Differential

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beerdog

New member
I went to Mag's house Saturday to investigate this. Here is my opinions. i want to see what the rest of you think. He purchased a new trac-lock that was supposed to be a ford built 28 spline unit for a IRS. I was suprised to see the 4-spring clutch spring instead of the typical s-spring. We tore everything down except remove bearings and did not see any obvious problems with the carrier. The other thing we noticed their was a "Y" cast into the carrier. The shape looks like a Yukon Y. Plus the spring looks like what Yukon uses, although their website shows purple springs. Plus the ring gears was a very tight fit with carrier. When I rebuilt mine I used all ford parts and the ring gear was nice smooth fit with the carrier. The other observation is that when they rebuilt it they reused all the shims (pinion and carrier). I know this because the carrier shims were single pice shims. and the box of returned parts was missing all shims. My suspicion is who ever built it did not check the pinion depth or backlash. my questions

1. Did ford ever build posi's with 4-sping center springs?
2. Is it normal to have to remove material from the inside of of the housings? I would think not as you would have to be very carefull to remove the right amount due to carrier expansion being different than the gears. I did not have to do this with my posi unit.
3. I know reusing the pinion shim is OK as long as Ford gears were used, but simply reusing the pinion shims would not be OK?
4. If the carrier is not a ford unit then you definetly would be unlikely to get a good gear tooth pattern by simply reusing the shims?
5. It looked there was allot of clutch material and clutches seemed smooth. If friction modifier was not used would this be a problem?
 
driller

driller

El Presidente
beerdog said:
1. Did ford ever build posi's with 4-sping center springs?
2. Is it normal to have to remove material from the inside of of the housings? I would think not as you would have to be very carefull to remove the right amount due to carrier expansion being different than the gears. I did not have to do this with my posi unit.
3. I know reusing the pinion shim is OK as long as Ford gears were used, but simply reusing the pinion shims would not be OK?
4. If the carrier is not a ford unit then you definetly would be unlikely to get a good gear tooth pattern by simply reusing the shims?
5. It looked there was allot of clutch material and clutches seemed smooth. If friction modifier was not used would this be a problem?
Click to expand...
1. I've never seen a Ford Trac-lok with anything other than the typical S spring.
2. Not normal.
3. MOST of the time, I've seen the same pinion shims used when replacing ring gear and pinion IF they are Ford gears. Ford seemed to have had good QC on pinion depth settings across the board.
4. I've NEVER put a carrier in that used the exact same shim pack. It may be close but usually requires some shuffling of the shims. Whether the bearings are new or used plays a part in this as well. A lot depends on how close to perfection you are settling for on the gear mesh pattern.
5. Stack height is more of a concern with the clutches than the clutch surface. The clutches are designed to slip in normal use. More slippage equals more wear which results in less stack height.
 
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beerdog

New member
Yeah, I assumed automatically reusing the original stock carrier shims would not be a very good decision. I gues you could check it and get lucky but I would think that is unlikely. Especially since it is likely not a ford carrier. The gears were Ford.

- - - Updated - - -

Oh, and Perry said he found som aluminum in the housing. I think the person who rebuilt it made some errors.
 
M

mag

New member
I will be starting from scratch can anyone recommend a carrier or can I use a cobra carrier if I change the spider gears to 28 spline ?
 
germansheperd

germansheperd

New member
I just put in an Auburn Pro last week. Tru Trac can be made to work. Crazy i found out that Ford Racing no longer offers anything in 28 spline anymore.
 
M

mag

New member
Were any modifications done to the case or carrier to install it and did you have to you have to remove your cir clips from the axles ?
 
B

beerdog

New member
The installer also had to grind material from the carrier to avoid interferance between the carrier and the diff housing.
 
M

mag

New member
The openings are different but they do look similar. I will be buying a Detroit True Trac and will use this unit as a paper weight.
 
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M

mag

New member
Good news I am meeting with the owner of the dealership on Monday it sounds like he wants to make things right . If things work out that frees up money for a T/C :D
 
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