DIY - Differential and Ring & Pinion Swap

[kodyo]

Originally Posted by ChrisD

Finally got round to having a go at this today and the first issue I've come up against is after opening up the diff case and removing the two covers that go over the bearings on each side, I can't get the diff itself out of the case... it just won't budge. In the OP's guide he just says "with a bit of work it will come out" but me and a few friends have all tried pulling it and wiggling it as much as we can and it won't budge.

So then we thought maybe its just the fact that the pinion gear is still meshed with the ring gear and that's stopping it all from moving because we haven't undone the pinion shaft nut. But I don't see any mention of undoing that pinion nut before taking the diff out of the housing in the OP's guide, and I was kind of trying to avoid doing anything to the pinion because I'm only swapping the diff and not changing ring/pinion for final drive change. Plus the toyota service manual seems to suggest that pinion nut needs an insane amount of torque, something like 280 lbs-ft.

So yeah, can anyone clarify if you need to remove the pinion nut (or anything else other than the two bearing caps) before you can pull the diff itself out of the housing?

You don't have to remove the pinion nut to take the diff out. If you were to undo the pinion nut, you would have goofed up because the torque on that nut is crucial to setting the bearing preload via the crush washer and it's kind of a pain to reset.

The manual says to tighten the pinion nut to 74 ft-lbf and check the prevailing torque it takes to turn the gears via the pinion to confirm preload. Then adjust UP TO 249 ft-lbf until it is in the proper range. For used pinion bearing and used differential case bearings, the prevailing torque should be 13.3-22.9 in-lbf per the official service manual if the bearings are preloaded correctly.

As far as removing the differential, the way I did it is a little sketchy, but works if you are careful. The teeth are meshed and must unmesh for you to remove the differential. That, combined with the high friction of the shims that preload case bearings, makes this difficult.
1) Remove the cradles that hold the bearing races in place.
2) Mark the left/right bearing races/shims so you can identify them later. When you pull the diff out, they will likely fall off and you need to put them back in the same place you found them.
3) Get a soft piece of metal (read "aluminum") or a piece of rubber and place it on the flat seal surface where the adhesive gasket sits on the differential case. This will be your fulcrum location and you need to protect it from getting scarred.
4) Take a crow bar or other stiff piece of metal and fit it behind the round part of the differential and try to pry it out. You can also try to hit it with a hammer or find another solid shoulder on the diff to work against (I vaguely remember prying in the gap between the diff and ring gear, but this is risky as it may chip one of the teeth on the gear). You may also be able to work the diff from both sides to rock it forward and back until it works free (you would be working it in the same plane that the ring gear runs in. i.e. if the ring gear is a circle, work the diff in the direction this circle is drawn on, not in the direction of the case bearings).

Alternatively, you may be able to fit a rope behind the circular part of the diff and pull it straight out while tapping the diff with a rubber mallet.

You'll have to be creative, but this should hopefully help.

[ChrisD]

Originally Posted by kodyo

You don't have to remove the pinion nut to take the diff out. If you were to undo the pinion nut, you would have goofed up because the torque on that nut is crucial to setting the bearing preload via the crush washer and it's kind of a pain to reset.
....

Thanks for the explanation, I'll give that a go tomorrow.

Yeah I was hoping we would not have to remove the pinion nut or change the preload on it, as we're just replacing the diff and not replacing the pinion gear or ring gear (existing ring gear will be swapped onto the new diff). Is that right, or will we still need to change the preload on the pinion once the new diff is in? I'll measure the torque on it at the moment and check it once the new diff is in to be sure, but in theory will we probably be ok with leaving the pinion alone?

All of the guides I can find seem to assume you are taking the pinion out as well, so I'm just trying to understand exactly which bits we need to do when we're only replacing the diff and not changing final drive. I'm assuming we will still need to get some different size shims for each side of the diff where the axles and bearings sit, but hoping to avoid doing anything with shims on the pinion end.

[MisterSheep]

wow.

Just read through this whole DIY. I don't plan on doing this modification but I still like to read up on these to just see what steps are needed. Lots of work was put into this and would like to thank you for it!

[kodyo]

Originally Posted by ChrisD

Thanks for the explanation, I'll give that a go tomorrow.

Yeah I was hoping we would not have to remove the pinion nut or change the preload on it, as we're just replacing the diff and not replacing the pinion gear or ring gear (existing ring gear will be swapped onto the new diff). Is that right, or will we still need to change the preload on the pinion once the new diff is in? I'll measure the torque on it at the moment and check it once the new diff is in to be sure, but in theory will we probably be ok with leaving the pinion alone?

All of the guides I can find seem to assume you are taking the pinion out as well, so I'm just trying to understand exactly which bits we need to do when we're only replacing the diff and not changing final drive. I'm assuming we will still need to get some different size shims for each side of the diff where the axles and bearings sit, but hoping to avoid doing anything with shims on the pinion end.

You won't need to touch anything on the pinion for any reason. You'll want to measure backlash and gear meshing prior to removing old diff then try to match when you put new diff in. This should only involve adjusting the side shims on the new diff to get proper preload and ideally match the backlash as closely as possible as already worn in gears.

[rx3]

In my case I could reuse the old shims as the backlash was correct and this despite the fact that I changed the pinion, ring gear, differential and all the bearings and the pinion depth even needed to be changed by factor of approximately 3 (compared to the original one). On top of it I was using an old differential housing from a Lexus IS300.

So, it'd be surprised if you needed different shims if you just swapped the differential.

[rx3]

As far as getting the differential out:

I was simply using a brass drift pin and a hammer to drive the shims out and then the differential was dropping right out of its housing.
[ame="http://www.amazon.com/Tool-Aid-14270-3-Piece-Drift/dp/B0014DIK36"]Amazon.com: S&G Tool Aid 14270 3-Piece Drift Pin Set, Brass: Automotive [/ame]


(And removed the side shaft seals beforehand in order to reach the shims with the drift pin).

[ChrisD]

OK so we've hit a bit of a problem... the original shims don't fit with the new diff in and Toyota don't sell any small enough to make it fit!

We got the new diff in and tried the original shims, of course they didn't fit (too big) so we pushed the diff as far to one side as it would go and measure the total distance that the shims would need to cover (with feeler gauges). It was 4.4mm, so we're assuming ideally we need 2.2mm shims on each side but the smallest shim toyota make is 2.5mm.

Has anyone else encountered this problem? I'm struggling to find anywhere selling diff shims online, especially for this car (but not sure how vehicle specific they are really).

[rx3]

I've installed an OS Giken differential and could even reuse the old shims.

I'd be surprised if the bearing locations would be different on any other differential - especially since this differential was already applied in Lexus and possibly Supra models. Sorry if this sounds too obvious, but have you made sure that the new bearings were pressed all the way to the stop?

[ChrisD]

Originally Posted by rx3

I've installed an OS Giken differential and could even reuse the old shims.

I'd be surprised if the bearing locations would be different on any other differential - especially since this differential was already applied in Lexus and possibly Supra models. Sorry if this sounds too obvious, but have you made sure that the new bearings were pressed all the way to the stop?

That's what I'm thinking, that the bearings might not be on properly, as there is a small gap. But we pressed them on with 3 tonnes of pressure on a proper bearing press (using something that only contacted the inner race of the bearing, not the diff itself) and they wouldn't budge any further after about half a tonne of pressure. I think if we carried on past 3 tonnes it would have just bent something. These are brand new bearings from Toyota. Did you have to do anything weird to get your bearings to seat all the way down?

[rx3]

No, but initially I was heating the bearing to about 100 C, but I don't think that would have been necessary. I was using a 12 ton press to press the bearing onto the differential but don't know what the actual force may have been (it was less than what the pinion bearing needed). In any case, I don't think you could do any harm to the bearing as long as you only push on its inner ring.

[ChrisD]

We got the new diff installed in the end

I got this reply from Kaaz (the makers of my diff):

Most GT86 installs done here required total shim gap of over 5mm.
Normally about 5.3~5.8mm total gap space.
So if you only have 4.4mm, this gap in the bearing is probably causing the shim
fitment issue.

So we had another look and it turned out the reason the bearings weren't going on far enough is because the thing we were using to sit between the press and the inner race was not quite the exact right size for it, despite what we originally thought. It would push it down most of the way but then get caught on the tapered edge of the diff that sits inside the bearing. Once we realised that we found something else and they slid on all the way pretty easy.

Then we put the original shims in and measured backlash etc and all seemed perfectly within spec. So we got it all back on the car and so far so good! There's a very noticeable clunking sound on tight slow turns but apparently that is normal (though its hard to know if it should be quite this loud and noticeable) but no whining sound when driving at any speed at all.

One question I do have is how did anyone else torque the bolts on the drive shaft up to the right torque spec (the 4 bolts that hold the drive shaft to the pinion flange on the diff) ? We could barely get a spanner in there let alone a socket with a torque wrench on it. So we just did them as tight as we possibly could, but always wary of not doing things up to the right torque spec.

[rx3]

I'm glad you fixed it.

I wouldn't worry about that clunking. I have that occasional clunking at low speeds too - even though they said that the OS Giken diff would not clunk.

I also didn't have the proper tools for torquing the driveshaft.
What's important is that both mating surfaces are clean (otherwise you'll encounter some vibration at higher speeds.)

[BRZ RN]

great amount of detail. i got no one to help me with an install like this, i'll just hustle at work and let the shop do it for me.
I got a kaaz 1.5 way sitting in my barn. i'd throw in a DDS axle aswell.

[gpvecchi]

Sorry to re-up, I have to replace final drive in my new car (so I'll not change the diff bearings). If I understand, as I'll use a new standard crush spacer, I'll just have to adjust pinion preload using factory manual, so I'll need no shims. And I'll not need shims for diff, as I'll not replace bearing, is this correct?
Thanks!