The Stovebolt Site Forums The Shop Area Driveline Should the transmission output be centered in the frame?

I'm debugging a vibration and general noisiness in a '56 TF with a 235 and 3 speed manual. While investigating around underneath with a tape measure, I realized that the tail end centreline of the transmission is 1/2 inch closer to the drivers side frame than to the passenger side frame. The engine and differential are in the exact centre of the frame. Is the transmission also supposed to be perfectly centered? (I am of course assuming that my frame is perfectly straight). Any insights would be appreciated as this thing is just no fun above 35 mph!

Stephan

If the engine mount is in good shape and the trans mount is a stock unit and also in good shape than it's good to go.Above 35 I would get the tires balanced first and check the U joints also.

Pete

Tires were switched front to back-no difference
Tires were mounted on different rims, and balanced-no difference
Hose clamps applied to different points on the driveshaft to see if it was out of balance-no difference
Driveshaft rotated 180 degrees -no difference
Straightedge placed on driveshaft-its straight
New U-joints installed-no difference
Front wheel bearings adjusted-no difference

When I did the measuring and found the tranny tailstock to be out a bit I thought I was on to something. Well it turns out that it was only 1/4 inch out, and there is no play at all in where that transmission bolts down (unless I break out the old die grinder!)
I am starting to run out of ideas!

All the sources you checked create different types of vibrations. For instance, front wheel problems create a vibration that you can feel in the steering wheel. I take it this is not the case. I would put it up on a hoist and run it up in speed a little to see what going on.

I will try that suggestion tomorrow (but on axle stands as I don't have access to a hoist). Its tough debugging these things while driving! The truck is pleasant to drive below 30, but from that point onwards it just gets steadily worse. The vibration can be felt in the seat of my pants and in the steering wheel. By time I hit 50 its loud, and the vibration is fairly fast, and nothing makes any difference. Clutch in or out, under load or coasting, in gear or in neutral, no difference whatsoever! Hopefully the axle stand test tomorrow will shed some light on things. Thanks!

Are you running Bias Ply tires? If so, increase the air pressure a lot and see if that helps. I had the same problem with my 38, so I sold them and put radials on - smooth as silk now.

No, its already radials all around!

Bulge in tire or un round tire, motor/tranny mounts, ball joints...Sure sounds like Ujoints. Driveshaft always turns in any mode you mentioned. Driveshaft weight fell off? Rear wheel bearings? Rear end gear tooth damaged? Pinion bearing?

Tires were checked and rebalanced on different rims. Plus I figured that if one was bad I could isolate this by switching the fronts to the rear, but it made no difference at all. As for motor mounts, I'm not quite sure what to check for. I have those thin rods that hold up the front end of the engine (I've always been sceptical of that system) but the only thing I would recognize would be a broken stud (and I assume my engine leaning over on a funny angle as a result. Same for the tranny mounts. They are just giant thick rubber pads, so I'm not sure exactly what I should check for, other than properly tightened bolts which I did. As for u-joints (which I strongly suspected initially), the old ones seemed fine, no binding, clicking or slop, but I tossed in brand new ones just to be sure, and of course there's no difference. I double checked that they were properly seated as well. There is no spot that suggests a missing weight on the driveshaft. Perhaps my hose clamp test should be redone, adding some more weight to see if driveshaft balance might be the issue. That would be fairly easy to do when I run it on stands tomorrow. Plus the stand test will remove front wheels and suspension from the list of possible problems......your ideas are all appreciated!!!!

You are troubleshooting the best you can. Good common sense approach. You will probably smile when you find it. Hope it's not a big money thing. You know Ujoints need to be "phased". Lotta goofy things you can do in the name of elimination, like go down a hill with the drive shaft off. Coast with the engine off, and as you're doing, jack stands. If it still does it on jack stands, that may narrow it. If it does not do it, that doesn't mean anything except that it doesn't do it on jack stands. (considering all the things you say you have eliminated that roll on the ground tires/wheels)

so if you are going down the road and then shift in neutral ,
does it still vibrate

does it only do it at certain speed,like you can drive out of it??

We actually thought about going down a big hill with no driveshaft too!!! Hopefully we can reason it out with common sense and the process of elimination. I just don't want to use the financial process of elimination (replacing stuff that wasn't bad until I get to the thing that was bad). I despise blowing money on stuff that wasn't necessary. That money could have been blown on fun stuff!

Joker:
It starts to get noticeable at around 25 or 30 and it gets louder (sort of like fast pulsing drone) and the vibration gets faster as speed increases. By the time I'm going around 50 its loud enough to be very annoying. The vibration in the steering wheel is very fast. I have not tried going any faster for safety reasons. It makes zero difference when I shift into neutral, push in the clutch, press on the gas pedal, let go of the gas pedal, etc. It seems strictly related to the speed the truck is going, not the engine speed. I'm hoping that the ideas you guys have given me will be visible when I do the axle stand test.
It really has me perplexed!

Stephan, just went through a "similar" situation. My tires balance good, looked good but the faster I went the worst it got. Short story is I just took off 4 tires with less than 3000 miles on them and put on a new set. Problem solved. The bad tires were new 5 years ago but have set with weight on them most of the time. Strange thing is we checked the balance coming straight off the vehicle and off only 1/2 ounce....but bounced/shook/rattled like crazy. I could have had them trued up but why waste good money and cut off all the rubber.

I'm not saying its your problem but sometimes it takes a good tire man to detect this situation. My next GUESS would be take your driveshaft to a driveline shop and have them check the joint and spin balance it.

Good luck. Let us know what you find.

so, is this something new and have you been doing any work previous on the front suspension..sounds like a suspension
problem for it to shake like, take it to a good front end shop

yup,it good be tires, bent wheel also..

good luck with it and let us know when you solve the problem

I just read your posts about installing the transmission, if the truck was ok prior to that, then you know where to look..

Just went through the same issue on a 57 1/2 ton. After the wheels and tires were balanced again and the loose wheel bearings in the front were replaced, a little but not significant improvement, we were stuck with the rear end. So per my usual start with cheap and easy...yeah that was working we pulled and replaced the u-joints and..still there. Last resort? Took the drive shaft to a good shop that only does this kind of stuff. The result? The spline joint was worn badly. They took it all apart. Welded in a new one. Straightened, balanced and it is now smooth at all speeds. I did put new seals and bearings at the rear axles just so I would not have to get under this truck again for a while. The owner is happy but I wish that I had found it sooner.

This is a long shot but check the rear axles maybe one is bent.


Pete

The axle stand test has been done! Here is what we learned:
Putting the truck on axle stands and running it with the rear wheels off the ground makes no difference. The vibration and noise is still exactly the same. This eliminates the front suspension and tires as the problem. The engine has previously been eliminated as engine speed has no impact whatsoever on the noise or vibration.
Removing the rear tires/wheels makes no difference at all. This eliminates them.
Here is where it gets interesting! Our first step was to use a metal rod to feel for vibration. The rear axle and differential was very steady at every point we touched. The tailshaft housing of the transmission was not steady at all. Next we used that same rod and laid it against the spinning surfaces to see if they were spinning true.
When the rod was placed against the spinning companion flange on the differential (where the driveshaft attaches to the differential) the rod sat smoothly against the spinning flange, indicating that it was spinning true.
When the rod was placed against the spinning driveshaft however, it was a different story. The driveshaft was definitely not spinning true as the rod bounced and could not be held smooth. We tried this test at 3 points on the driveshaft, with the same results each time-the rod bounced like mad.
We also put the rod against the spinning slip yoke where the driveshaft enters the transmission tailshaft and it bounced there as well, although not as badly.
I had previously checked the fit of the slip yoke on the tailshaft and it appeared good. No wobble and it had to be lined up nice and straight in order to slide the slip yoke in, suggesting that the fit was correct. I did however note that if I grabbed the slip yoke, I could move the transmission output shaft up and down a bit. We did some measuring, and it appears that if I grab the slip yoke, I can move the output shaft up and down and the range of motion is about 0.052 inches.
Here is where I can use some advice. Is the 52 thousandths up & down play normal, or is this the source of my vibration and noise. Or is it simply a bad driveshaft. Any input here would be appreciated!

I have a 3 speed. 235, 1959 Panel. With rear wheels off the ground, in neutral, no axial play (0). Just some rotational "backlash". Did you replace the slip yoke ujoint also? I did not try moving just the main shaft with driveshaft removed. If the main shaft has .052 "runout", that would be big movement, it should be leaking fluid like crazy out the seal. That shaft seems to have a long run without bearing support. Not sure.

I assume you have not changed anything from stock, such as lifting or lowering, (changing pinion angle) etc., correct?

FROM THE WEB, NOT ME,
"Driveshaft-related vibrations usually occur at roughly engine speed in high gear. Wheel/axle vibrations usually occur at 1/3 rd engine speed or driveshaft speed because of the differential gearing. To determining whether it is the output of the transmission or the pinion in the differential, change gears when the noise occurs and maintain speed. If the vibration/noise changes in frequency, the source is in the transmission or engine. If the frequency remains the same it is a driveline problem."

Both u-joints were replaced. I can wiggle the transmission output shaft up & down about 52 thousands just by grabbing the slip yoke by hand and pushing it straight up & down with the driveshaft installed (I can do the exact same thing with the slip yoke separated from the driveshaft, but this doesn't really make any difference). I'm trying to figure out if this play is normal (I didn't see a spec in the shop manual). If the play is normal, then my issue would appear to be the driveshaft. If the play is not normal, then I either have one problem (a worn rear bearing) or two problems (a worn rear bearing caused by a bad driveshaft). I'm getting closer to solving this mystery!!!!

Just added a piece from the web

Bartamos, it looks like you were still typing when I responded! No changes to suspension, ride height, etc. No leaks, BUT I have not checked the fluid. Maybe there is none there to leak out........

Roger that, see the piece from web. As I said, mine does not move any. If drive shaft is balanced, new joints, double checked, phased, rotated 180 deg and rerun, then it is NOT the drive shaft unless it's female spline is worn... I believe it would move a little with DS removed and should be pretty tight with DS installed.

Bartamos, thanks for checking your trucks endplay. I agree with you, what I have seems excessive. I will look at either changing the bearing, or just swapping out the tranny (I may have access to a decent used one), and I will also have the DS balanced. It was a bit of a job narrowing things down, but I think we managed to do it without changing stuff that didn't need changing (OK, I did buy rims, but they were used, they were cheap, and they were way nicer than the old crappy ones I replaced, so that part was alright!). Thanks again for everyone's input, and I will do a follow up post once I have made the changes.

I would get other opinions about the radial play. It's possible it is normal. Better get more input before going hog wild.

If it is a U joint problem, the angle as loaded can make a difference. If I were putting it on stands, I would put the rear stands under the axle to load the suspension as it is on the road.

Truckernix, we did put the stands under the axle for the very reasons you mentioned. I will speak to a couple of transmission guys today to see if that end play is wildly off. Thanks!

Stephan, your main shaft and slip joint is supported in the
front by the main shaft front ball bearing and in the rear by
the bushing in the case extension. 1/16" play in the rear is
WAY to much. There should be barley perceptible play
in that bushing. The bushing is obviously worn out.
Like Bart posted with that much play the rear seal
has to be leaking badly.
That in all likelihood is where your vibration is coming from.

Denny Graham
Sandwich, IL

Success!!!!
I picked up a decent used slip yoke (mine was badly pitted and scored) and a new tailstock bushing and seal. I could not get my hands on a bushing removal tool, and I read conflicting information on pulling the tail shaft housing from the transmission, so I did it the hard way. Removing that bushing in place without the special tool is not a lot of fun. I was however able to make some hooked "grabbers" out of some flat steel bar, and after 2 fun filled hours I got it out. The new bushing was easy to install, however it took some effort to work the replacement slip yoke into place, due to the nice snug fit that the new bushing provided. There is no "wiggle" whatsoever now, and 50 miles and hour is smooth and vibration free. I also picked up the parts to replace my old, worn out tie rod and ends, so this should make 50 mph even better. Thanks again for all the help and suggestions!

Thumbs up to ya Stephan, and thanks for reporting back to us.
Good lesson for all of us.
Denny G