'57 Ford Fairlane HO 302/new AOD just installed (TV cable professionally set) New balanced driveshaft 3.56 rear end I started road testing my new engine/****** swap and everything is working very nicely except for a driveline noise at cruise. At lower speeds I don't hear anything. While accelerating I don't hear anything. Once I get above about 40-45mph, I get a vibration type of sound only when I let off the accelerator pedal and coast. It sounds like it's directly under the floor shifter, but I took a p***enger on a road test in the back seat and they could her it resonating in the back as well. I checked the ****** and engine mounts and everything is nice n' tight. There is no lateral play in the ****** output shaft with the driveshaft installed. There is no lateral play in the rear end yoke either. I can rotate it very lightly (a degree or two) but I don't see that as a big concern. It might be the rear u-joint. It's brand new, but I may have f'd it up when I installed the driveshaft. It's the old Ford "clamp-on" type of connection at the rear end. I now know that this is a low torque application and the included tabs hold the bolt heads in place. I tightened them down pretty tight, so I may have crushed the needle bearings. The new u-joint will be here today and will be installed by the weekend. Another oddity is a leak at the rear extension housing of the ******. I made another boneheaded mistake here. When I greased the inside of the slip yoke to install onto the output shaft, I also greased the OUTSIDE of the slip yoke and I'm hoping that's the cause of the leakage past the seal. When I pull the driveshaft to replace the rear u-joint, I'll clean up the yoke and seal, too. Should I replace the seal and bushing while I have it down? The transmission is newly built, so it shouldn't be any kind of a wear issue. So, my hope is that my two boneheaded mistakes are the simple causes of both issues. Any input while I have the car up on the lift this weekend would be much appreciated.
***uming you didn't change the rearend or pinion angle of the rearend, from what you've described I would try u-joints first.
Put her up and jack stands and carefully run it . I had a simular sounding problem , I mean a loud noise at like cruze speed or when you backed off and run a steady MPH, if I was on it it wouldn't make any noise. Drove me nuts, I had the entire rear , housing, ( thank God for 4 link) the axels, gears, etc, etc. out of that peice of **** 4 times. I was at the point I was going to hammer the piss out of it untill something left go, after changing both u-joints, the ****** tail shaft brg. re-balancing the drive shaft, inner/ outer axel brgs. It would up being a knife edged ring gear. One good thing I can now drop the *** out of that thing in about 5 mins.
Check the length of your driveshaft. A friend of mine had the same problem years ago and his driveshaft was made to short and would vibrate because enough of the yoke was not into the trans tailshaft. When coasting the rear end is spinning the trans, when you get on the gas the trans is spinning the rear end. If the yoke is not in far enough into the trans it orbits around as it spins, if that makes any sense.
Interesting. I'm pretty sure the driveshaft that I had made is the right length because Iw as super careful with the measurements, but if I remember correctly, there are a few different lengths of tailshaft housings for the AOD. That may mean different lengths of slip yokes are available. I picked one for a Mustang because that's what the SBF came from, but I really don't know what kind of car the ****** was in. If the rear u-joint doesn't fix it, I'll look and see if there is a longer slip yoke available.
R'dave....do you have some angularity in your U-joints. You need some. Are your ****** and pinion centerlines parallel ? Are you exceeding 3 degrees in the U-joints. That wouldn't be the best.
I'll have to measure to verify. There is some angularity, but not very much. I also need to verify the pinion centerlines. For some reason, I was thinking problems in this area would cause the opposite - vibration and/or noise while accelerating and not at coast like I'm having. I'm a total newb at this part of a build, so it's also very likely that I'm completely wrong!
Still buzzin'. I changed the rear u-joint and the transmission output shaft seal this afternoon and just got back from a test drive. It sounds pretty much the same.... Under 45mph - nothing Over 45mph - nothing when I'm on the gas, but it makes a "buzzing" sound when I let of the gas pedal. As soon as I get back into the gas, it stops. Weird, weird, weird. I'll measure driveline angles tomorrow and see if there's anything there. The only thing I noticed when inspecting is that, at least with the naked eye, the driveshaft is pretty straight between the rear end and ******. There doesn't appear to be much of an angle, which I know is needed. I'll have to double check with some real measurements to make sure. Other wild *** guesses are: 1. Maybe the e-brake cables. They run directly under the exhaust. Could the cables be buzzing against the exhaust when I let off the gas? Not likely, but possible. 2. Could something be wrong in the ****** that would cause this? It sounds like it's almost directly under the shifter (floor mount Lokar). That puts is right around the tailshaft housing. 3. Rear end problems? Again, it seems like it would happen more than just 45mph+ at cruise if this was the case. I would also suspect more of a clunk than this damn buzzing sound. This **** is bugging me. If I KNEW it was just an annoyance and not something bad about to happen, I would just crank up the radio (or take the gl*** packs off!). I just worry that this is something that's going to break while I'm hauling *** down the interstate.
I just replaced a c-4 with an aod in my 40 tudor. had two problems. 1. the aod was used, worked great except a vibration at about 60mph. this turned out to be a bent output shaft in the aod. all the experts said this virtually never happens. well i found the one in a million. 2. had a noise similar to what you describe on deceleration from about 70 mph on .it was a noise as opposed to a viabration.last night i raised the rear trans mount as much as i could to get about 5.5 degrees down u-joint angle. rear is about 3 degrees up. i also greased both joints. this seems to have solved (fingers crossed) the problem. dont have many miles on yet though. i know the front joint angle is excessive but its the best i can do without major surgery. i'm interested to know what you find. keep us posted. ron
Found what should be the culprit. I put the rear up on jack stands yesterday and ran it fast to see of the driveshaft was doing anything weird. It was turning straight as an arrow. Before I set it back down, I grabbed one of the rear wheels and gave it a good shake. There it is! I got someone else to shake it while I was inside the car and the exact same noise that I was getting while driving was there. I pulled the 3rd member and brought it, along with the axles up to the driveline shop. I went back up there at lunch today and they showed me the bearings. There were pits in the bearing sleeves and a fair amount of play. Looks like this car sat for a long time at some point before I bought it 4 years ago. For whatever reason, this noise never occurred with the old inline 6...of course, it never went quite as fast as this 302HO either! The 3rd member and axles (bearings) will be done tomorrow so I'm very optimistic that I found the problem. While I have everything apart, I'll go ahead and replace the brakes and other ***orted **** on the rear.
Thanks, hope that does it. Let us know if it doesn't. Mine is okay still, don't know if the angle change or grease fixed it. I suspect the angle. I'm gonna try and get it better still. Ron
The rear end rebuild got about 80% of the noise out. Still does it a little bit at high speeds, but man did the rear end ever need the rebuild! Hard to believe I drove around with what looked like mol***es back there for 5 years. All of the seals were the original leather ones, too, all the way out to the axle ends. I also took the opportunity to go over the rear brakes while I had everything apart.... Speaking of the rear brakes - I replaced the rear shoes about 4 years ago, apparently ON ONE SIDE! When I pulled the left rear drum, the linings were brittle and falling apart. The right side was almost as good as new. I found the box in my garage with the other pair of shoes. Not sure whether to attribute that to ADD or beer... I replaced BOTH sides this time, turned the drums and replaced the wheel cylinders. Stops a hell of a lot better now! Next on the driveline noise will be shimming the rear ****** mount up a little bit to try to get a better angle.
Fixed it!!!! I fabbed a 1" plate and shimmed the transmission up, um, 1". Drove her home from the shop/Coollows clubhouse this evening and the noise is completely gone. I'll have to jump back under the car tomorrow and fine tune the shift points on the Lokar shifter (all-thread rod), but other than that it's 100% better! Thanks again for the feedback and advise. The good ol' HAMB has gotten me out of some jams over the last year of this build!
Congrats on the fix.I need to get a better angle on my front joint as well, may have to bite the bullet and do some floor surgery. Ron
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