True Trac into M80

[Jolls]

Hi Team
I just purchased a VY SS ute and the diff supplied is an empty M80 case with an Eaton True Trac with Dana 3.9s new in a box. I have never done a diff setup before; but I do have the required presses and tools to do the job.

I am tossing up sending it off to get the job done professionally and using it as a learning experience. Any advice from those that have done this before?

I do have a good diff out of my written off VZ (hit a roo) that I can use in the interim so time is not a huge issue to me.

Cheers n Beers
Jolls

 

[Immortality]

It's a time consuming process.

Setting the backlash isn't that hard as the adjustment is threaded. It's setting the pinion height that can be a pain. On the M80 they put the shim under the pinion bearing tapered race that is pressed into the diff housing.

I've done one but I didn't have the correct pinion shims so the pattern is a little deep on the crown wheel and the diff is a little noisy.

You also need to make an adapter so you can hold the drive shaft coupling on the pinion so you can do up the pinion nut, it takes a decent amount of torque to get that crush sleeve to move. I used a 600mm power bar. As it tightens down you also need to keep spinning the pinion so the bearing doesn't bind up as the pre-load comes one.

 

[Jolls]

It's a time consuming process.

Setting the backlash isn't that hard as the adjustment is threaded. It's setting the pinion height that can be a pain. On the M80 they put the shim under the pinion bearing tapered race that is pressed into the diff housing.

I've done one but I didn't have the correct pinion shims so the pattern is a little deep on the crown wheel and the diff is a little noisy.

You also need to make an adapter so you can hold the drive shaft coupling on the pinion so you can do up the pinion nut, it takes a decent amount of torque to get that crush sleeve to move. I used a 600mm power bar. As it tightens down you also need to keep spinning the pinion so the bearing doesn't bind up as the pre-load comes one.

Thanks Immortality

So if I have it right there is no requirement for shims except under the pinion bearing. So it is a matter of best guess for pinion depth and then adjust based on the lap pattern. As I have a new pinion I can't rely on the shim that was already in there but it is probably a good place to start (if I can find it). Thanks for the tips I will keep researching.

Cheers n Beers
Jolls

 

[losh1971]

Thanks Immortality

So if I have it right there is no requirement for shims except under the pinion bearing. So it is a matter of best guess for pinion depth and then adjust based on the lap pattern. As I have a new pinion I can't rely on the shim that was already in there but it is probably a good place to start (if I can find it). Thanks for the tips I will keep researching.

Cheers n Beers
Jolls

Is there no shims on the carrier bearings, like I have seen on the two diffs I have disassembled?

 

[Immortality]

on the IRS diffs there is no need for shims under the carrier bearings because the hubs are threaded.

 

[losh1971]

on the IRS diffs there is no need for shims under the carrier bearings because the hubs are threaded.

My diff has a carrier bearing shim on each side of the housing. I thought the early IRS might have had them too.

 

[Jolls]

Is there no shims on the carrier bearings, like I have seen on the two diffs I have disassembled?

on the IRS diffs there is no need for shims under the carrier bearings because the hubs are threaded.

Immortality,
Thanks for the clarification. I will rat through the components in the milk crate tomorrow and see what is in there to start from. If I can locate the pinion shim I will give it a try and see how close we get and adjust from there.
Cheers

 

[Immortality]

Thanks Immortality

So if I have it right there is no requirement for shims except under the pinion bearing. So it is a matter of best guess for pinion depth and then adjust based on the lap pattern. As I have a new pinion I can't rely on the shim that was already in there but it is probably a good place to start (if I can find it). Thanks for the tips I will keep researching.

Cheers n Beers
Jolls

Does your pinion have a depth stamped on it?

My Motive gears set had a pinion depth written on the top of the pinion but I had a blond moment and didn't see an easy way to measure it so I just used the original shim that was under the pinion bearing race when I put the new bearings in.

What I have seen others do is either grind down the pinion bearing inner so it slips over the pinion and use that to set it all up as a sacrificial bearing and then do a final install with a fresh bearing or do the equivalent with the outer shell in the housing. A diff guy also suggested using a heat gun to warm up the housing before fitting the race into it so it goes in easier. I haven't tried that yet. I did machine up a bit of stock to snugly fit into the race to make it easier to press or punch it in. I also used the inner race from the old pinion bearing (with a cut down the side to release the tension) as spacer to press the new pinion bearing on.

 

[Immortality]

My diff has a carrier bearing shim on each side of the housing. I thought the early IRS might have had them too.

Got a pic, you've got me here.

I'll be honest, I put in a new truetac center so I just pressed the new bearings straight onto it. I don't remember seeing any shims on the old LSD centre that came out.

We are talking about the M80 (or m75/76/78) here.

 

[Jolls]

Does your pinion have a depth stamped on it?

My Motive gears set had a pinion depth written on the top of the pinion but I had a blond moment and didn't see an easy way to measure it so I just used the original shim that was under the pinion bearing race when I put the new bearings in.

What I have seen others do is either grind down the pinion bearing inner so it slips over the pinion and use that to set it all up as a sacrificial bearing and then do a final install with a fresh bearing or do the equivalent with the outer shell in the housing. A diff guy also suggested using a heat gun to warm up the housing before fitting the race into it so it goes in easier. I haven't tried that yet. I did machine up a bit of stock to snugly fit into the race to make it easier to press or punch it in. I also used the inner race from the old pinion bearing (with a cut down the side to release the tension) as spacer to press the new pinion bearing on.

Hold my beer - I'll be back!