9 inch rearend question.

bly · #1 (**permalink**) 08-15-2002, 04:18 PM

I installed a rebuilt 9 inch traction-lock rearend into my cobra. Have not drove it yet, but when i roll it in and out of garage, once in a while it will make a popping sound from rearend. Mostly when I roll it backwards. It does not do it all the time. Someone told me it may be the rearend needs to be broke in, as it is new, with new springs and other components.
Was wondering what you all thought of that theory, or have any other input for me, Any would be greatly appreciated, as always.

Bly.

Mr.Fixit · #2 (**permalink**) 08-15-2002, 05:14 PM

Did you add gear oil and Ford's "friction modifier fluid"? Is it a clutched diff or a locker with teeth?

bly · #3 (**permalink**) 08-15-2002, 05:33 PM

It has gear oil in it and i did add the ford differential additive, it is a clutched unit I believe. I have only moved this car in and out of the drive a few times 20 ft at the most, I did roll it into a trailer to take it to paint shop and it made no noise at all then.

Bly.

427sharpe · #4 (**permalink**) 08-15-2002, 07:21 PM

A lot of locked differentials make a slight pop when in reverse rotation because you are over-riding the torque differential, much the same as when you turn corners and the inside wheel has to turn at a slower rate than the outer. You just don't usually notice it with the noise from the motor, drivetrain, road, etc..
Keep an eye on fluid level, keep in the FoMoCo additive and check air pressure regularly because an underinflated tire can cause a lot of wear in a locked differential. Mind these things and I think you'll be fine.

justa6 · #5 (**permalink**) 08-15-2002, 08:49 PM

Hi, I think the replies are correct about the lube working its way in to the clutches and smoothing things out.

I did want to make a comment on the Ford 9" as I also have one in my Cobra. Its a great rear BUT something I didn't know (you might) is that if you ever plan on taking your car to the drags and you are going to use slicks be aware that IF you heat the slicks to get them to bite correctly your Trac-Loc is going to go away.

I ended up getting rid of the clutch type system and went with a Power Trax unit that has no clutches and is not a "locker". If your not going to take it to the track (drags) and use slicks then enjoy your 9" as it will probably last a long time.

Regards,

A Snake · #6 (**permalink**) 08-15-2002, 10:59 PM

Bly,

A thought for you. The clutches in the diff. only slide past one another when either one wheel spins, or when you are going around a corner. Going straight in and out of the garage, your wheels are both going the same speed, so the whole differential assembly rotates as one piece. Not even the spider gears move.

I'd have a look at your universal joints if I were you. A note for you on ujoints. When installed, the angles of the universal joints must match at both ends of the drive line and be absolutely in line with each other. First draw two parallel lines on paper, say an inch apart and 3 inches long. Next, draw a diagonal line from one to the other. Look at the angles, they both match. That's how the angles work. Next, look down the drive shaft like sighting down a rifle barrel. If the joints are not dead in line, there's a problem.

You have a pretty short drive line in your car and less margin for error than say a passenger sedan or a pickup which have long drivelines.

Put the rear end up on a floor jack and rotate a wheel too. Then you can look and listen at the same time. Don't get under the car though, unless you have axle stands under the axle housing.

Hope this helps,

Al

Mr.Fixit · #7 (**permalink**) 08-16-2002, 09:39 AM

New diffs do sometimes have chattering action at the clutches until they get driven. When you're pushing the car it feels like the tire are running over zip-ties on the garage floor.

Ron · #8 (**permalink**) 08-16-2002, 10:04 AM

Bly, I recently changed the gear set in my 9". I also have a disc posi ( auburn ). My clunking went away after about a mile of driving.

bly · #9 (**permalink**) 08-16-2002, 11:01 AM

Thanks or all the good info you guys have givin. I have not turned the vehicle at any sharp turns, just straight in and out of garage, That is what is concerning me. I have not checked the u-joints and angle yet as it is still in paint shop, (after two months) it better look pretty d*** good after that long. Hopefully the rearend just needs to be broken in. Again thanks for all the input.
Maybe one day i can answer someones question on here. (Any one need some advice on a jet engine?) Thanks. Bly.

justa6 · #10 (**permalink**) 08-16-2002, 06:38 PM

I'm in Ground school right now. My "motors" are going to be PW 4056's X 4. Airplane is 747-400. I've been flying the DC10 with GE's which I liked. The Pratt's are DEC so not much worry about "overboosting" the little puppies...

I've heard we've had pretty good luck with them on the 400. They seem to start real well in the Simulator

Somewhere I seem to remember that one pound of thrust is equal to 1 Horsepower at 300Knots. Sound right? If so then they are 56,750 HP each times 4 would be right around 226,000 HP. Hmmm. There's got to be a way to "steal" a couple of those ponies for my Cobra

Regards,