I have just run in a new Ford 9" in my 68 and I think I have a pinion seal leak. In addition I also have a deceleration vibration at highway speeds. I want to check the torque at the pinion nut. From what I hear I can torgue it to 100 ft/lbs and be safe??? Should I back it off and apply new thread locker first then do this?

Check it and see if it is tight first. If it is loose then remove it and apply the Lock Tight. If it is already tight then you may have a pinion bearing going bad.

I tightened it to 100 ft/lb and it did not move. I put everything back together at that point to test drive. I had replaced the rear u joint and raised the rear suspension 3/4" (I lowered it too much last fall). Test drive was good; no vibration. I will drive a bit a recheck pinion seal for leak. I may have filled it too far befor Power Tour..could that cause the leak? Thanks BGH

I doubt that over filling it would cause it to leak, but it is possible.

Unfortunatly after driving the car to the St Ignace show in MI I found the vibration is still presant. It is there cruising at 58-59 MPH and any time I slowly decelerate from highway speeds. If I completely lift off the gas it does not vibrate. I also I feel it to a lesser extent all the time over 70 MPH. This is a strong vibration that comes through the whole car and rattles everything.
I have changed wheels with same result. The car is back on the road after installation of a ford 9" with new gears and trac lock. The pinion was set at -1 to 2 degrees but I will recheck it. The rear was lowered 1.25" with blocks. The drive shaft is the same and did not vibrate before. I also have a pinion seal leak on the new seal. Thanks!

Sometimes the pinion and pinion housing can be removed from the 9" Ford without removing the rest of the differential case. There are 5 bolts that hold it in place. You may be able to remove these bolts and pull the pinion housing out. If it will come out then you can check the pinion bearings without having to go any farther into the rear end. Be sure to keep up with the shim that is behind the pinion housing. There is also an o ring that goes around the pinion housing. Sometimes the pinion will bind against the ring gear when you try to remove it. If you get the pinion housing loose but can't get it to come all the way out then you will have to remove the differential case and loosen the backlash to get it out.

I will get under there tonight and see what it looks like, I will get back to you. Thanks Freddy.

I jacked the rear end up last night and made sure to eliminate the wheels and drums as the cause of the vibration. The vibration in this set up was still there but a little less intense and did not come in at a specific speed (was worst at 58-59 MPH on the road) but it comes on at 60 MPH and just gets worse the faster I took it. I got under the car with my wife on the gas (God help me) and whatched. It seems very difficult to actually see something vibrating but I did not see anything out of the ordinary. I was suprised to see the actual amount of pinion elevation as the car reved up. Hard to guess but the pinion seemed to rise a good 6-7+ degrees or more as the gas was on. I wonder if I should get some shims and play with the pinion angle before I dig into the rear or tranny. I did set the angle at 2-3 degrees initially. Any input appreciated.

You may want to invest in some kind of traction device to help control the spring wind up. If the pinion angle is changing that much then it may be hard to eliminate the problem. The Cal-Trax bars or Competition Engineering J bolt bars seem to work well. This may help. If you have a set of traction bars on it already then you may want to raise the front so that the snubber is closer to the spring. I guess you have already checked out all of the u joonts and checked the drive shaft for dents. You may want to remove the drive shaft and lay it on a flat surface and roll it. If it is bent then it will show up when you do this.

Yes I have checked all that so far, even replaced the u joints because you never can tell. I was thinking of setting up a makeshift pinion "snubber" for testing the car up on jackstands. If I limit Pinion movememt that way and the vibration is gone then , like you said, I may have to get those cal-tracs I wanted!

I set up the temporary pinion snubber that did limit the pinion movement but the vibration persisted. I have since had a new bushing intalled in the tail housing of the tranny. I am testing that tonight.
I was thinking... my driveshaft did not need to be changed in length when I went from the 10 bolt to the Ford 9". The distance from tranny to pinion was about .5" longer after the swap but the shaft seemed to engauge the splines O.K. Can the driveshaft be too short? I am certain that the slip yoke fully engauges the tailshaft bushing..

Hey J Early, i am in the same boat you are in i just changed my 68 Camaro to a Ford 9" and my pinion seal is leaking too.Boy have i had a time, i first set my perched at 6 degrees down and welded them up and painted my rearend before i installed it (rookie mistake).When i put it in the car the rearend set 6 degrees down plus the 6 degrees i put in it for a total of 12 degrees.I drove it about 2 miles with bad vibration, took it back home and u joint was hot.I jerked it back out took torch cut perches off bought new perches put it all back in, adjusted rearend to 6 degrees (down) tack welded perches took it all back out again welded perches painted it and after i get my pinion seal replaced i am going to re-install it and i hope i do not have any vibration.Man i am getting good at removing and installing this thing.Mine was a 28 spline 3:89 ratio w/mini spool

J Early i got a few more questions for you.Is your 9" a 28 or 31 spline?Trac-loc or open?Was your axle tubes tapered down towards the wheels?

It is a 28 spline with moser axles and a trac loc from U.S gear. Housing is not tapered. I have yet to test drive after the tranny bushing due to my schedule.

Just to follow up..I took the car out for a test drive after replacing the tranny tailshaft bushing and I would say the vibration is 80% gone. I had to wrok hard to find a spot where there was a little vibration. If it comes back the more I drive then I can guess the drive-shaft is wobbling enough to wear out that bushing.

I have a 67 that I swapped the 10 bolt for a ford 9". Everything on the whole car is either new or rebult. I have no vibration, but my pinion seal leaks. The pinion angle seems to be fine and the pinion nut is tight. I think I'm going to blame the leak on the Mobile 1 synthetic gear lube till I find out different.

I am running RED LINE synthetic.
I found the axle housing vent was leaking a little and it is close to the center section on the axle tube. I made a 3" vent extension and so far the rear end looks good for leaks. I am taking a 50 mile ride tonight so I will find out for sure if this cures it or if it really is a pinion seal leak. I did not think the oil could wick forward and make it around corners to the pinion but who knows?

Well the vibration did return. It increased to the amount it was at before after getting back from the Goodguys show in Wis, about a 400 mile round trip. I just put 2 degree shims in last night, moving the pinion up since it is a decelerating and highway cruising vibration. This did nothing. I guess I will turn the shims around and go 2 degrees further down.
Can a bad pinion bearing do this (new timkin bearings)? Can the pinion yoke be out of round? This is starting to get on my nerves! Thanks.

How are you measuring your pinion angle? It sure sounds like that's the problem. Explain it in detail.

Lee

Are you using the original yoke on the rear end? I have seen several of the new yokes that have the locating tabs machined off center. This would allow the u joint to be off center and cause a vibration.

Pinion angle was set using an inclinometer. Angle of the tranny output shaft was measured at the slip joint yoke with the drive shaft on, then the angle of the pinion yoke was measured and set at 1.5 degrees down from parallel to the tranny output shaft. Tranny was at something like -3 degrees and the pinion was then set at +1.5 degrees.
I did flip the shims around last night and my test drive this morning seems to be improved, but not gone. Maybe 50% improvement, but now I feel a lower frequency hum in the seat of the pants with cruising 30-40 MPH that was not there before??
This is the original pinion yoke and I have considered swapping this out or at least trying to find the runout on it.

j Early - I believe that is wrong. That was how I was doing it until I got schooled by some guys at the track. While the trans angle is important to the drive shaft angle what you really want is the pinion angle relative to the drive shaft.

What you need to do it measure your drive shaft angle at the pinion end then drop your rear driveshaft and measure the pinion across the yoke. This is the angle you want to get right to eliminate your vibration. You need to be careful as to what is positive or negative angles and how they add up. If your drive shaft is down 3 and your pionion is down 3 then the total will be 6 down. If your drive shaft is 3 down and your pinion is 2 up then you have 1 degree down, etc.

When I did mine like you did I thought I had 1 degree down but when I did it the other way I had 6 down!

Lee

Now I am really confused. I follow basically what is outlined on the Inland Empire drivshaft website. They do state that the driveshaft angle to pinion should be 3 or less and likewise for the driveshaft to tranny angle. The main premise though is that the pinion is set relative to the tranny and not the driveshaft? It makes no sense to me at all why the vibration would get a bit better(50%) with moving the pinion down when my problem was on deceleration and cruising downhill!

Are you using the right size u-joint? Once, when I was young (and stupid ;) ) I swapped a 8.5 into an 8.2 equipped '70 Nova. No knowing any better, I kept the 8.2" driveshaft and u-joint. The stock joint did not fit the yoke properly, and it had a vibration, and regularly ate u-joints and beat up the yoke before I figured out what was happening. A new yoke and proper u-joints fixed it.

My u-joints are properly sized. I talked with tech at Inland Empire driveshaft and, other than pinion angle, he advised checking the shaft length. He stated that there should be 3/8" play at the slip joint...just enough to push it forward to get the rear u-joint off the pinion yoke. My slip joint is a good inch so maybe this is the deal.

Rather than lengthening my driveshaft, I am going to swap on a longer pinion yoke to make up the difference. I guess the car yoke for a Ford 9" is nearly and inch longer than the truck yoke.

What about drive shaft flex? I have seen cars vibrate because the drive shaft diameter was not large enough for the length and RPM that it was running.

I would consider something like that if it were not for the fact that this same shaft, joints and slip yoke set up ran just fine before, without any gearing change. If this does not work (new pinion yoke)I will probably have to pull the third member and have it rebuilt, even though it is all new. I am trying to line up a loner shaft from another Camaro that would rule out problems with mine before I do that however.