The past couple of days I've been disassembling my ford 9" in the studebaker for a couple of reasons. I had a leaky axle seal and the 500 mile fluid change came to get rid of all of the disc material (4.11 posi unit). After spilling half of the gear oil on the ground, I wiped it up with some paper towels and felt a sharp piece of metal in the mix. I am no expert on differentials, so I don't even know the technical terminology. It appears to be part of the posi unit, spider assembly. But what cracked looks like a roll pin, and then the "pin" that is perpendicular to this "roll pin" looks to be cracked internally as well. I'm just curious as to: What are these pieces and what are their purposes? Why a failure at only 500 miles? And what anyone recommends (complete rebuild??) This pic shows how the "roll pin" is supposed to look: This is how the one looks: This is the "roll pin" that I found in the oil: Here's a pic of the internals, with it shifted one way: And shifted the other way, to show that it appears to be cracked:
It looks like one of the spider gears may have galled and seized to the cross shaft causing it to spin and shear off the roll pin. I would disassemble the unit and inspect it for damage. If it's that new talk to your supplier about a warranty replacement.
Was it new 500 miles ago or was it a used part assembled into the housing 500 miles ago? Something seized or jammed in there. You say it had an axle seal leak - it wasn't run dry, was it?
Good question...but if it was leaking at an axle seal, that would suggest a high level of oil. Would still do a close check, though. With the scarcity of American bearings today, (offshore junk being re-boxed and stocked) I am wondering if differential gears and other hard parts are coming here from Bulgaria, China, Taiwan...(and other exotic and romantic places) Quality control and Rockwell are not paramount on their agenda. I had a 9" do the same thing awhile back. It had been 'repaired' with misc. used parts, by a differential guy and I needed one for my truck...nice deal, 3.70 with 28 splines, $50. IT went about 700 miles, then 'crunchy' around corners...when I disassembled it, it was similar to this one, but the carrier cracked at the pin, the ring was jammed on, and the spiders were galled to death. Plenty of 90 wt., the cause was mis-matched spiders/side gears. I needed a 3.0:1 anyway.
It was a brand new limited slip unit 500 miles ago (whether or not the guy just rebuilt one or actually used new components is something I need to find out). Unfortunately, the warranty was time based, and I bought the pig 1 year into my 3.5 year build. It wasn't ran dry. I made sure to keep up on the level and keep it topped off. After removing the new axle bearings (which were also replaced 500 miles ago), the seal surface on the axle was marred, causing the leak. This was polished. I did a lot more research and am more familiar with what went wrong now. The only problem is, I wonder if the entire posi carrier was a cheap reman from the beginning, or if the components were just rebuilt from stock. If it was a cheap reman, I might consider buying a new unit. Otherwise, I am going to attempt my first rebuild (thanks to HAMB resources). Hopefully to consist of changing the 2 or 4 spider (pinion) gears, pinion shafts, and roll pins, along with a complete bearing swap. I will have to figure out whether the guy shimmed the clutch hub properly. I noticed that if the posi unit is a stock ford setup, that tool T68P-4946-A is required to check the clutch hub clearance. Anyone have a way to find this tool, or determine a better method of using a dial indicator?
did you run friction modifier in the oil for the posi? was it jerky going around corners? if its biting and slipping that's a lot of shock to the carrier, that could have done it...
Yes, I added the modifier. It wasn't jerky, and in fact it felt like butter. I did a burn out or two, but geez, isn't that what these things are for . This is why I want to check the clutch hub for proper shimming.
Does anyone have any experience with the detroit truetracs? I was doing a lot of research and really like the setup. I have a couple of concerns, however. First off, I must explain how my car is set up. I have a Chrysler 383 with 4 speed tranny, ford 9" 4.11 gears. The tires on the back are 35" tall Mickey Thompson mtz. I am starting to wonder if the roll pin sheared due to the massive tires creating heavy loads and rotational inertia, along with the semi powerful motor, doing big burn outs and such. I read that eaton originally called out a max tire size of 32" for the trutrac. This caused me to wonder if I need a beefy diff for my large tires and power combo. Eaton now says the truetrac can handle up to 38" tires. However, most people who use these are screaming their motors in mud, compared to me who wants to break em loose on the pavement. I've heard of people blowing them up, but most reviews are extremely positive. So, I don't want a locker and I don't want an open diff. Would the truetrac be the next best thing for my unusual setup?
I suspect that the pin is loose in the hole which will put pressure on the roll pin, or the pin broke. The stock pins are pretty brittle. They need to be hard for the spider gears to turn on them. When we raced dirt track, some would buy a minispool that was a single piece that took the place of the side and spider gears and was held in place by the pin. They broke the pins pretty often. I welded our side gears into the carrier. Much more surface area to hold the the torque instead of just a couple of teeth on each gear. Have you disassembled the unit yet? Something doesn't look right for that to be a limited slip differential. Truetrac is a pretty strong setup. I've worked on forklifts with them in. Operators would break axles when they tried to make tight turns with heavy loads on concrete. I had Strange make a pair and they didn't break, neither did the Truetrac. As with any differential, wheel hop is the enemy. Is this a leaf spring setup? Do you have any traction bars on it?
I run a TrueTrac in a Dana 44 in the front and an Electrac (effectively a lockable Truetrac) in a Dana 60 in the rear of my daily driver. It has seen 40,000 miles with this setup, with 36" tires. Over the period, the rig has seen some of the toughest terrain the West Coast has to offer. I inspect both differentials often, and have yet to see any sign of damage, or even wear. If I can't break one with a transfer case with a 10.44:1 low-range, a 3.83:1 first gear, and 4:88:1 r&p, all multiplying 250lb.-ft. of torque, you won't either.
Well I'm not sure what I have. I took apart the diff today, and there is no clutch hub to be found. It has 4 pinion gears, and the side gear which is supposed to rest against the clutch hub just sits against the side hat casting. But, it has the little cage that has the 4 springs in it to press against the side gear. So, does that mean it is an open diff, or a posi without the clutches, or a locker, or? Can someone explain the difference between an open, posi, and a locker. I feel that there are components missing, or that it was a half ass posi. Well, if it is true that I have an open diff, I definitely got screwed. Now I need to figure out what the hell this guy put in here. I have a coil spring set up, with a triangulated 4 link. So I don't suspect that there would be any wheel hop. Even if my axle is not true to the front axle, I wouldn't see this creating such an issue. I wonder if this guy gave me a complete used set up. I need to make sure these gears are 4.11 and that they are not worn. Thanks gimpyshotrods, I think a truetrac would be the right way to go.
First off, there are both two pinion and four pinion open/standard diffs. The side gears/axle gears do not have any splines cut into them toward the outside of where the open axle gears have only thrust washers. Second, the Trac-Lock/Ford posi will always have splines on one or both axle gears. Someone clarify that. The splines are for the clutch discs to engage to as the diff housing is also cut for tabs of the steels to engage to. Most common is 4 tab, least common is 5 tab steels. There is also a dose of coil springs that are very similar to motorcycle clutch stuff. 28 or 31 spline axles are normal in most of these options. I will guess not all. If you don't have clutch pieces that look like small motorcycle clutch parts, you won't like the answer of what somebody sold you. Buyer beware, just like buying a house.
Contact Hemi Dude here on the HAMB... Sets up and rebulids center-sections, re-splines axles, custom builds housings all the time..
I've seen open rears gall that pinion shaft and break a solid lock pin on GM pickups used for snow plowing. That happens in cold weather when the oil is stiff and then getting stuck and overspinning one wheel.
http://www.eaton.com/EatonCom/Produ...roducts/Differentials/DetroitLocker/index.htm And then you have the guts of Detroit Lockers from pickup truck size to stuff I know better. F&J is along with me. Spin tires with an open diff long enough, carnage will happen. Blue steel is the result, french fried blue steel. Neat to look at, expensive to replace.
I have an open ford 9" sitting here, and I took that one apart too. The only difference between mine and the open is that my "posi" has the center block for the pinion gears with 4 holes, the 4 springs and the retainer. But my "posi" does not have the clutches.
Sorry you got screwed.The pinion gears allow each axle to turn independently. One can turn forward and the other backward. The bad thing about them is that the wheel with the least traction gets all of the power. A limited slip uses clutches to lock one of the side gears to the case under power. The torque forces the clutches together but if one wheel is forced to turn faster than the other[turning a corner] the clutches unload. GM called it Positraction and it was put in many vehicles. Ford limited slip units were rarer. Ford used a Detroit Locker which is a set of gears that lock together under torque. It sounds like a ratchet when you turn a corner. The True Track uses gears to connect the wheels together. The cut of the gears doesn't allow the wheels to turn at different speeds unless one wheel is forced to turn faster than the other so it provides equal torque to both wheels. Eaton has information on both on their website.
something dont sound right, if it has 4 springs in the center block, they are there to pre-load the clutches in a posi,, the block would not have the springs in an open rear. and the clutches are only on 1 side of the case, between the spider gear and the case. like this[/IMG]
Yea, what a hodge podge piece of junk. Well, time to start from scratch, maybe try to find a nodular case at Iola, and then build it up from there. Got to see if my gear set is ok or not. Thanks to all for the help.
Sounds like it might be an Auburn (cone) type of posi, where there are no clutches, but there are cones on the outside of the axle mounted spiders and a matching cone milled into the differential carrier. Post pictures of what you have, and we can tell you for sure.
what you have was called a poor mans posi back in the day they took a 4 pinion open carrier and put the posi block in it with the four springs and the small cover plate some thime they put a extra shim under the side gear to force it closer to the spider gears so when you bolt the two sides to geather it puts the gears in a bind and both tires would lock up the problem is every thing is in a bind and it dont last long or brakes i hope this helps >>>>Clay
You wouldn't believe the amount of metallic shavings I found in my housing after 500 miles. That carrier was not set up correctly at all. I ended up purchasing another carrier, this time a new yukon limited slip with new 4.11's. I threw it in the housing just to see how it felt, and it ALSO feels a little strange. Maybe this is normal, but here's what's going on: When you turn the yoke back and forth to hear the backlash, you hear more than one gear "click" when it hits. I showed it to a gearing engineer here at work, and he said maybe it is the bearings re seating/??? Also, if you rotate back and forth, you get about 1 ring tooth of a turn with very easy turning. After that (if you are continuing in the same rotation), it tightens up. Could this maybe the slop in the pinion bearing? I would assume that it should always be tight, regardless.
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