TKO 600, mcLeod Street twin diphragm clutch behind 440 in 68 Charger:
The car has a vibration in 4th gear. Other gears are fine. It is not too bad but something is not right - the vibration can be felt through the steering wheel and the shifter and also creates a low drone inside the car. Strange thing is that even though it is still there after miles of driving/warming up it goes away after a couple of short burnouts!!: Warm engine after 20 miles driving and it vibrates - then if I do a 10 sec burnout in 1th gear it is smooth as silk! What is going on? It has been like this since I first installed the driveline years ago. I had the trans apart for a check. Axle end play checked in good between tolerance limits. My first idea was too much end play for the lower axle in the trans as the vibration only comes in in 4th gear direct drive through main axle. Any ideas?
Trans has always shifted a little slow/hard, has upgraded syncros with carbon lining and has been run with both ATF and Syncromesh without much difference. Bellhousing is well dialed in and cluch/flywheel are balanced.

Sounds like a fun one to track down.

Are you sure it's not a resonance from the engine or exhaust that is only present at a particular speed and load?

Could it be the driveline balance or angle?

Have you put it on stands and tried it with the wheels off the ground? If not, try it. If it is still there, pull the wheels and try it again. Be sure to secure the rear brake drums/rotors with lug nuts first.

What's the drive line angle in degrees vs the pinion angle in degrees using an inclination meter?, what mfg's driveshaft are you using?


Shifter "buzzsaw" vibration is quite common on early TKO 500/600 transmissions, most of the current mfgs/TKO kits offer revised later generation shifting base mechanisms to eliminate the buzzsaw effect sometimes experienced at certain rpm/throttle conditions

Mike

Had the same issue on my Chevelle for years. Tried everything with the muncie setup,drive shaft,pinion angle ect. Finially did the TKO 600 conversion and it was still there. Ditched the poly trans mount and went with the OEM from NAPA IIRC and problem is GONE. It was a resonence type drone with a shifter buzz that I could regulate with the throttle at about 55-65 mph. If you have a Poly mount give it a try.

I now run Keislers new shifter and there is no buzzing noise coming from there. The vibration can be felt through the shifter handle thou.
I chased a different vibration earlier and by that went through multiple pinion angle checks (3 degrees nose down - XHD springs), car up on jack stands, bell housing indexing, drive shaft check etc and found that the clutch and flywheel was not balanced correct. After balancing all was fine except the vibration in 4th gear.

I have tried running at same speeds, rpm's etc in other gears but can't get the vibration in other than 4th gear.

Every piece in brakes, wheels, suspension, steering and driveline were new or rebuilt a few years back and only have like 6-8K miles on it.

I do run a poly trans mount like the ones Keisler used to supply and would like to try a rubber mount if I could find one that fits (it is the thick pad placed between the trans and the trans cross member - not a stock looking thing). Any idea where to find one? I guess that would make for an overall smoother ride. Still I think I am overlooking something as the 4th gear vibration smooths out after a couple of burnouts.

Like I said the trans shifts a little slow/hard without any grinding. Not sure but I have a feeling that it shifts better after some abuse when the vibration is gone. Anything related to tolerances and heat?

The Keisler kit uses the Ford transmission mount in poly, listed below from Summit Racing (perhaps your best vendor seeing your in Norway, and shipping/customs can be an issue)bolt pattern is all the same, only difference between the two, is the height you may require...both models are rubber OEM

What fluid are you running?

Mike

Thanks for the links! Great! AT what power level do you think the rubber mounts start being an issue (when running slicks)? I run Syncromesh - or more correct- Quaker States version of it. Actually I think I heard that ATF will work better with the carbon lined syncros. Climate here is quite cold compared to yours and that might also point in the direction of running ATF. I ran ATF prior to the syncro upgrade. >Same issues then.

i'm glad you posted this, as i was thinking [now proved wrongly !] it was a gm mount for something like a pg, T350, etc. as most of those have a 3 bolt bottom mounting pattern and are not very tall. that mount is used on a ton of GM vehicles for years and years, and i just thought that would be used because of being widely available world wide. shows how much i know.

Not the real issue I guess but it is time to try a rubber trans mount anyways. Any ide of what height the two different Ford rubber mounts are?
Summit doesn't list any height.
The poly mount I have is about 2 1/2" high but is shimmed another 1/3".

The 2784 is the Mustang mount which was used in most of the early Keisler kits, it's the taller of the two, plus it's a Tremec application for the Ford Mustang, depending on your driveline angle, you may still need to add a shim to increase the height

Thanks Dayclona! Still hoping for more ideas around the vibration.

Still curious as to what your driveline/transmission angle is in relation to the pinion angle, you stated 3 degrees down?, is this in relation to the driveshaft or transmission?


Also who's driveshaft are running, Keisler supplied?, if so when (year) was it purchased?


Mike

Pinion 3 degrees nose down in relation to the trans. Can,t recall the position in relation to the drive shaft. Driveshaft is custom made at a professional machine shop. Originally it was made for a shorter joke and was shortened an rebalanced (by the same shop). Vibration always was the same.

3 degrees down from the trans is OK, driveshaft angle should be 1.5 degrees ideally , no less than 1 degree, and no more than 2-3 degree deflection to the pinion or transmission angle, do you know what speed (RPM) the shaft was balanced too?, as most driveshaft shops only balance to 3500 RPM on average, Keisler did this also in the early stages of production, then around 2004/5 they started balancing to 10,000 RPM to better control the harmonics the shaft would see thru out it's RPM range

I do not know what speed the drive shaft was balanced at. The strange thing is that the vibration is gone and the shifting goes smoother and faster after some abuse. Never been happy with the way the trans shifts either. I have gone through bellhousing alignment, clutch release checking etc. several times to no change. The slightly slow shifting might be related to the twin disc clutch maybe? It is some weight in there compared to a single disc. Any experience?

Finally got time to get under the car to swap in a rubber transmission mount (no test drive yet as this is not the real problem). I noticed that the front yoke has some play. Pushing the yoke up/down or sideways displays a good visible movement of the yoke against the trans rear seal. How much play is acceptable for the yoke and how would you meassure it?

Just want to update: The rubber transmission mount took car of most of the vibrations but I can still feel a slight vibration in 4th gear an as before it goes away after hammering on it for a little while.

Update: Finally got time to work on the car. Installed an air/fuel gauge and got some weird readings. Checked the carburetor, Edelbrock 800 AVS, and found that the drivers side metering rod was not sliding free in the bore/jet. It would actually stick in the upper position! Seemes like the spring-like part that attaches the rod to the piston was bending the rod too hard to the side. Quick fix and guess what!: The vibration is gone!
This issue made the motor vibrate a little and also caused the low end to be a little touchy impacting shifting feel. It seems to me that stepping on it would free the rod by causing an instant vacuumn change when letting off the throttle. I am quite shocked that this little issue would cause all kind of weird stuff! Guess who is happy!

Glad to hear your issues got resolved!

Mike