Ford 9" Whoa's

So here I am - at another crossroads during my muscle car build up. I am in the process of building my choice street machine, and the funds are dwindling. I am sure I am the only one that this has occured to right?

Anyways, long story short. I am looking for some ford 9" rearend advice, as I wait until next year to fund doing this right. I currently have a noisy 3rd member (3.70 gears/28 spline) sitting behind a brand new 500+ horse 402 BBC and a new TH400 trans. It makes a nice noticable hum (not to mention vibration) at about 50 MPH. It seems to only happen when there is positive throttle engagement. Once I let off, it goes away.

I would like to go with the Strange 3rd member/rearend setup, 33-35 spline axels, etc... but this will be next year. Any recommendations on rebuilding/fixing the current config, or would it be approx the same cost as just putting the money into my new config. I think I can make it thru the summer, but its annoying as hell, not to mention I am having fears of breaking the rear-end thus ending my radical summer fun.

First you should have your driveshaft balanced. Mostly those vibritations coming from unbalanced items.

It is a 15 minute job (without removing). Here in Germany they charge about 40 Dollar for that. Shouldn't be more in the US.

check pinion end play front to back.. most factory setups used a crush sleeve. it looks like a piece of exhaust tubing. it is deformed when you preload the pinion during setup.. that much motor can further deform it giving more endplay. the racers would set it up with a crush sleeve then take it apart and machine a heavy wall spacer the same length. you might be able to add spacer shims until you get a new one set up right. there should be some rebuild info on the net

I think DennyW is probably right. I had a vibration on my '79 1-ton 4x4, described much the same way. I punched the throttle on the freeway going 65 mph when that front u-joint, or whatever was out of balance, finally let go. There I was with the front of the driveline smacking the freemay coasting to a stop. I'm lucky it didn't roll me, it was just a tube bolted to the rear axle, I never found the other parts that let go. Any vibration I've ever had has either been a tire out of balance or driveline related.

As to your current axle, I think it would be cheaper in the long run to beef up your current 9 inch rear, rather than start with another one, jmo.

Here's another thought, the more I think about it, the more I think your vibration IS driveline related. Do you launch it hard and such? That's a big motor, and I'm tending to think your driveline might be ever so slightly twisted.....anything is possible, however.

Thanks for the information guys. I have not really had my new 402 in that long, but the car used to have a 454 (previous owner spun main bearing) so I replaced with this 402 that I couldnt pass the deal up on. Anyhow, I have never had the driveline balanced, so I will start there. I will replace the front/rear u-joints (reminds me of my 4 wheeling days - simply didnt think to go there again), but if this fixes it, it will be a cheap and simple place to get corrected. If that doesnt do it, I will dig into the third member and check out that crush sleeve. Does this sound like a workable plan? I am thinking cost and ease, then going to the more expensive items last. BTW - launched the car hard a couple times last night at it seems tight until you get it upto regular cruise speed (65 or so) then the spinning whine is oh so present. It almost sounds like a bad bearing, but I am just stabbing in the dark. Also when I did a long roasting burnout with the line-lock on, the right tire left a 60 ft strip, while the left side (drivers side) left about a 30 ft strip. Could this be a clutch or something in the 3rd member that is slipping or in need of repair? I have been a chebby guy and new to the whole ford 9" deal. Not sure if this is signs of a limited slip, fault posi, or what?

Do yourself a favor and take the drive shaft to someone and have it checked. It could be bent or bad U-joints. If you don't have to get into the rear end, don't. If you don't know antthing about it, do a search on the net for 9" ford rebuild. You will find some good information. I bought a complete rebuild kit for mine for around $90. Did not include axle bearings.
Ed