vibrations?

[jks67ss396]

Hey guys

Im trying to see if i have an issue with my 5.3/4l60 or not

this doesnt happen if the truck is in park and i just rev the engine, so i dont think its engine

When driving the truck, there seems to be a certain resonant frequency/rpm that i feel slightly through the dbw pedal when i get on it a little. its probably the whole truck, but i feel it more in the pedal instead of the carpeted floor.

its not so much of "uh oh, something is wrong" as more of a "hey this thing has some b@lls"

if i let off the gas, the slight vibration goes away, get back on it, it comes back.

but as i gain speed, it goes away

its a 2 piece driveshaft

Ive checked motor mounts, trans mounts, ujoint strap bolts, greased all ujoints, checked exhaust bolts (have those layered rubber isolator hanger straps)

trans fluid is new, new filter, correct fluid level, external cooler

is this something on trans? something with 2 piece shaft? normal?

i would expect this kinda vibration through a throttle rod connected big block or if i have a misadjusted throwout bearing on a mechanical clutch, but not a dbw 5.3

thoughts? or your own experiences?

thanks guys!

[solidaxel]

Originally Posted by jks67ss396

Hey guys

Im trying to see if i have an issue with my 5.3/4l60 or not

this doesnt happen if the truck is in park and i just rev the engine, so i dont think its engine

When driving the truck, there seems to be a certain resonant frequency/rpm that i feel slightly through the dbw pedal when i get on it a little. its probably the whole truck, but i feel it more in the pedal instead of the carpeted floor.

its not so much of "uh oh, something is wrong" as more of a "hey this thing has some b@lls"

if i let off the gas, the slight vibration goes away, get back on it, it comes back.

but as i gain speed, it goes away

its a 2 piece driveshaft

Ive checked motor mounts, trans mounts, ujoint strap bolts, greased all ujoints, checked exhaust bolts (have those layered rubber isolator hanger straps)

trans fluid is new, new filter, correct fluid level, external cooler

is this something on trans? something with 2 piece shaft? normal?

i would expect this kinda vibration through a throttle rod connected big block or if i have a misadjusted throwout bearing on a mechanical clutch, but not a dbw 5.3

thoughts? or your own experiences?

thanks guys!

Let me know when you find and fix it !!!

I have the "same" vibrations while driving, everything checks out OK, but I am still looking for the source.

I have a 1 piece DS and this come in at 1250 to 1350 RPM and is throttle controlled ,in and out, at around those RPM's
New exhaust twice pipes with a crossover and very conservative Walker Muffs
This is a new problem as I have had this truck for 30+ years and it was not there before the swap.
Thanks for bringing this up!

[truckdude239]

where your drive shafts balanced properly? i ahd mine shorthen twice by the same shop and they didn't balance it the second shop that shorted it becasue the frist guy couldn't get it right did balance it

[jks67ss396]

Originally Posted by solidaxel

Let me know when you find and fix it !!!

I have the "same" vibrations while driving, everything checks out OK, but I am still looking for the source.

I have a 1 piece DS and this come in at 1250 to 1350 RPM and is throttle controlled ,in and out, at around those RPM's
New exhaust twice pipes with a crossover and very conservative Walker Muffs
This is a new problem as I have had this truck for 30+ years and it was not there before the swap.
Thanks for bringing this up!

Can you tell me about your setup?
5.3/6.0?
4L60 or 4L80?
What year motor?
DBW, right?

thanks!

[solidaxel]

Mine is the same driveshaft no changes, the U joints are about 2 years old, did not make this vibes before the swap

[solidaxel]

2003 5.3, 4L60E, DBW, all stock, except for the tune.
I loosened up the exhaust and drove it but that did not change anything.
The mounts are DirtyDingo with new rubber, stock stands and they are tight, rear trans mount is new also, X member is moved to the rear 1 3/4 " no other changes and nothing than I can see is rubbing on the chassis.
I had the dog house removed and I did not have any interference with the firewall

[jks67ss396]

ok, so if its not driveshaft, and i dont think its engine (since it only does it when its moving), then im thinking 4l60. be interested to see if a 4l80 would do same thing

Ill see if my vibrations are at the same rpm range yours are.

have you ever taken it to aamco or something for a free diagnosis?

thanks

[BR3W CITY]

What are your pinion angles?

If you don't know....then its probably the problem

My old bagged minitruck used to love to rumble at various heights, because raising and lowering the truck changed the pinion angle.
When you do a swap, depending on the engine and tranny xmember position, and length of the DS, you can end up with a WAY different pinion angle than what you started with. This will wear out ujoints, and in a high hp application can be a huge annoyance.
Does the 2 piece shaft use a carrier bearing?

[jks67ss396]

ill check them tonight/tomorrow. everything on mine is stock suspension. rebuilt and new

i spent a lot of time doing this on my camaro, but with the truck, everything just kinda lined up and didnt look too bad but its worth checking

thanks

[BR3W CITY]

I doubt you can eyeball your pinion angle, but it would be an impressive skill. It's usually a tad forgiving since the 2piece shaft takes up some of the flexion, but its worth looking at. Changing a u joint on the side of the road is a pain.

[solidaxel]

Originally Posted by BR3W CITY

I doubt you can eyeball your pinion angle, but it would be an impressive skill. It's usually a tad forgiving since the 2piece shaft takes up some of the flexion, but its worth looking at. Changing a u joint on the side of the road is a pain.

I checked mine and it is 3* down at the trans and 2* up at the rear end.
Replaced the rear trans mount, and that did not change anything except my wallet is lighter!

[BR3W CITY]

you can change the rear end angle, leave the trans 3* down (meaning the engine is also 3* down, which is good)

[jks67ss396]

i originally did mine like a one piece shaft. thats what i meant by not being too bad. turns out 2 piece shafts require a different procedure. i found a link on this forum to a dana article and checked mine. mine was about 4 degrees off at the rear and 1 degree off at the trans. so i shimmed up the trans and got the front in spec. i ordered some shims from stock car products and they should be here in a couple days.

ill report back when i get them put in

solidaxel... did the rpm of the vibration change after your trans mount swap?

[solidaxel]

Just in my wallet!
My vibration is not in my driveline, when you shift out of gear at speed it goes away.
I can make it vibrate at 1300 rpm sitting still !!
Has to be the engine hitting somewhere, still looking for the cause

[jks67ss396]

ok, see, i dont think mine does it in park. ill check from idle to 2500 tomorrow

did you buy the engine/trans together? ever had them apart from each other?

if you can shift out of gear and make it go away, its gotta be trans, right?

[BR3W CITY]

Originally Posted by solidaxel

Just in my wallet!
My vibration is not in my driveline, when you shift out of gear at speed it goes away.
I can make it vibrate at 1300 rpm sitting still !!
Has to be the engine hitting somewhere, still looking for the cause

flywheel bolt? its a beatch but it happens, especially tho those who had to put the trans on IN the truck.

[solidaxel]

The engine was a take out from a Silverado complete package 72K.
Yes, I have experienced a cracked flex plate, I had not thought of that.
The vibration is not that bad just a certain RPM and tiney!

[jks67ss396]

well, i installed my pinion shims today and took it for a test drive.

the vibration is still there. around 1700rpm. again, its not bad, just noticeable. by 1900 rpm, its gone.

it is not there when the truck is in neutral.

im thinking of having the driveshaft shop take a look at it. they just cut the shaft and balanced it before the swap

any other ideas?

[jks67ss396]

So ive tracked my vibration down to something in the vintage air/kwik performance install. decided to take off the ac compressor and brackets and put the stock tensioner back on, vibration gone. Put the brackets and compressor back on, vibration comes back. compressor is not charged, just spinning freely with the engine.

im thinking tensioner or this idler pulley that comes on the kwik setup

any of you guys have experiences like this?

thanks

[69sinker]

Glad you found the problem, but I hate to hear that's what it was. I'm putting on the same setup this weekend. I'll let you know my results. How long has it been on there? Dave

[jks67ss396]

well, my story starts with the fact that the camaro tensioner that kwik specified stuck out way too far. this was a delco part. so wayne sent me a corvette tensioner and spacers. i did find a belt that works. napa 113" made by gates.

but the vibrations are annoying.

I talked with a dayco tech today about resonant freqs and how changing belt length between pulleys/tensioners etc can change freqs.

Ive ordered a shorter belt and im going to pull the top idler pulley off and run without it. hopefully the longer belt span from alternator idler to compressor will change the resonant freq of the system to something a little lower.

with a 373 and my tires, 1600 is right at 55 in 4th gear.

ill post results here.