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Pinion nut pre-load

s550gtbase

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So I just got a diff assembly (used) and measured the pinion flange pre-load while the assembly is outside the car. It read 5lb in. Reading other threads it appears people are reading 35. Just want to mention that I didn’t do anything other than measuring. Is this normal?
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s550gtbase

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That is an indication that the unit probably has quite a bit of wear. Do you know how many miles on it. ? When you check the preload like this remember you are measuring differential bearing preload as well as pinion bearing preload. Did you happen to record the breakaway torque.? I would pull rear cover and do a further inspection.
Thank you for the response. The listing just said low miles so not sure the exact miles. I did not install the diff on the car. Is there a way I can measure the breakaway torque while the diff is off the car? Also do you know the preload range while the diff is off the car?
 

308 Cal. Bullitt

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I am not that shocked to hear a low mileage unit has only ~5"lb of preload. Measured preload is not always an indication of overall wear.

It's more likely from a few (or more) hard launches, reducing preload on the crush sleeve length, from shock load on the assembly. This is why some of pur clients will opt to replace the crush sleeve w/a solid pinion spacer, when doing this type of work/inspection. Especially if bearings all look good, but you decide to Fresh'n'Up the pinion bearings & install either a nee crush sleeve, or the more robust component-
a solid pinion spacer.

It's difficult to determine whether the carrier bearing friction
(by not having removed it)
is contributing to the 5"lb cumulative figure measured this far, from the inspection process you have done to date.

To be accurate in your preload evaluation- 1st remove the complete ring gear carrier assembly, after draining all gear oil obviously.
(keep track of the side shims on ea side of ring gear carrier, while not confusing them for the reassembly later..)

Then, properly check the pinion bearing preload, with no ring gear/carrier- installed, along with the ~2 quarts of gear lube being removed/drained.

Having done hundreds of rear diffs over decades, we can advise, based on what you see inside, & what is measured in pinion bearing preload.

Looking at the carrier bearings/races, as well, during this disassembly process, is a good idea. Obviously, you will look at the gear oil, for contamination of materials from wear.

Hopefully its all in decent shape. 👍
Keep us posted if you go further.
 
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s550gtbase

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Thank you very much for the reply. This is the first time doing this so excuse my ignorance. So that I understand correctly, to get a more accurate measurement, I would need to remove the diff cover, remove the actual diff (Torsen) with the ring gear from the housing and then measure pinion preload again while the pinion is still in the housing? Hopefully, I got this correctly.

Right now, I just used a beam 1/4 in wrench on the pinion nut to rotate the pinion and it pretty much rotates with very minimal torque. Picture below shows the measurements. I am planning to open up the diff tomorrow and see what happens. The ford instructions say to compress the housing with a C-clamp to be able to get the diff out. Let's see how I will be able to achieve this. Learning a lot during this process!

IMG_5191.PNG
 

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s550gtbase

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s550gtbase

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Here is an update. I was able to measure the backlash and it was about 0.015. Little bit over the allowed range from what I know. Do these numbers make sense? Hopefully
I’m measuring things properly.
 

bankyf

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I am not that shocked to hear a low mileage unit has only ~5"lb of preload. Measured preload is not always an indication of overall wear.

It's more likely from a few (or more) hard launches, reducing preload on the crush sleeve length, from shock load on the assembly. This is why some of pur clients will opt to replace the crush sleeve w/a solid pinion spacer, when doing this type of work/inspection. Especially if bearings all look good, but you decide to Fresh'n'Up the pinion bearings & install either a nee crush sleeve, or the more robust component-
a solid pinion spacer.

It's difficult to determine whether the carrier bearing friction
(by not having removed it)
is contributing to the 5"lb cumulative figure measured this far, from the inspection process you have done to date.

To be accurate in your preload evaluation- 1st remove the complete ring gear carrier assembly, after draining all gear oil obviously.
(keep track of the side shims on ea side of ring gear carrier, while not confusing them for the reassembly later..)

Then, properly check the pinion bearing preload, with no ring gear/carrier- installed, along with the ~2 quarts of gear lube being removed/drained.

Having done hundreds of rear diffs over decades, we can advise, based on what you see inside, & what is measured in pinion bearing preload.

Looking at the carrier bearings/races, as well, during this disassembly process, is a good idea. Obviously, you will look at the gear oil, for contamination of materials from wear.

Hopefully its all in decent shape. 👍
Keep us posted if you go further.

Where might someone get this solid pinion spacer?
 
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s550gtbase

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Well today has been eventual with the diff.

The first thing I did was to get the pattern on the rings. I thought I saw somewhere that posted what the pattern should look like but cannot find it. Here is a picture of what I got.
tempImagesSa47a.jpg
tempImageOGfEVB.jpg

While rotating the pinion to get the pattern, I would hear an occasional clunk when both gears were turning.
After that I decided to take out the carrier with the ring. I marked and removed the cap screws and the caps. Now I am thinking how to convince the torsen to come out since I did not want to compress the case. To my surprise, I grabbed the carrier with my hands and just pulled it out. There were one shim on each side (same size). This was too easy but being the first time I do this I have nothing to compare it to.
Next, I measured the preload on the pinion (by itself). There was no preload what so ever. The thing just spun when you touched it. So I decided to remove the pinion. First thing, I removed the flange. Again super easy. Held it with one hand and used an impact to remove the nut. I then used a 3 jaw puller and pulled the flange out.
Then I got a small block of wood and placed it on the pinion. Couple of light taps with the hammer and the pinion was out. Now, while inspecting the crush washer, it did not seem to be crushed at all. Again, since I have not seen a crushed crush sleeve before I am not sure what it looks like. But I assume it would be somewhat crushed? I had a brand new crush washer that I bought with a different kit so I compared the two. They seem to be the same height. Here is a picture of the new one (the one on the bag) and the used one side-by-side.
tempImageAOOy5k.jpg

I am not sure what to make of this. I think someone tried to install or rebuild the diff and gave up half way through.

Regardless, it has been a fun project so far and I am learning a lot.

What do the experts think? Am I on the right track with this?
 

JohnVallo

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A new crush sleeve will only be about 1/16” longer than a collapse one. Set them side by side on a perfectly flat surface. Then take a straight-edge and place across the new one, the old one should slide under the straight-edge. Then you will see it doesn’t take much to be collapsed. If you have a digital caliper, you can also compare lengths.
 

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s550gtbase

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A new crush sleeve will only be about 1/16” longer than a collapse one. Set them side by side on a perfectly flat surface. Then take a straight-edge and place across the new one, the old one should slide under the straight-edge. Then you will see it doesn’t take much to be collapsed. If you have a digital caliper, you can also compare lengths.
Thank you John. You are correct. I just measured them and it is a tad shorter. Is it usually so easy for things to come apart? Also any ideas for the no preload on the pinion?
 
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s550gtbase

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Also the pinion outer bearing is still in the housing but it has a lot of play. Does that make a difference?
 

JohnVallo

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Thank you John. You are correct. I just measured them and it is a tad shorter. Is it usually so easy for things to come apart? Also any ideas for the no preload on the pinion?
You should have had to pry the diff/ring gear out of the housing with 2 pry bars.
Should not have been that easy.
Could you tell if the Pinion flange had been off before,? The factory “stakes” the pinion nut to the shaft after preload. Was that nut staked on both sides before you took the nut off ?
 

JohnVallo

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Well today has been eventual with the diff.

The first thing I did was to get the pattern on the rings. I thought I saw somewhere that posted what the pattern should look like but cannot find it. Here is a picture of what I got.
tempImagesSa47a.jpg
tempImageOGfEVB.jpg

While rotating the pinion to get the pattern, I would hear an occasional clunk when both gears were turning.
After that I decided to take out the carrier with the ring. I marked and removed the cap screws and the caps. Now I am thinking how to convince the torsen to come out since I did not want to compress the case. To my surprise, I grabbed the carrier with my hands and just pulled it out. There were one shim on each side (same size). This was too easy but being the first time I do this I have nothing to compare it to.
Next, I measured the preload on the pinion (by itself). There was no preload what so ever. The thing just spun when you touched it. So I decided to remove the pinion. First thing, I removed the flange. Again super easy. Held it with one hand and used an impact to remove the nut. I then used a 3 jaw puller and pulled the flange out.
Then I got a small block of wood and placed it on the pinion. Couple of light taps with the hammer and the pinion was out. Now, while inspecting the crush washer, it did not seem to be crushed at all. Again, since I have not seen a crushed crush sleeve before I am not sure what it looks like. But I assume it would be somewhat crushed? I had a brand new crush washer that I bought with a different kit so I compared the two. They seem to be the same height. Here is a picture of the new one (the one on the bag) and the used one side-by-side.
tempImageAOOy5k.jpg

I am not sure what to make of this. I think someone tried to install or rebuild the diff and gave up half way through.

Regardless, it has been a fun project so far and I am learning a lot.

What do the experts think? Am I on the right track with this?
That gear pattern does not look good at all.
Drive-Side way to low (towards the toe of the gear)
Coast side is way too high (towards the top/crown of the gear.
No way that would not make noise.
When you are rolling pattern, hold pinion with your hand or a rag wrapped around pinion to give some resistance. Then take a 13/16 box end wrench on one of the ring gear bolts and roll the pattern that way.
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