Great responses and now I have more pointed questions. Thank you very much for the help and support. New to these newsgroups so if this post more than once I apologize in advance.
I know that the garage marked and connected properly (as original) the
2-piece driveshaft in the middle where the rear part meets with the front, but does it also need to be connected as it was originally where the rear driveshaft meets/bolts to the rear differential??
2)Is there a way to know how it was originally connected
3) why does it only vibrate between 55-60 for the most part
4) How can I confirm the off-center for thedrive flanges at the differential is normal, looking at the rear shaft from underneath, I know it will slant down from the center connection between front/rear driveshaft, but the rear driveshaft also tilts to the left or right and not inline with the front shaft.
Appreciate your help.
"
jpan wrote:
> > I have an 88 toyota 2wd pickup long box with a 2 piece drive shaft.
> > I got the rear and mid/intermediate ujoints replaced by a garage.
> > Since then, I get a vibration from the rear end especially between
> > 55 and 60 km per hour whether I accelerate and with my foot off the
> > gas. We balanced the tires but I still get the vibration.
> >
> > I know the garage marked the connection where the rear axle and
> > front (it is actually called intermediate axle) meet, but not sure
> > if they marked where the rear part of the axle meets with the rear
> > differential (remember it is a 2-piece shaft). Anyway, I took a look
> > at the length of the 2 piece shaft and the rear part of the 2-piece
> > shaft is not in line with the front part. It goes off to an angle
> > from the midpoint join as it connects to the rear differential. > >
> > I know it matters that the rear and front/intermediate diff meet in
> > the middle the same way they were disconnected, not sure if it
> > matters if the rear diff joins in the same position with the rear
> > axle. Anyway, is it possible the garage connected the rear axle to
> > the rear diff in an incorrect manner causing (different than how it
> > was originally connected) it to be on an angle or different angle
> > than originally and thus putting a strain on the ujoints, hence
> > vibration. Or am I way off here.
"Giancarlo Pagliaroli" wrote in message news: snipped-for-privacy@look.ca...
AFAIK, it does not. The driveshaft is balanced so that it does not vibrate when spinning. The differential is balanced internally, independent of the driveshaft. So it shouldn't make any difference when mating the driveshaft to the differential. Logically, if it DID make a difference (i.e., if the driveshaft and differential were balanced together) then it would be impossible to replace one or the other without having the entire assembly rebalanced.
There are two ways to look at this question: 1) How should the parts be connected? For that, refer to the Factory Service Manual. 2) How were the parts actually connected before? Unless you have photos (or you inspected the parts before and you have a really good memory) then you'll probably never know. You may be able to see mating imprints in the dirt, grease, rust, scratches, etc., between two parts, but it's unlikely that you'll be able to reverse the assembly process based on that alone.
That's called "harmonics." I don't want to get into a long physics discussion, so I'll try to keep this brief (and somewhat simplistic). Everything on your vehicle vibrates while in motion. The goal of balancing and isolating a part is to minimize the vibration (and keep it out of it's natural harmonics) so that the vibrations are dampened, and thus not noticeable. However, if a part vibrates at the same frequency as one of it's natural harmonics, then the vibrations will amplify. Think of your driveshaft as a guitar string. Based on the material of the string, the thickness of the string, the tension of the string, and the length of the string, that guitar string will naturally vibrate at a particular fundamental frequency (thus producing, hopefully, a pleasing sound). If you were to induce a vibration in the string that is NOT a multiple of that fundamental frequency, then those vibrations will naturally dampen (i.e., die out). However, if you induce a vibration that IS a multiple of that fundamental frequency, the vibrations will amplify until they reach a maximum. In the case of your guitar, the string will produce sound. In the case of your driveshaft, it will produce a very noticeable vibration. So, based on the material of your driveshaft, the physical shape of your driveshaft, the length of your driveshaft, etc., combined with an out-of-balance situation, your driveshaft has a natural harmonic frequency at the rotational speed which drives your car at 55-60 mph. Above or below that speed range, the frequency of vibration induced by the out-of-balance, does not match the fundamental frequency (or one of it's multiples) of the driveshaft. But it is vibrating at all speeds, it's just not making "music" outside of 55-60 mph.
Uh, something's not right here. I've never heard of a main driveshaft that's not parallel to the longitudinal axis of the vehicle. Even if a vehicle were designed such that the output from the transmission was not horizontally in-line with the input to the differential, the driveshaft would always be angled to one side (i.e., always to the left or always to the right, but never "tilting to the left or right", which would be an off-center driveshaft condition).
If your shaft IS off center, that would mean that the shaft is improperly assembled so that it's not co-axial at some point. Either it's not centered where mated to the differential (but if so, I doubt it could be so far off that it would be noticeable to the naked eye), or one of the u-joints is incorrectly assembled so that one segment of the driveshaft is displaced off to one side.
Have you tried grabbing the driveshaft and seeing if it has any play in it? (Btw, I do NOT recommend trying that while the engine is running!) Shut everything off, and for safety, disconnect the battery ground (negative terminal). On level ground, chock both the front wheels and place the rear axel on solid jack stands so that the driven wheels are not in contact with the ground. Then put the transmission in neutral and release the parking brake. That should allow you to freely rotate the driveshaft by hand. Move along the driveshaft with your hands, grabbing it with one hand on each side of an interface (mounting flange or u-joint) and see if you can wiggle it. If you find play, then you've found your problem. Also, check to make sure that each u-joint is centered and has all the correct parts in place: bearing cups, circlips, etc. Finally, check to make sure that the bolted connections have all the bolts, washers, and nuts in place. Everything should be symmetrical.
Also, inspect the driveshaft 360 degrees around along its entire length to see if there is any damage (e.g., dents) or missing balance weights. Balance weights are little rectangular pieces of metal that are normally spot welded on to the shaft. So if one is missing, you should be able to see the broken weld spots (and/or an outline from where the weight used to be).
The only other thing I can think to check is if your driveshaft has a center support bearing. If so, make sure it's smooth and properly supported. Often the center support bearing is "floated" in a ring of rubber and the rubber can get old and crack or tear.
No. Unless it was marked before it was taken apart.
That is the speed at which the out of balance occurs. Same as a tire that is out of balance. It will vibrate at a certain speed but will not vibrate at a faster or slower speed. I would look to see if maybe the balance weights were knocked off the driveshaft when the ujoints were replaced.
Unless someone moved your rear axle to one side it would be normal. If the rear axle were moved one tire would be further under the body while the opposite tire would be sticking out past the body.
I would suggest you take it back to the shop who did the work and have them figure it out. If it didn't vibrate before the ujoints were changed it shouldn't vibrate after. They should fix it for free if it is something they caused. If they are unable to figure it out you should not have taken it there in the first place. If that is the case take it to someone who knows what they are doing.
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