was that if the power divider was jumping in and out at a certain speed, and my tires were average different diameters front to rear, this might be the cause of the bounce as the frame is loaded and unloaded rapidly...it was just a test, as I am sutck unless I starts chainging BIG parts!

I was thinking of having it towed with the front end up to eliminate or confirm that the front end is causing the issue...lots of wasted money on that though!

[Rob]

You are right of course, my reasoning was that if the power divider was jumping in and out at a certain speed, and my tires were average different diameters front to rear, this might be the cause of the bounce as the frame is loaded and unloaded rapidly...it was just a test, as I am sutck unless I starts chainging BIG parts!

I was thinking of having it towed with the front end up to eliminate or confirm that the front end is causing the issue...lots of wasted money on that though!

Has anyone ran "chase" with you yet at the speed in question? It may jarr your teeth to maintain a speed that is shaking the truck apart but a lot can be learned with somebody actually watching the driveline and tires from outside as the vehicle is operated.

The drive tires really do need to be within 1/2" diameter of each other on the rears to not induce problems and if yours are different in height by much, they need changed. I never really put a lot of thought to it until your photo of the axle chained up. I was thinking since you replaced them, they all matched.

Rob

[leversole]

Have been going to get my wife and son to video in "chase" mode from different angles...unforturnatly, only six of the eight rear tires match, two are a different brand, BUT. the problem was happening before the new tires, not to say I didnt "swap" the same problem between the old and new tires...

[Rob]

Have been going to get my wife and son to video in "chase" mode from different angles...unforturnatly, only six of the eight rear tires match, two are a different brand, BUT. the problem was happening before the new tires, not to say I didnt "swap" the same problem between the old and new tires...

They really don't have to match as far as tread design. They do need to be round with no flat spots, (as in skidded) or out of round. They must be the same in diameter on all four corners.

Rob

[Green Dash]

I wish I were enough of a dumbass for it to not require 3 read-throughs for me to understand what the hell you're talking about.

[Rob]

I wish I were enough of a dumbass for it to not require 3 read-throughs for me to understand what the hell you're talking about.

I'm just babbling myself. Hope somebody is smart enough to figger it out.

Rob

[fxfymn]

I think there is a special place in hell for all of us that are trying to chase down unknown shakes and rattles. At the Spring Melt I had the chance to ask Cal Little about the drive line noise I have in the 52. He went through the usual litany of rear differential (already rebuilt), transfer case (ditto), driveshaft, etc. When I told him why I had ruled out all those he just said what we all know "Strange noises and shakes can really be tough to find and sometimes you never do find 'em."

I hope you figure it out.

[Rob]

I think there is a special place in hell for all of us that are trying to chase down unknown shakes and rattles. At the Spring Melt I had the chance to ask Cal Little about the drive line noise I have in the 52. He went through the usual litany of rear differential (already rebuilt), transfer case (ditto), driveshaft, etc. When I told him why I had ruled out all those he just said what we all know "Strange noises and shakes can really be tough to find and sometimes you never do find 'em."

I hope you figure it out.

I have seen driveline noise propagate through the driveshafts and bearings. There is actually a product that "foams" the inside of a driveshaft that is very effective. This usually cancels out "ringing" that is sometimes heard under acceleration when loaded.

Many manual transmissions of yesteryear use gearsets based on the 14 degree contact pressure angle. These are very strong in application but noisy in operation. This is part of the whine you hear from drivelines. Heavier weight gear oil is usually the solution for this.

Rob

[fxfymn]

Thanks for the help. Noise sounds like diamond plate rattling, but only occurs in high (fifth over) gear when I slack off the accelerator. Noise is louder as the truck goes faster, but does not occur at the same speeds when I am not in high gear. (In 4th @ 50 MPH no noise; in 5th @ 50 MPH the noise is there)

Don't feel any vibrations in the gear stick. What is strange in my mind is the twin truck to mine does exactly the same thing and the owners of that truck haven't been able to find the source either.

I have had the cover off the tranny and everything looks really good; no shavings, gears turn smooth as butter. I'm running 85-140 in the tranny now. Suggestions for a change?

[Rob]

Thanks for the help. Noise sounds like diamond plate rattling, but only occurs in high (fifth over) gear when I slack off the accelerator. Noise is louder as the truck goes faster, but does not occur at the same speeds when I am not in high gear. (In 4th @ 50 MPH no noise; in 5th @ 50 MPH the noise is there)

Don't feel any vibrations in the gear stick. What is strange in my mind is the twin truck to mine does exactly the same thing and the owners of that truck haven't been able to find the source either.

I have had the cover off the tranny and everything looks really good; no shavings, gears turn smooth as butter. I'm running 85-140 in the tranny now. Suggestions for a change?

Hi Carl, this sounds like gearset wear to me. Overdriven transmissions are always hard on that gearset no matter the horsepower or torque rating of the engine. You might try to wrap the transmission in a blanket to see if the noise is attenuated. Don't do this long as the heat will not be rejected from the operation. This is only an isolation method. Another source of noise is slip/spline wear in the driveshafts. This can usually be attenuated by greasing heavily and test driving although it always returns.

Rob

[lucerne tractor]

My R611 always had a bounce a a certian speed. I had all new king pins , bearings, aligned by the best, spun balanced new Generals on front, spun balanced new drives, never could find it.

[fxfymn]

Hi Carl, this sounds like gearset wear to me. Overdriven transmissions are always hard on that gearset no matter the horsepower or torque rating of the engine. You might try to wrap the transmission in a blanket to see if the noise is attenuated. Don't do this long as the heat will not be rejected from the operation. This is only an isolation method. Another source of noise is slip/spline wear in the driveshafts. This can usually be attenuated by greasing heavily and test driving although it always returns.

Rob, Thanks so much. I'm positive it is in the tranny since it only occurs in fifth and when I removed the floor the sound diminished due to what I believe was the lack of the "diaphragm" effect from the floor. I will definitely try the idea of muffling the sound with some type of insulation to see if that diminishes the noise.

I have thought for some time that the noise is related to some type of excessive gear lash since it only occurs under a “no load” condition. Is it possible to shim the shaft to take the excessive play out of it?

[Rob]

Rob, Thanks so much. I'm positive it is in the tranny since it only occurs in fifth and when I removed the floor the sound diminished due to what I believe was the lack of the "diaphragm" effect from the floor. I will definitely try the idea of muffling the sound with some type of insulation to see if that diminishes the noise.

I have thought for some time that the noise is related to some type of excessive gear lash since it only occurs under a “no load” condition. Is it possible to shim the shaft to take the excessive play out of it?

If it is teeth wear, no. It would take mating gear replacement to close the clearance that has developed through years of use. If a bearing worn; maybe. Could also be internal, and external wear to the sliding clutches also. Either way requires a rebuild of the transmission which is not difficult if parts can be located.

I have the same thing with a 6231 Brown-Lipe progressive auxiliary transmission from my A40. It is a real "singer" in O.D. but perfectly quiet in the other two gears. I pulled it out and replaced it with a low gearset 6231 as it was all I could find. I've kept the original as my truck was built with it and hope to someday find a couple of gears.

Rob

[fxfymn]

I had pretty well decided to live with it until it breaks while I looked for a replacement tranny. Given that it's mate does the same thing, even a replacement may have the same issue. Thnks again. Stop by and say hello in Macungie and if we can get off the grounds I'll take you for a spin to see what you think in person.

[Rob]

I had pretty well decided to live with it until it breaks while I looked for a replacement tranny. Given that it's mate does the same thing, even a replacement may have the same issue. Thnks again. Stop by and say hello in Macungie and if we can get off the grounds I'll take you for a spin to see what you think in person.

Thanks and I plan to look up everybody that can stand to the smell of me.

Rob