Vibrations at 45 MPH - advice needed

I’ve got a ‘65 Ranchero. Originally a 170 inline 6 car 3 on the tree Ranchero, I installed a 289 V8 and a Tremec T5. Other changes over the years:

Aluminum radiator, Holley Sniper EFI and Sniper electronic ignition, all new gas shocks, V8 coil springs, new shackles and bushings for ancient rear leaf springs, 3 on the tree shifting linkages removed (one steering column part swapped), after market stereo & speakers, new coil spring saddles, idler arm, new wheels and tires (still 4 lug), shoulder harnesses, alternator, voltage regulator, dual bowl brake master cylinder, new bumpers, backup lights, beefier sway bar, modified driveshaft, Doug’s tri Y headers, engine mounts, etc. It’s a manual steering Ranchero, manual brakes, power nothing and most of the underbody is as it was when the vehicle was a 6 cylinder model.

About the time I installed the sway bar and V8 coil springs I began experiencing a noticeable vibration around 45 MPH. I’ve been chasing this for years without success. I’m looking for ideas on how to sort this out. I recently swapped out the gas front shocks with Bilsteins from Open Tracker Racing in Monterey and while they helped noticeably with bump absorption the vibes remain. I just ordered a set for the rear.

Ideas:

1. It’s got something to do with the steering column as that’s where the vibrations are most noticeable. At highway speeds it’s smooth but decelerating through 45 MPH the vibrations are very noticeable.

2. Driveshaft - I had it modified for the 289 but the change to the front coil springs could have changed the length (in the vehicle) and at some speeds I could be getting a vibe from that. Not sure how to track that down.

3. Rear leaf springs - to my knowledge these are originals. The recent new shackles and bushings helped but possibly the front eye bushing/mount is badly worn and vibes come up into the frame from there. Also they could be ‘tired’ from old age causing the rear to sag and placing more weight on the rear than the front. So replacing those is an idea and I may give that a go next.

4. Sway bar - I no longer have the original but could I have done something wrong with that installation? Too much torque? Something binding? I’m tempted to remove it and drive it at 45 MPH to see what happens!

5. Rack & pinion steering conversion - would this help? I’m not unhappy with how the Ranchero steers or handles (I grew up driving vehicles like this) but I’m willing to consider options.

Any good ideas? The Ranchero didn’t have this problem when I bought it so I’ve somehow caused this along the way. I’d love to get it sorted out. My Ranchero is a daily driver and I’ve put over 40,000 miles on it. I’m close to being done but I need to get this sorted out….

 

I would suspect the driveshaft without riding in the car.
Pull it and check both u joints and look for any shiny spots on the input shaft and wear on the joint's.
While the driveshaft is out run the car up to speed and see if you still have the vibration when the engine slows down.
If no change then it isn't in the driveshaft.
After that then you will start to look elsewhere [trans clutch, throwout bearing] , I would think it would be in something you changed during the build.
Greg

 

NOT the sway bar - it cannot cause vibration. I also would suspect driveshaft, or pinion angle. Most people try to check the angle relative to the ground, which is wrong. The angle needs to be checked relative to the output shaft angle of the transmission - pinion should be pointing down at least 2 or 3 degrees. The difference can sometimes be corrected by changing the thickness of the transmission mount, or by angled "shims" placed between the rear spring perch and the spring. Also check that the output shaft is centered with the pinion, can't work correctly if it's cockeyed. And like Greg said - check the U-joints.

 

I also suspect the driveshaft, especially since you said it has been modified. I had a vibration that caused vibrations in the steering wheel and under the dash that was driving me crazy. I first thought it was a tire balance issue, but the speed of the vibration seemed faster than a rotating tire; the vibration HAD to be something spinning at a higher rpm than tires, not a tire balance issue. I decided to crawl under the car and yank on anything than spun, and ultimately I had found that one side of the front U-joint had about 1/16” slop on one side of the cross. A new U-joint fixed my issue. I also stabbed a new tail shaft seal in there too, since the old one had a minor leak, maybe from the sloppy U joint?

 

Gentlemen,

Thank you for your ideas. Initially I retained all the inline 6 steering and suspension items; I just pulled the 170 and tranny out and dropped in the 289 and Tremec T5. We measured the resulting length for the driveshaft and had it modified and balanced by Driveshaft Pros. No problems!

A couple of years later I decided the inline 6 front coil springs weren’t up to the task so I installed coil springs for the 289, but I also installed roller spring perches (from Open Tracker Racing in Monterey, CA) and a beefier sway bar up front at the same time. That’s about the time I began noticing the vibrations which only occur in a limited speed range (45 MPH +/- a few MPH).

After speaking with the guy at Driveshaft Pros this morning I suspect the U Joint angles are now incorrect or beyond appropriate tolerances. We checked them originally and they were fine, but the new V8 coil springs lifted the front of the Ranchero and of course lifted the engine as well and in so doing changed the angle of the output shaft of the T5.

So I will get it remeasured and proceed from there. For what it’s worth it looks like the driveshaft length is still okay. I’ll take a close look at the U joints while I’m under the Ranchero. I’m anxious to get this sorted.

With over 40k miles on my Ranchero I still enjoy driving it; I want to get it finished!

Regards, Jim

 

If I understand it correctly, the Open Tracker perches don't have any rubber in them, just bearings. I wonder if the lack of rubber insulation might have something to do with it? I don't see how raising the front end would change the angle of the output shaft; the engine & trans are all mounted to the frame.

 

If you have it out of gear and just sitting there do you have the vibration when you hold the rpm at 45 MPH?
Greg

 

Beer belly,

Yes, the Open Tracker roller spring perches don’t have any rubber and I recently swapped them out. While it did help somewhat the problem remains.

The engine is mounted to the integral body/frame on the inboard sides of the engine bay and is mounted in the rear on the transmission mount. Installing V8 springs raised the front of the vehicle significantly (too much in fact). I’ve since cut half a coil of each of the coil springs and while I was in there swapped back to the original style perches.

My digital angle finder arrives Tuesday; I’ll let you know what I learn but right now the transmission output angle and the pinion angles are the most likely source of this vibration.

 

My AccuMaster digital angle finder arrived. It turns out the transmission is 3 degrees down and the pinion is 2 degrees up; so that is well within tolerance. While inspecting the pinion I noticed the u-bolts securing it to the driveshaft had come slightly loose so I tightened those up. That definitely helped but my vibration problem remained.

I have already replaced the right front wheel bearings (no change noted) but now I’m going to do the left side and see if that helps.

I wish there were some way to track this down more easily. I don’t mind buying parts and fixing the Ranchero I just need to know what to fix!

 

I'm going to guess that you checked both angles while it was sitting on all 4 tires, correct? With or without a person sitting in the seat (or equivalent weight instead)?
The numbers you stated do look OK, but I'm wondering how much the pinion angle changes with you in the seat at 45 MPH? Leaf spring cars usually want anywhere from 2 to 4 degrees difference from the output shaft angle, and yours is showing only 1.
Did you happen to actually check the u-joint before you tightened the bolts? Unusual for those u-bolts to loosen unless there's bind or a bad bearing.
Just food for thought.

 

Phil,

Yes I checked the angles while it was sitting on all 4 tires (no one inside). I did not check the U joint itself other than I noted the small U-bolt could be moved slightly by hand (It shouldn’t move at all). But my vibrations could have caused that.

I did find the front left wheel had some vertical play in it. Upon removal the axle nut holding the drum to the spindle was not even finger tight! I guess I should have checked that earlier. So new bearings and cups went in and it was tightened per the FSM; that play is gone. The vibes get a little better each time I address something but they still remain.

Next up are new rear Bilsteins and new leaf springs. It may not help but they’re needed either way.

 

I should also note that I checked the angles while the Ranchero was in my garage which has a 1.2 degree slope. I don’t have a perfectly flat surface. But I had read that didn’t matter because it was the relative angles that were important.

Your comment has me wondering if I should remove the spacer block (optional) provided by Modern Driveline for the rear transmission mount. That would drop the rear of the tranny a bit and certainly change the relative angles.

 

!00% correct on the relative aspect.
That's a fairly easy test to try, although that would drop the tail, it also just may shine some light in that direction OR another. I would first drop the driveshaft and check both u-joints - process of elimination.

 

My new leaf springs arrived and the Bilsteins were already on hand so I installed those over the weekend. The passenger side front eye bolt was frozen inside the leaf. I ended up using a handheld Ryobi electric multi tool with metal cutting blade to slice through the bolt on either side of the spring eye (yet just inside the frame bracket). I couldn’t get in there with an angle grinder or Sawzall type tool.

The driver’s side bolt came right out. So now I’ve got new leaf springs, Bilsteins, shackles and bushings in back and the vibration remains.

I did check the rear U joint and there is a very small amount of play in one direction (not the other) so I just ordered a U joint press tool and will be replacing the rear U joint right away. The front one seems just fine (and was new a few years ago). I sure hope this fixes the issue!

 

For some reason the new leaf springs, shackles and bushings changed the angle of the rear differential slightly. So now I’m seeing 3.5 degrees nose up on the pinion and still seeing 2.8 degrees nose down on the tail shaft of the T5. Those should be fine but the vibration remains and now I get a little high pitched hum at roughly 50+ MPH. No roughness, just a hum. But take your foot off the throttle and slowing down through 45 MPH the vibrations remain.

 

Interesting that you see a difference in pinion angle with no change in body height? Those dimensions can't change unless the height is different or if the perch angle was changed.
Either way, that 3.5 will get worse when driving, shouldn't really be much change when coasting, though. Be sure to holler back after changing the U-joint.
One other question - does the U-joint "fit" into the yoke reasonably snug, or is there some movement? The fresh U-joint would be the one to check with.

 

Google "drivetrain vibration when decelerating", and you'll find that it's almost always U joints or driveshaft balance.

 

One other thing you can check, look at your driveshaft and see if a balance weight has come off.
Greg

 

I think the factory original springs were simply worn out and mounting new leaf springs on changed the angle at which the rear axle sits in relation to the vehicle. I was took my time and was pretty meticulous with the spring installation making sure the spring and axle were well seated to one another while tightening up to torque spec per the FSM.

The rear U joint was definitely having problems - when my press tool arrives (hopefully today) and I can finish getting the old joint out and begin trying to find a replacement. I have the PDF Ford Parts Catalog and the U Joint part numbers for my vehicle (65 Ranchero) show either a C5DZ-4635-A (or -B) part with a width and length that is longer than the unit installed in my Ranchero! Mine is closer in size to a C3DZ-4365-A but it’s hard to get really accurate measurements with the spider still partially installed on the driveshaft. It’s weird though that my ‘65 would have such a different spider than the parts book spec. ??

 

You say you're still using 4 lug wheels, so are you still using the original 7-1/4" six cylinder rear axle? The C3 U joint sounds like it's a six cylinder part number, and might not be up to the task of handling the 289's output. If that's the case, I'd bet you'll find a brinelled U joint.