Noise, Rear End???

[BadBird]

I am having a problem Houston. When I turn the wheel while driving it slow there is a grinding noise that we think is coming from the rear end. Doesn't do it driving straight. I have added a posi=trac to the existing rearend.
I thought it might just need some posi-trac rear end additive so added two bottles of that but no success. Anyone with any ideas or past experiences please let me know. Thanks Larry

[Luva65wagon]

Larry - I've never owned a real posi-traction rear, but generally I think they are not very streetable. Others will probably have more information than I do, but limited slip rear-ends are better for the street. Essentially, as you probably grasp, when you turn a corner one tire has to travel further than the other around the corner (radii differences). So the only thing than can happen is the tire in the smaller radius has to "chirp" it's way around the corner. I think it gets worse the wider the tire.

That's my theory, but as I said, others who've owned them can offer some further insight.

[doghows]

I have had Detroit Lockers in axles before and they are NOT streetable. I think a Detroit is a bit more aggressive than a posi unit but like Roger said if it is engaged around a corner you will get noise and/or tire chirping. The growling noise would be the strain on the posi as the inside tire tries to turn faster than the outside tire. The additive for a posi unit is mainly for clutch wear purposes from I have been told. Hope that helps.??

[BadBird]

Thanks guys for getting back to me. I have had two cars with posi'trac. 57 checy, 67 442, and didn't have any issues with the car going around corners or these noises. I spent a lot of time on the internet last night and the two main causes that come up are......IF you are using a Ford rearend with posi you have to use the Ford additive. Nothing else works I guess and/or the springs in the posi are to tight not allowing the differential to work properly. Still studying but I am going to start first with the additive and then go to disassembly next. Larry

[doghows]

I just got the same info from my friend who sets these things up over at Randy's. He said absolutely add the Ford additive first, get some miles on it before tearing it apart. He said the noise should stop with the right goop in it?? Guess Ford is special that way??:confused:

[Luva65wagon]

Oh, so it isn't a locker - it does have clutches. Yeah, in that case - drain and use the right stuff first. Drive it a while before pulling it apart. Try and drive in straight lines. ;)

[BadBird]

I went down to Ford and talked to two mechanics that race Fords and they say that if it's a pure posi-trac like the detroit locker it will take a long time to work the noise out. But if it's a limited slip then it should be gone in a 100 miles or so. Wow, long time to put up with that but it only does it when I drive real slow and make turns. I put in new 80-90 weight and two bottles of the Ford Friction Modifier Additive. Drove it to get the rear end warm and then made a bunch of figure eights (per their directions). Noise is still there but I will take their advice and drive it more. If after awhile it's still there, I am going to take her to Northwest Differtentials in Kirkland and let them sort it out. Got about 20 miles on it and will try to get more tomorrow. Then if the weather is okay I'll be at the Maltby show Saturday. Larry

[pbrown]

Well Positraction has become a generic term people use now for all limited slip rear ends. Positraction is actually a GM trademark and was never available in any Ford vehicle. Ford offered Traction-Lok and Equa-Lock.. These need 90 weight gear oil with the Ford friction modifier or you can just use something like Royal Purple gear oil with has the friction modifier built in. You will get a lot of chatter if you run without the right oil.

There are some other third party clutch based and clutchles limited slip systems. Most also need the friction modifier added to the gear oil.

I find the clutch based Ford Traction-Loc systems quite streetable.

Now the Detroit Locker is a completely different thing. It is very noisy and is not well suited for street use. It is great for drag racing for those who also want to drive on the street.

I recommend that you pump the oil out and replace it with new oil with new friction modifier or some type of oil with the friction modifier built in. Go find a big open lot and turn some tight left and right circles after replacing the oil. This will get the oil worked into the clutches.

It would help to know exactly what you have because it certainly isn't a GM Positraction unit unless you have a GM 10 or 12 bolt rear end installed.

[BadBird]

Well, it looks like my fantastic neighbor (long long time ford mechanic) got this problem figured out for me. He found in some information on the "Bad Shoe" site that the traction system that I purchased is known to have too much tension internally with the spring/plate set-up against the clutches. So they recommend discarding the four springs and the bent type plate and go only with the shimming method. So he disassembled the rearend,(we could see where the parts were grinding and there isn't enough room for all the parts without having a binding effect, see pictures where one side shows hard grinding and other side shows deep groove) took out the parts, (measured the internal dimesions and verifyed the clearances were better and re-installed, and the noise is gone.
There was zero movement of the spider gears previously and according to BadShoe the gears should turn easily with a finger through the access hole.
The only thing we have to check now is to make sure the clutches fully engage and that both tires burn smoke at the same time. I will enjoy trying that out real soon.

[Luva65wagon]

So drive that thing over one of these nice evenings and give a little something to motivate me to keep going.

:3g: