Possible Ford 9" vibration at 65 to 70mph

Discussion in 'Axles / Suspension / Tires' started by Tim C, Jan 30, 2019.

  1. Tim C

    Tim C Wizard

    Joined:
    Jan 22, 2007
    Location:
    Fayetteville
    This isnt on my 4x4 but I figured I'd post up to see if @Jody Treadway or any of the ECGS guys may have seen this. Its on my 67 Ford Fairlane. I've got a vibration/ resonance that starts up around 65 mph and goes away just after 70 mph. It will do this even if you clutch in so the engine rpm drops to idle. It will start making a sound like tsl boggers on pavement at the same time but the frequency and volume of the bogger noise will change even at a steady road speed. Pretty sure its coming from the rear axle area. Read on for more info if you're intrested. LOL

    Now for the long story: Unfortunately the car is basically brand new so I can't narrow this down to any particular factor. I'm turning this thing into a cruiser from a drag car. Last year before the hot rod power tour I pulled the drag springs out in the front and lowered the car several inches. I built a new 445 stroker engine last year (390 FE stroked to 4.25") with a roller cam. Pulled the old 390 just after Thanksgiving and got the new one dropped in and running just before Christmas. Only put 60 miles on it. The new engine idles smooth for the cam it has and it revs smooth in neutral. Pretty sure its not the engine.

    While doing the motor swap, I removed the old collapsed stock eng/trans mounts that had been welded solid with plate around the rubber and replaced with stock motor mounts because the solid mounts made the whole car shake like crazy. The new mounts had the engine and trans sitting higher in the frame (the trans is now closer to the tunnel under the car for example). Because of this my previous slight driveline vibration got much worse. Before it would shake at high speed and get really bad on decel. After the motor swap it got a terrible vibration on acceleration. I narrowed that down to the pinion angle, basically trans output was 2* down, driveshaft 3* down, pinion 2* down so the angles were mismatched and it was "jump roping". Basically 1* on the front joint, 5* at the rear.

    To better measure the pinion angle, I pulled the driveshaft at work one day on the drive on alignment lift. On the way home the vibes were much worse and I started smelling gear oil burning. By the time I got home the yoke had welded itself to the output on the trans. I had to beat the driveshaft out of the trans with a 3 lb hammer. The output shaft was blue from the heat. When I put the shaft back in at work it pushed the tailhousing bushing into the transmission so there was no support and the shitty pinion angles let it beat itself to death. Obviously it was on its way out already. I ordered a new 31 spline output for the toploader 4 speed, a new tail housing with bushing, and a rebuild kit and rebuilt my toploader. I also ordered a new aluminum balanced driveshaft from a company out of Texas that a local buddy with a coyote swapped 68 F100 uses for his own trucks as well as customers.

    I removed the old homemade unadjustable ladder bars from the car along with the housing floater and put perches back on the 9" after I set the pinion angle at ride height so now the trans is down 2*, axle up 2* so the angles are the same and pointing at one another now with the center lines parallel like they should be. 1* at each end. Made a set of custom traction bars that bolt in where the ladder bars used to be to keep axle hop down.

    The car accelerates smooth now all the way up to 90ish so the driveshaft and angles should be good now. I had thought it may be in the tires and the nittos were at the wear bars so today I put a set of P275/60R15 (28x10.5) cooper cobras on the weld draglite wheels and balanced them at work. They run true on the hunter balancer and balanced out well but the vibe is still there. I also swapped the driveshaft 180 degrees at the rear pinion yoke with no change.

    I also got a set of 3.70 Richmond gears and a TruTrac for Christmas to replace the 4.11 and spool. Im no expert at setting up gears but I used a pinion depth checker and adjusted from there about .005 to get the pattern looking good. I do have a slight gear whine at 55 to 60 but I can live with that its barely noticable over the exhaust. The car has 35 spline moser axles and special (expensive) axle bearing since it still uses the small housing ends. I had to buy two bearings after the power tour because the races had cracked and were leaking oil. Supposedly they do that with street driving because the races are so thin. I plan on getting the big bearing ends welded on but I was hoping to wait a little while until the credit card stopped smoking after all the above.

    tl;dr

    Motor new, Trans new, driveshaft new, rear axle new, tires new vibration at 65/70mph

    I dont know whether this particular vibe has always been there or not because the solid mounts and jacked up pinion angles have caused the car to always vibrate since I've owned it. Now that everything else is running smooth, it is very noticable. Im hoping to do the power tour again this year so I'd like to get this figured out since it is right at freeway speeds.
     
  2. Jody Treadway

    Jody Treadway Croc wearing fool Moderator

    Joined:
    Mar 20, 2005
    Location:
    Hendersonville, NC
    Sounds like the pinion needs to be rotated down a couple degrees so that under power (when it naturally raises) it will be in proper line.

    Usually about 2* down from the transmission.
     
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  3. Tim C

    Tim C Wizard

    Joined:
    Jan 22, 2007
    Location:
    Fayetteville
    Well I can get a set of leaf spring wedge shims to try rotating it down a few degrees but I figured since it does this at cruise and I didn't notice a vibe on acceleration it would be ok. Under power it blasts through the 65 to 70 mph range so quick you don't have time to notice any vibration, lol.
     
  4. Jody Treadway

    Jody Treadway Croc wearing fool Moderator

    Joined:
    Mar 20, 2005
    Location:
    Hendersonville, NC
    Most of the time, a specific speed related resonance like that will be directly related to driveline angle and/or gear setup. Driveline balance, wheel balance, etc will yield itself across a broader range.
    Too shallow a pattern will cause noise like that. But from your description (unless I'm picturing it wrong) it sounds like the pinion is too high.
     
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  5. a_kelley

    a_kelley mister mechanical fixer

    Joined:
    Jan 26, 2010
    Location:
    Rutherfordton
    Could also be the pinion is rotating up under the torque under hard accel...
     
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  6. Tim C

    Tim C Wizard

    Joined:
    Jan 22, 2007
    Location:
    Fayetteville
    That's what I'm saying. It doesn't seem to vibe under acceleration, only at a cruise, where I wouldn't expect the pinion to climb as high. It also still does it in neutral at the same speed.

    I'm going to pick up some leaf spring wedges from O'Reilly's and try that this weekend, cause it's cheap and quick. If that doesn't work I guess I'll be going back into the axle.

    Sent from my E6910 using Tapatalk
     
  7. scrubber3

    scrubber3 Active Member

    Joined:
    Oct 18, 2009
    Location:
    Virginia just south of DC
    As was already stated, I'd check the pinion angle. Also, it could be the driveshaft itself. I once had this exact problem on a mustang.
     
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  8. Tim C

    Tim C Wizard

    Joined:
    Jan 22, 2007
    Location:
    Fayetteville
    Ill post some pics from my phone after this post, cause its easier, but I tried a few things on the car today. I originally had at static ride height my pinion up 2*. Trans is down 2* both lines are parallel like the top pic on my crude hand drawn Picasso piece. Today I stuck a set of 2* leaf spring perch wedges between the lowering block and axle. With them installed I measured 0* pinion and still 2 down at the trans like the lower crude picture. There was no change in my vibration. I also pulled the traction bars and tried it with the original 2* up pinion and the 0* pinion. No change so the traction bars in the actual photo did not cause or contribute to the vibe/noise. They are similar to the traction bars for lifted trucks and similar to what Shelby used on the original GT350 Mustangs in the 60's. There is a little bind in suspension at full droop but at ride height the bolts slide right in by hand.

    Now after driving it around several times and making changes a friend riding passenger and I both think this isn't a drive line vibe. It doesn't feel like any bad u joint or u joint angle vibe I've ever felt. The vibration is more like the car resonating from the WHA- WHA- WHA noise than an actual something out of balance vibration. Its almost like the same vibe you feel when the bass hits with a sub-woofer, but in time with the noise.

    Now while driving all around I decided to test something else. While holding a steady 68 mph (right in the middle of the noise/vibration range) I straddled the yellow on a two lane back road and swerved from lane to lane, not hard but enough to transfer weight. The WHA- WHA- WHA sound and vibe is there while going straight or when swerving to the left. But is seems to go away or get quieter swerving to the right. As soon as you straighten out or swerve back left it starts back up all while holding a constant road speed. Go above 70ish or drop to 65 and it goes away.

    Ive got to work on my brother's Camaro this week so I didn't tear into it cause I didn't want to tie up my lift, but next weekend I guess Ill inspect the wheel bearings and maybe carrier bearings. I've never seen a bearing only make noise in a narrow range like that, but shifting weight seems to make a difference just like all bad wheel bearings I've ever seen. If it does seem to be a bad wheel (axle shaft) bearing, I'm probably going to go ahead and put the big bearing ends on this axle so I can get rid of these expensive conversion wheel bearings.

    We jacked the car up on lift and ran it idling in 4th gear at 25 mph. With a mechanic stethoscope there is a louder sound from near the left wheel bearing than there is at the right or the center section.
     
    Last edited: Feb 3, 2019
  9. Tim C

    Tim C Wizard

    Joined:
    Jan 22, 2007
    Location:
    Fayetteville
    Maybe this crappy drawing will help visualize the pinion angles. Either way made no difference.[​IMG][​IMG]

    Sent from my E6910 using Tapatalk
     
  10. shocker998md

    shocker998md Well-Known Member

    Joined:
    Mar 6, 2007
    Location:
    grantsboro nc
    I hope you get it figured out, I'll be watching this one.

    I'm hoping to start my 445 build this summer, I cant wait.
     
  11. Tim C

    Tim C Wizard

    Joined:
    Jan 22, 2007
    Location:
    Fayetteville
    I tore it down today. The outer race on the left axle bearing is broken. I've never seen an axle bearing noise in a narrow range like that so I'm not sure if this is definitely it, but I'm going to put big bearing ends on this axle so I can do away with the conversion bearing. It may be I just can't hear it at lower speed over the 3" exhaust. I'll get a few pics of the carnage in the next few days. It's probably going to be a week or two before I get it back together at least. I'll update then.

    I love the 445. It just pins you in the seat pretty much whenever you floor it.

    Sent from my E6910 using Tapatalk
     
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  12. Tim C

    Tim C Wizard

    Joined:
    Jan 22, 2007
    Location:
    Fayetteville
    Here's the pic of the broken bearing. Left side is totally trashed. Rh bearing has a small hairline crack on outer race. There's less than an eighth inch of metal between the oring groove and the ball bearing groove where the piece broke off.

    I just replaced these after the power tour last June. They broke and were leaking when I got home. They were the originals from when I upgraded to 35 splines in 06.

    These didn't last 6 months, but I have been driving it more than ever. Dad's taking it to ecgs tomorrow for me, I'm having Torino housing ends welded on so I can run a set20 bearing. Hopefully I'll be able to drive it in a couple of weeks again.[​IMG]

    Sent from my E6910 using Tapatalk
     
    Last edited: Feb 11, 2019
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  13. shocker998md

    shocker998md Well-Known Member

    Joined:
    Mar 6, 2007
    Location:
    grantsboro nc
    Thats wild. Ive yet to bust a bearing in a 9 and ive ran some old clapped out shit. I had one start to growl bad on my 66 f100 but it survied 2 years of thrashing and 25,000 miles from me at that point.
     
  14. shocker998md

    shocker998md Well-Known Member

    Joined:
    Mar 6, 2007
    Location:
    grantsboro nc
    Do all the truck 9s run big outer bearings along with the fullsize cars? I cant remember but only have hands on experience with 61-79 trucks and a few galaxies
     
  15. Tim C

    Tim C Wizard

    Joined:
    Jan 22, 2007
    Location:
    Fayetteville
    I'm not sure what vehicles got which housing. I think it went by axle size. My Fairlane had 28 spline axles stock and it used the small bearing 2.8xx od. My 78 f150 had 31 spline axles and big bearings 3.150 od before the one ton swap.

    I think you could get a low gvwr f100 that had 28 spline axles in 78 and it used small bearing too. I remember having 3 options when I needed to buy axle bearings for that truck, a small bearing, a large ball bearing or a large roller bearing depending on the axle weight rating. So I think it goes by axle spline count.

    I broke a 28 spline stock axle shaft the one and only time I ever ran the car at the dragstrip. When I bought it the previous owner had began setting it up to race and that was my intention too. Before I finished building it up from where he started I got into wheeling and the car sat untouched from 07 til 2013 or so. At that time I started driving it more, then decided to make it a cruiser to drive to work or car shows since I don't care about drag racing anymore. I've been slowly fixing things in that aspect, I just removed the spool for a trutrac for example. The cage will be cut out in the future and the stock buckets and rear bench I have in storage will get recovered and re installed.

    Anyway when I broke the 28 spline axle, I upgraded to 35 spline Mosers. They have the same diameter as a 31 spline so they sold me a special bearing that has a larger inside diameter and a small od to fit the stock housing. The problem is they have to compromise somewhere so the races get thinner. Less than .090" in places. After I bought mine Moser had so many issues they completely quit offering the conversion bearing. Strange still does, but they recommend it only be used on trailered drag cars and not on cars that are street driven or road raced because the side loads will cause them to break.

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  16. grapehead

    grapehead Well-Known Member

    Joined:
    Mar 21, 2005
    Location:
    Raleigh
    Maybe the housing is tweaked from welding the back brace on? Have you put an alignment bar through it? New ends should fix that, but I'd want to know before changing them out.
     
  17. Tim C

    Tim C Wizard

    Joined:
    Jan 22, 2007
    Location:
    Fayetteville
    That's why I'm farming out the housing ends. I don't have an alignment bar. The axles slide in with no issues though. And I don't see any wear on the splines like I do on my obviously bent 14 bolt in my crawler.

    There are a few threads online talking about these bearings breaking in street cars. Looking at this one blown apart it's easy to see the race is really thin. It wouldn't take much of a pothole or side load to break it in my opinion.

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  18. WARRIORWELDING

    WARRIORWELDING Owner opperator Of WarriorWelding LLC.

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    My Classic Bronco 9 had 28 splines and the large outer bearing for what it's worth.

    I also think it's neat 9 inch rear ends usually bring out the line up tool when welding on the housing. Likely the sheet gauge design. However everyone tend to weld the ever living crap out of everything thing else with never a word of alignment tools or process.
     
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  19. WARRIORWELDING

    WARRIORWELDING Owner opperator Of WarriorWelding LLC.

    Joined:
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    Location:
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    Are you running an alloy axle? Could torsional twist on hard acceleration cause deflection that is killing the weak link?
    The related launch and snap from a loaded state kill the bearing?

    Arm chair engineering of course.
     

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