Technical T5 Swap Vibration Woes

I have seen this on early Falcons, and not just a few times.

It has almost always been when the under-engine brace is missing. When it's not, it is because the car has been hit in the nose.

That brace keeps the very thin front subframe rails from twisting, and keeps the engine mounts aligned.

Leaving it out will allow shift, and especially on a 1960-1961.1 chassis, cracks.

It only takes a couple of degrees, on any plane, that are not matched by a matching change at the other end, to create driveline vibration.

Angles can be sharper than most would consider acceptable, but if they don't exactly match at both ends of the driveshaft vibration WILL occur.

Engines, transmissions, and pinions can be offset, but they absolutely must be parallel with the chassis centerline, when viewed from above.

 

Also, there is this:

Both of these are listed as the correct engine mount:



The Anchor brand one on the right is arbitrarily 3/8" shorter.

This alone WILL create vibrations.

 

Most drive line manufacturers state that a 3 degree working angle is the maximum recommended operating angle. More than 3 degrees and you can get torsional vibrations so this is something else you may want to look at.

 

Are you using Automatic transmission fluid in your T5 Transmission? It was designed to run it not Transmission Oil.

 

I think you should change rear axle angle and test it since it was changed too

 

This car was hit on the nose. I had to take it to a frame shop and have the subframe pulled back straight. The floor is pretty crumpled and I had to section in a new kick panel. The front brace is in place under the engine.

I can string the engine/trans front to back and try and correct the slight shift in the trans to the pass side and get it straighter in the chassis.

Both engine mounts were replaced at the same time the trans was originally installed. Both with the aftermarket weststar mounts.

Yeah it’s running ATF.

I was considering this, unfortunately the yoke on the 8” is a 1310 and the original 6.75 rear uses a much smaller u joint. I’d need to have yet another driveshaft made to toss the old one in.

Yeah I’m definitely exceeding that at 4 degrees. More on the front u joint with the engine angle.

What techniques have you all employed to correct this? Seems like my best bet is to raise the ride height.

 

Good thought. I was thinking I’ll get it back up on ramps and get a video. Maybe do one of those slow motion ones to see if I can observe anything.

I have a junkyard driveshaft out of a crew cab Maverick that doesn’t seem to suffer quite as badly from the high frequency vibes but it definitely lobes more.

Thanks Marcus, I appreciate the insight. This is a good next step I think and a good plan. Get as much right as possible by the book.

Any idea on how to reduce working angle without raising ride height?

I had one of those on the 8.8 I swapped in my 50 chev. Didn’t see one on this mav rear when I pulled it, but it’s possibly some may have come with it.

Likely the trans mount, could be other things. The generic t5 swap/ c4 mount didn’t clear my floor very well so I had to hack it apart a few times to get things in a happy spot.

Where did those wedge shims mount?

 

In the 80's Ford hung a mass damper off the front of 7.5" diffs in Fairmonts/Zephyrs. These cars were mostly peashooter/AT cars. Earlier 78/79 V8s did not have them. Later the 8.8" Mustangs did have them as well. Lovingly referred to as 'Moose Balls'.


Mass damper bolts though from the bottom of diff, there are two flanges/wings on the 7.5/8.8, upside down U bracket also acts as a contact pad for the body mounted pinion snubber.

I recall a similiar device on a '75 Granada Ghia 4dr(351/C4/8.7" weirdness).

If the ride height is what you want, and rotating the axle housing is not an option, then changing the powertrain angle to work is your next solution.
Currently working out the angles on a friends OT to fit a swap.
Don't forget to walk away from time to time and come back to it if your getting cross eyed.
We had good angles but my bud was getting hung up on *something* walked away for a couple hours, angles were good, clearance was good, but hanging upside down under a car can sometimes screw with your perspective.

Using factory mounts is preferred as the engineers have the required mass and durometer for nvh worked out, just takes a bit of fabrication and finagling to get it goldie locks.

 

If both your engine angle (down) and pinion angle (up) are at 3 degrees and you are getting 4 degrees working angle then you need to evenly lower the engine to reduce the working angle if the drive line angles down from front to rear. Another potential problem is if you have leaf springs because you want the pinion angle to be about 1/2 a degree less than the engine/trans angle to compensate for spring wrap/pinion rise on acceleration.

 

I would get the shaft balanced/checked for straightness first. As advised look at the mounts carefully. I've seen some look good, but fell apart when taken out.

 

I don't remember anyone saying both front and rear joints need to be at the same angle

 

It was common practice on many leaf sprung cars to run with the pinion angle down a degree or so to compensate for spring wrap-up BITD ...seemed to go down the road just fine . Many vehicles were produced with weights hanging off the back of tail shafts & off the nose of the pinion , some had "inertia rings " built into front pinion yokes , some on trans yokes . No particular help but driveline vibration is a common problem .

 

I was just going to type the above! Rotate the rear axle 3° down from currant position and see what happens.

 

Shims went between spring pad on rear end and spring in front or behind center bolt.

 

Ask your driveline builder about a Double Cardan joint.

 

Because you have stated that with the driveshaft removed there is no vibration, that removes incorrect engine balance, bent shaft in trans and probably bad engine mounts. After 3 driveshafts, the shaft itself is probably not the cause. My vote is for alignment. I would try a cv joint at the trans yoke on my shaft. I think there is a valid reason why so many new cars have them. Everytime I have run into a similar situation, it has been the rear end was off set some and we had multiple angles to deal with. Some people are lucky and don't have vibration but many do. A driveshaft expert can tell you the capabilities in misalignment of a cv joint. Good luck with the chase. It sounds to me like you're very determined already.

 

Eh doesn't necessarily remove engine balance. I've seen some engine balance issues only show up under load

 

Did you check the flex plate, flywheel to see if you have and problem with it. We had a Pickup the had a vibration and it was a bad flex plate. Just my two cents. Good Luck

 

I did.

 

Absolutely not necessary.

This specific combination is a proven one, without resorting to extreme measures.

 

There have been previous threads on this site tied to pinion angle. I was surprised to find that there was some confusion regarding how pinion angle is viewed. If the trans is 3 degrees down, I (me personally) locate my pinion 3 degrees up by putting a jack under the pinion/yoke and RAISE IT but, some people claimed that my "up" is actually down as THEY see it. They view an imaginary line (as viewed from the side of the car) through the engine/trans and see it running downhill from front to back. They then draw a line through the pinion (again, front to back) and see that too running downhill front to back so they claim "engine/trans down 3 degrees, pinion down 3 degrees". Although we, in the case outlined above, are coming up with the same thing, just wording it differently, I am not entirely clear on how YOU are measuring your angles. Is it possible your imaginary line through the crank/trans is running down but your pinion gear/shaft is actually running UP front to rear, when viewed from the side?

 

A cross and roller U joint at an angle does not transfer speed evenly when it is at an angle driven half will speed and slow down with every revolution but if the joints are in plane and angle is the same the second joint will cancel out the first .

 

Another thought...Back in 2014, here at the GM dealer we had 100's of new trucks with drive line vibration. Long story short the cure was to replace ring and pinion gears. Somehow they were not machined correctly. Google GM truck vibration for better info.

 

Ford had the same problem in the late 70’s. Usually the ring gear had excessive runout. It was a big problem!

 

I recall ours had variation in the backlash, every other ring gear tooth had to be measured and compared.

 

I remember mid 60's fords also had a balance weight on the trans tailshaft. One time I left it off, and it sure did have an effect.

https://secure.cougarpartscatalog.c...ation-Damper-C4-Used-1968-Mercury-Cougar.html

 

Pinion angle needs to be adjusted slightly for axle wrap and vehicle loading however you want your driveshaft to be as near perfect as can be in normal driving
Dan

 

Up on one end, down on the other. Up on both ends. Down on both ends. All are acceptable configurations for eliminating the vibration induced into the driveshaft caused as a u-joint rotates.

@Sharpone the fourth example in your image is acceptable.

If the angles at each end are equal, then the vibration caused at the propelling end of the driveshaft is cancelled by the u-joint at the propelled end. And it's not actually a vibration, but perceived as one due to the fact that the driveshaft speeds up and slows down twice per revolution due to the angle of the joint. I think by now we've all seen the video made years ago by Spicer or some other drivetrain company showing this phenomena. If not, the video is at the bottom of my post.

A "W" driveshaft configuration, while not normally practical, has identical capabilities to eliminate this "vibration" as a traditional "Z" configuration as long as the angles are equal.

 

Sort of ... maybe ... ish.

Engine trans 3 degrees down. Pinion nose raised to match the 3 degrees ... all is good.
Now, take that SAME car and instead of swinging the nose of the pinion up, swing it down until you get to the "other" 3 degrees. I won't argue that they won't continue to cancel each other out BUT what have you just done to the angle of the U-joints? They are definitely not staying the same.

 

In 1962 I put a Fairlane 221 and 3 speed in 60 falcon and had the same issue except it only happened in deceleration push the clutch in and it stopped . It was the trans mount.