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TKO 3rd gear vibration

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railing68

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Discussion starter · #1 ·
Noticed this over the past couple of drives:

High RPM above 5400 in 3rd, (major shifter stick buzz) best explanation I can think of.

I don't notice it in 1st or 2nd, but it isn't at that rpm very long at full throttle.

It is not easy to test for this problem due to the high speeds associated with 3rd gear at this rpm.

I am probably going to have the driveshaft rebalanced, and definitely go through the undercarriage, mounts, etc... and check for loose bolts.


Had it on a road course and saw this kind of high speed/rpm repeatedly about 1.5 years ago and I don't recall the vibration, but there was a lot going on at the time.

Any other suggestions?

Thanks, SS
 
#2 ·
First thought is , Was bellhousing dialed in? Second would be pilot bearing but then you said it only does this in 3rd? How are your drive line angles?
 
Discussion starter · #3 ·
Was dialed within .003, angles are currently unknown I am getting a tool most likely today to check.

Took the driveline down to the best place in town(different than last place) and upon balancing they stated: yokes were welded out of time(not same spot rotationally on the shaft) and there was no weight on it from when I had it shortened for the TKO a couple of years ago.

Hopefully that was the culprit (yokes that is)

If it was an indexing issue wouldn't show up in 4th gear or somewhere else...
Really hard to tell on the street especially w/o getting in trouble!

I love doing things twice, the quality of work these days for a lot of places $ucks,

Thanks, SS.
 
#4 ·
railing68 said:
Was dialed within .003, angles are currently unknown I am getting a tool most likely today to check.

Took the driveline down to the best place in town(different than last place) and upon balancing they stated: yokes were welded out of time(not same spot rotationally on the shaft) and there was no weight on it from when I had it shortened for the TKO a couple of years ago.

Hopefully that was the culprit (yokes that is)

If it was an indexing issue wouldn't show up in 4th gear or somewhere else...
Really hard to tell on the street especially w/o getting in trouble!

I love doing things twice, the quality of work these days for a lot of places ,

Thanks, SS.
Click to expand...
Stay with it, my thinking is something other than drive shaft , just as you said, it only occurs in 3rd gear, but I need to ask, 3rd gear under power? Cruise? or Decell?

I have such a problem and suspect drive line angles. I just use the generic Johnsone angle finder (HarborFreight) and found my u-joint angles off, from each other.
In order to correct the rear angle, I had no choice other to tilt pinion nose down as I reached all I could out of transmission tilting.
GMJim, has a good topic about this issue here. If you do a search under "driveline angles" , you should find it. Keep in touch.
 
#5 ·
railing68 said:
Noticed this over the past couple of drives:

High RPM above 5400 in 3rd, (major shifter stick buzz) best explanation I can think of.

I don't notice it in 1st or 2nd, but it isn't at that rpm very long at full throttle.

It is not easy to test for this problem due to the high speeds associated with 3rd gear at this rpm.

I am probably going to have the driveshaft rebalanced, and definitely go through the undercarriage, mounts, etc... and check for loose bolts.


Had it on a road course and saw this kind of high speed/rpm repeatedly about 1.5 years ago and I don't recall the vibration, but there was a lot going on at the time.

Any other suggestions?

Thanks, SS
Click to expand...
Third gear at 5400 rpm. What is the speed? Try driving at the same speed in 4th or 5th gear. If it's drive shaft related it will vibrate at the same driveshaft rpm. If it's engine it will vibrate at 5400 rpm in every gear but will differ depending on load. This one may be a little tough to solve but eliminate one thing at a time.
 
Discussion starter · #6 ·
Speed is 77-87mph from 5500-6250 according to calculator and this is about right.

THis is under WOT in 3rd, where the vibe occurs and its substantial.
Under moderate throttle in third to 5200+ no vibration, not in 4th or 5th either to my recollection but I will test it ASAP when safe...

As I said seems to only be in 3rd.

In speaking with the driveline shop where I just spent $80 on re align, rear ujoint(wasn't bad but bought a better one) etc..
He stated driveline has a max rpm say 10,500 and at half that there could be a harmonic disturbance for lack of a better term.

Hard to say, but I know I don't feel it in first or second, just third, and to get to that rpm in fourth or 5th is asking to go to jail on the street.

Let alone third, I am checking angle with the harbor frt tool shortly and will post them

I get a difference of roughly 87-85.5* a difference of 1.5-2*. which is within tolerance according to the shop.

Driveshaft rpm is not the same in other gears as third is at this particular rpm, according to the shop it is slower, I thought it would be faster such as in 3rd 1.43xrpm?

SS.
 
#7 ·
railing68 said:
Speed is 77-87mph from 5500-6250 according to calculator and this is about right.

THis is under WOT in 3rd, where the vibe occurs and its substantial.
Under moderate throttle in third to 5200+ no vibration, not in 4th or 5th either to my recollection but I will test it ASAP when safe...



SS.
Click to expand...
I am trying to break up whats going on here, to see if it means anything and at wot pulling up to 5500 , tells me the pinion nose could be trying to climb up wards, thus creating a very bad u-joint angle? If you feather rpm up slowly, this does not occur? Maybe I am looking for something that really isn't there.
Hope you find something in the driveshaft when you get it back in.
 
#8 ·
Driveshaft rpm is not the same in other gears as third is at this particular rpm, according to the shop it is slower, I thought it would be faster such as in 3rd 1.43xrpm?

SS.[/QUOTE]

The driveshaft RPM is related to the speed the car is going. Depending on the speed, the driveline will be turning the same RPM as it would be in any other gear. Only the engine speed will vary depending on which gear it is in. Does it vibrate at 5400 in any other gear?
 
Discussion starter · #9 ·
To clarify it is at approximately Upper 5k ie. 5400 through redline which is probably 6k in 3rd.

No vibration in 1st and 2nd in the upper rpm range, and 4th is hard to say do to high speeds but I don't think so.

It could very likely be changing the angle due to acceleration however, wouldn't it do this in 1st 2nd as well ???

It just happens more rapidly (maybe that is the key) angle gets to or past that point of issue very quickly in (1st and 2nd) where in third the rpm is sustained for a few seconds... but not sure

I need to get it back together and check it out w/o getting in trouble!

SS
 
#10 ·
railing68 said:
To clarify it is at approximately Upper 5k ie. 5400 through redline which is probably 6k in 3rd.

No vibration in 1st and 2nd in the upper rpm range, and 4th is hard to say do to high speeds but I don't think so.

It could very likely be changing the angle due to acceleration however, wouldn't it do this in 1st 2nd as well ???

It just happens more rapidly (maybe that is the key) angle gets to or past that point of issue very quickly in (1st and 2nd) where in third the rpm is sustained for a few seconds... but not sure

I need to get it back together and check it out w/o getting in trouble!

SS
Click to expand...
The only thing different is the speed. What I'm trying to say is you're going through the rpm range in first, second and third gear but as the car speeds up the vibration comes in at a specific speed. So between 77-87 mph is where you feel it. You only feel it in third gear because that's the gear you're in at this rpm at this specific speed. I think zdld17 may be on the right track with angle change but drive shaft critical speed while under stress might be a factor too?:confused:
 
Discussion starter · #11 ·
Re: TKO 3rd gear vibration UPDATE

I drove it today and ran it hard in the lower gears, hard to tell about the vibe. In third to about 5k+ and it is has changed in frequency to a much slighter and faster oscillation.

Did the same in 4th and felt it so it must be what? Tire balance, or this could be inherent of the chasis since the motor mounts are solid moroso and all bushings in the chassis are solid aluminum and poly trans mount. I Checked motor mounts, trans/crossmember, everything seems tight and fine. Vibe is at 90mph and is not easy to diagnose.

I am not saying it is as bad, but there is some vibe there under 5k in 4th. slight shifter buzz at speed. I don't notice it on decelleration as much, not sure if that means anything.

I didn't really get to rev out 3rd so I am not really convinced the driveline alteration did much of anything. I am by no means freaking out but I would like to address it if possible.

I might have the tires rebalanced but most spin balancers only spin to 60mph right? So that is hit or miss. I don't really want to throw money at a ghost Hmmm.

Drive shaft critical speed could be culprit? Not sure how to address that without incurring a large cost of a new shaft or...

Even though the car is stiff there is some squat and front end lift in higher RPMs (the angle of the ujoints is probably changing at that point)
Any ideas are welcomed, thanks! SS
 
#12 ·
I , keep going back to the rear u-joint angle , under power for your problem. The way I am looking at this is , under WOT first and second gear, you have enough power to rear , to wrap springs up some and get pinion nose up, thus correcting any out of specs u-joint angle.

But in third, the FORCE, at WOT, is not as great so the "out of spec" u-joint angle, does not self correct, the nose stays down. Make sense?

For the cost of spring degree shim, I would make an attempt to bring that pinion nose up a few degrees. I would get car up on jack stands and do some measuring at the rear joint. Take a measure between drive shaft and pinion flange.

I had to lower my pinion nose to get rid of this type of vibration. You may need just the opposite. Hope this helps. Keep in touch.
 
#13 ·
I'm also very interested in this. I had similar shifter buzzing going on on my TKO. Funny thing is that when I first installed the tranny it didn't do this. Took about a year and 5,000 miles before it started. It started in 3rd gear - bzzzzzzz - around 4k rpm. If I put my hand on the top of the shifter it muted it - couldn't hear it. Then later I began hearing it in 4th gear and it began to happen more frequently (at first it was very few & far between). I took off the shifter tower and it just seemed like it had to much play between the pivot points so put a new one on and haven't heard the buzzing. The new one seemed to pivot tighter and was less likely to rattle. The original one would rattle if you shook it. Now based on what you're saying I'm not so sure if either you have a shifter handle problem too or if the shiftter tower was not my problem and the new one may eventually start to vibrate also. Hmmmmmm. I'm definteily interested in hearing more about how you resolve this annoying rattle sound.
 
#14 ·
68RS-SS said:
I'm also very interested in this. I had similar shifter buzzing going on on my TKO. Funny thing is that when I first installed the tranny it didn't do this. Took about a year and 5,000 miles before it started. It started in 3rd gear - bzzzzzzz - around 4k rpm. If I put my hand on the top of the shifter it muted it - couldn't hear it. Then later I began hearing it in 4th gear and it began to happen more frequently (at first it was very few & far between). I took off the shifter tower and it just seemed like it had to much play between the pivot points so put a new one on and haven't heard the buzzing. The new one seemed to pivot tighter and was less likely to rattle. The original one would rattle if you shook it. Now based on what you're saying I'm not so sure if either you have a shifter handle problem too or if the shiftter tower was not my problem and the new one may eventually start to vibrate also. Hmmmmmm. I'm definteily interested in hearing more about how you resolve this annoying rattle sound.
Click to expand...
I too have had this ''buzzing sound" in the stock shifter. I have grown accustomed to it and understood that this could be normal in od or 5th gear. Both my 500 and 600 tko's had this. New shifter huh, keep this in mind when I have to pull again for some other reason. Its not comming out just for this. If I could build me a removable floor tunnel cover, that would help also when I have to lift motor , in the car. Thanks.
 
#16 ·
You may require a more solid mount but try a stock rubber mount to see if the buzzing in the shifter goes away. I had some issues in a Vette that I did and solved all the problems with rubber mounts all the way around. High HP applications need better mounts but you sacrifice other things.
 
#17 ·
I was able to remove my shifter tower w/o pulling or lowering the tranny. I do not have a stock hole but had to cut my own as was converting from auto, however, would think that you could pull the tower (held in place with two allen head bolts) w/o pulling or lowering tranny. I simply had to remove the console and the boot and a custom plate I made which surrounded the hole I cut. That said, I also agree 110% with the comments about ensuring all else is in order. Like I said - so far it has worked for me and I've heard of a couple other instances where this has worked in the C-3 vette forum - which is how I learned about it. It's definitely possible that is not the cause of this post's issue (or others) but worth a consideration. When comparing old and new I realized that the replacement shifter seemed to be built with closer tolerances in the pivot points which is where the metal on metal vibration noise in my case was coming from. Aside form that I couldn't feel the vibration in seat of pants or anywhere else. I have a stock type rubber mount on the tranny and polyurethane everywhere else (body, engine & suspension) The replacement shifter also appeared to have some grease in these areas which the original did not - however it's possible that the grease was there originally but like I said there was no indication that it was. Not trying to stear anyone off course by any means but every now and then you find the problem were you don't expect it.
 
Discussion starter · #18 · (Edited)
The shifter is now a McLeod/B&M slik stix. I don't recall this with the original shifter.
One problem is the stick becomes loose on the shifter arm periodically(happened with both shifters).

I have used lock nuts, loctite, and barbed washers to combat this.

The driveline was just rebalanced with a new rear u installed.

driveline angles differed by no more than 2* (at rest, however this might be changing in third as stated by another member).

I wonder if this is a TKO deal.

Motor mounts are steel, tranny is poly, I might go back to the rubber and see what happens, but it hasn't been rubber since the muncie was in.

I need more seat time and open road to really verify the vibrational symptoms and if they have lessened since the rebalance of the shaft since I only drove it once.

I did notice it at about 4k in 4th, seems to have changed some but hard to tell.

Before the rebalance I could feel the vibe through more than just the stick, the jury is still out since I haven't seen over 5K in third since having the shaft done!

SS
 
#19 ·
railing68 said:
The shifter is now a McLeod/B&M slik stix. I don't recall this with the original shifter.
One problem is the stick becomes loose on the shifter arm periodically(happened with both shifters).

I have used lock nuts, loctite, and barbed washers to combat this.

The driveline was just rebalanced with a new rear u installed.

driveline angles differed by no more than 2* (at rest, however this might be changing in third as stated by another member).

I wonder if this is a TKO deal.

Motor mounts are steel, tranny is poly, I might go back to the rubber and see what happens, but it hasn't been rubber since the muncie was in.

I need more seat time and open road to really verify the vibrational symptoms and if they have lessened since the rebalance of the shaft since I only drove it once.

I did notice it at about 4k in 4th, seems to have changed some but hard to tell.

Before the rebalance I could feel the vibe through more than just the stick, the jury is still out since I haven't seen over 5K in third since having the shaft done!

SS
Click to expand...
Since you mention the shifter stick problem, here is what I did , I have basically a stock Muncie/Hurst round lever, what came with the car. I drilled holes in the flat part , that normally fits in the rubber slots on a stock GM shifter. The drilled hole patten matches the bolt hole pattern on the TKO stock threaded shifter stub. I am using the TKO issued allen pan head bolts with internal star lock washers. I believe these bolts are metric. I have had no bolt loosening at all.

As for mounts, I went to the poly engine mount and had a poly trans mount but it set too high, thus creating a large drive line angle. I went to the stock hollow rubber generic mount (#2268 Anchor). This mount was shorter by about 1/2" when compared to the poly mount.
Some of these vibrations may not be removable. Even when my car was new, I always did seem to have a floor pan vibration that could be felt and seen in the rear view mirror. Being a GM dealer part man, I ordered several drive shafts from sister vehicles that had the same length. I even got a new Firebird drive shaft, that had this insulated balancer ring in the front. I still had some of this vibration.
I then located pinion shims and worked with the angles. This helped also but not completely. I let it go and accepted this to fact of the chacteristics of a uni-body style car. Like you mentioned, more time behind the wheel , the problem became unoticed or at least for the moment. When my kids came along, well I had more problems to worry about than a little vibration. I hope you do narrow this down.
 
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