Vibrations at 45 MPH - advice needed

Yes, I’m still using the inline six axle, brakes, etc. I only changed the fewest components when putting in the 289.

Engine mounts, headers, exhaust, transmission (Tremec T5 floor shift), Z bar, etc. The driveshaft was shortened and balanced by Driveshaft Pros in Ventura, CA. The forward u Joint was new and came with the yoke for the T5.

The rear U joint - to my knowledge - is original and unmolested. When I first looked at it a few weeks ago (?) the u bolts mounting it to the pinion flange were loose on one side. Whether that was a symptom or was caused by the joint issue is unknown. My U Joint press tool arrived last night so I’ll get it out this morning and head to the auto parts store.

I suspect trying to swap to a larger U joint would require some effort (finding a larger compatible flange, then modifying the rear mount on the driveshaft, etc.

I’m inclined to try the same part first and see how that goes. Eventually I may be forced to find a Ranchero V8 rear axle - at least at this point I know I can swap the rear end out easily enough in my garage.

I’m willing to spend some money and get this solved if necessary. After 40,000+ miles on the Ranchero I still enjoy driving it in spite of the limitations of vehicles built in that era. The Ranchero doesn’t owe me anything - I enjoy working on it. If I were to start all over again the only change I’d make is to start with a V8 Ranchero instead of a 170 inline six model.

 

The U joint is out; its dimensions do not match any of those listed in the parts catalog. Perhaps I’m using that improperly! Ordered a new one at the auto parts store based on dimensions. For what it’s worth CJ Pony Parts appears to have the exact same part shown as appropriate for a 65 Mustang with a 170 six. In any case my bearing was chucking grease so I know it was bad. Hopefully this will solve the drivetrain vibrations as well. Worst case scenario I may be looking for a V8 rear end.

 

The rear axle is a WCY-F model, 7.25” ring gear, conventional, 3.50 ratio. If I need to get a beefier rear axle what is recommended? I see in the FSM that various axles exist with ring gear diameters in either 8” or 8.75”. I know where I can get something I just don’t know which one I might want…

 

Got the press in, pushed the U Joint out first one way then the other. No problems. It moved easily once enough once it started moving. C clip removal was easy as was unbolting the u bolt retainers from the rear flange.

Ordered one from the auto parts store and picked it up Monday. Installation was pretty simple *except* I was able to press the caps into the rear of the driveshaft by hand (some pressure required but no tool). That seemed odd but after installing it I could detect no play in the u joint. There is a trick to the C clips - get the unit installed in the driveshaft first then tap those 2 in with a hammer, then immediately 2 the other 2 into the end which mounts to the pinion with a hammer because once it’s installed on the pinion you can’t get at them. Worked like a charm.

First local test ride no noticeable drive train vibrations between 40 and 50 so I took it out on the freeway for a high speed run which is when the problems began. Long story short made it home but getting a noticeable and uncomfortable ‘clunk’ every 50 - 100 yards while moving. Limped home, crawled under it and everything looks good and tight.

Called the guys at Driveshaft Pros in Ventura and they said aftermarket U joints (like my Moog) are intentionally undersized around 2 thousandths to make it easier for home mechanics (like me) to install them and he feels that’s the problem (especially since I pushed them in by hand). So next week I’m going to pull the driveshaft and take it down to them and get it professionally sorted out….

The saga continues! I’m not disappointed at all, I put in a good effort on this without spending much money. I’m hopeful I’ll have a solution soon!

 

Jim, I'm no expert, but there may be more going on than U joints; your differential maybe be giving up the ghost behind that 289.
Here's the original factory I.D. tag on my 289 4 speed Ranchero; it's a 2.80 non-locking differential:



And here's a decoder for identifying Ford differentials. According to this chart, my WCZ-E has a 7-3/4" ring gear, but most folks just call it an 8 inch. You can see the smaller 7-1/4" diffs listed here too:
https://www.fordification.com/tech/rearends_ford02.htm

 

I'd say that you probably are in the right place - the work affected the vibration, albeit temporarily. Before you remove it, put it up on jack stands (under the rear end housing) and run it in gear and visually check the driveshaft to see if it "hops" or what it actually does when it's clunking.

 

Removed the driveshaft and took it to Driveshaft Pros in Ventura (they did the original shortening, rebalancing and T5 yoke installation for me). They inspected my Moog U-joint installation and pronounced it “good to go”. After discussing my yoke, pinion and driveshaft angles they recommended I install 1 degree shims to lower the pinion angle.

Ordered some from Summit and installed them pretty easily yesterday morning. Went for a test drive and the deceleration vibrations are gone! Major improvement. I’m not sure I’m finished with this as I am noticing some hesitations while accelerating gently. I’m going to remeasure the angles now that the shims are installed and I’m going to check for drum brake drag which could be a source of the hesitation sensation.

Ultimately I may have to see a professional to get this sorted but I’m making progress…

 

Glad to hear the shake is gone, now go find somebody that's proficient in tuning Sniper EFI - even though it's "self learning" a good tuner can make it drive the way it should.
Brake drag will not cause a hesitation, just makes it work harder.
Please report back with your new angle findings.

 

I spoke too soon! The shakes returned with a vengeance this morning on a short local drive. I have not yet had a chance to crawl under the Ranchero to see what’s going on.

At the very least we have identified the problem, which is the first step in getting it fixed. Stay tuned…..

 

This has been quite an adventure! My ‘65 Ranchero was fine until I installed the 289 and T5. We had the driveshaft shortened and rebalanced at that time, swapped out engine mounts and the tranny mount but the rest was stock 6 cylinder stuff.

Initially it rode reasonably although I’d get some minor vibrations when decelerating through 45 MPH. 18 months or so later I added V8 coil springs up front which significantly raised the front of the vehicle and the vibrations got progressively worse. Then I added Bilstein shocks which really helped on noticeable road bumps but not with the vibes.

So I replaced the rear shackles and bushings (mine were shot) but no real change. So I ordered new leaf springs for the rear end to replace the saggy originals and things got worse so now I had to get it sorted for the vehicle to be driveable.

Somewhere along the way the shaking had caused the u-bolts holding the rear U joint in place; I tightened those which helped a little but the U Joint was clearly shot so I replaced that but the vibes persisted.

I bought a digital angle finder but it’s hard to get good readings under the vehicle (not much room) on a driveway that isn’t level.

I ended up ordering some 1 degree shims from Summit Racing and put those in the way the suggested way and things got worse. After more measurements I decided to reverse them and suddenly things got a lot better.

I also played around with shimming the T5 mount up various levels. Right now I’m seeing 3.8 degrees down at the tranny and 3.2 degrees up at the pinion and it seems to be working pretty good.

While working on the rear end I was checking everything and found a leaky rear brake cylinder which was a separate adventure and that has been fixed. It’s a 3 handed job and I only have 2 but I got it done.

I also checked the right rear wheel for play in the axle bearings and I believe I have found some as I can wiggle it slightly up/down and fore/aft with it jacked up. I’m still getting a very small high speed (but small) vibration in the package tray while driving which still could be the U joint but it also may be axle bearings which I suspect are beyond my ability to swap out at home.

Anyway it’s driving better than it has for years and I may start looking for an 8 inch rear end. I also pulled the driveshaft and had it rebalanced and that was perhaps the final difference maker in smoothing things out.

I have not checked the left rear for axle play but I will. Then I’ll need to come up with a plan to either pull and replace the axle bearings or swap to a more robust rear end.

 

Glad to hear progress is being made. Personally, I think the 8 inch rear would be a wise choice, (especially with a manual trans), since that's what Ford did behind the 289. Then you get involved with a slippery slope- 8 inch uses 5 lug axles, so you'd be faced with 4 lugs front and 5 lug rears, and non-matching wheels. Steel wheels with hubcaps would conceal that. Or would now be the time to upgrade to V8 front suspension, disc brakes, etc? You made it go faster, but will it stop faster? I hope you get it sorted, because you have a great looking Ranchero, and it should be driven safely, and a lot.