Anyone did a diff rebuild?
 

Hi guys,

Got a quick diff rebuild question, was hoping someone has the experience to clarify this for me.

Going trough the manual you need special tools (obviously), and I am not planning in purchasing these if I don't absolutely need to (obviously :lol:).
The part that bothers me the most is SST 49 F027 001 and 49 0660 555 (see image).

https://cimg3.ibsrv.net/gimg/www.rx7...f407457dcd.jpg

You should measure pinion height with these tools, but I'm looking for an alternative.

Would the depth measurement on the pinion gear BEFORE removal be usable as the desired value for adjusting pinion depth on reassembly?

Thanks

kevin

Yeah, I did a rebuild some years ago. That SST is not necessary. Use your original pinion spacer. May I ask what you're doing?

Sure. Just ordered an LSD. So I am considering rebuilding the whole thing as its 200k km old.

Using the old spacer might not cut it when I renew those pinion bearings so I'd like to verify some measurements before final installation.

In answer to your original question, that SST is used to set pinion depth accurately from the start without using the trial and error method with ring gear marking compound.

New bearings will not change your current pinion depth. The current pinion spacer, whatever its thickness, was installed during assembly to account for variations in the diff housing during manufacture. However, you might want to use ring gear marking compound just to verify that you have the correct tooth contact pattern.

I've been putting this off, but since I'm finishing up on my rebuild, I have a couple questions here too. I've got (what I would consider) a fair amount of play at the outputs of my diff where the axels bolt on. I can wiggle the outputs about 3/16 or so on either side. There is also a little bit of slop that can be felt when starting from a stop, or coming a full stop by the rest of the drivetrain catching up to the backlash. Would this be more of a bearing issue, or is there something else I should look into before cracking this thing open. Diff is S4TII

Regarding the wiggle at the output shafts, it's probably due to your clutch plates being worn out. The clutch plates put pressure on the side gears forcing these gears to mesh with the spider gears. When the plates are worn, this whole assemble loosens up due excessive play between the side and spider gears. Mazda lists different thickness shims that can be used to tighten up the clutch plate pack. Excessive backlash is most likely due to worn bearings. There are three bearings on the pinion shaft and the bearings towards the front tend to wear out faster since they are more prone to oil starvation. So, it's probably a combination of all the above. Worn clutch plates, bearings and backlash/bearing preload being out of adjustment.

Thanks for the info. Sounds like an overhaul is in order.

The current spacer might very well be the one that is needed, but I wouldn't be surprised if new bearings do affect pinion depth. I've done multiple VW gearboxes (fwd), lets say I do diff bearing replacement, I always need to use a slightly different thickness of spacer. In that case to set the proper preload. So I am not 100% convinced that new bearings won't effect anything. Whether it be preload, or in this case, pinion depth.

So I prefer to take a measurement to be sure and change if needed, but I'm not quiet sure if the depth measurement in current state would be a usable value to refer to after reassembly.

Perhaps we are not on the same sheet of music here. The pinion spacer that I'm referring to is a large washer of predetermined thickness. Mazda sells 14 different thickness pinion spacers ranging in thickness from 3.08 to 3.47 mm. The pinion spacer is used to set the pinion depth. I think you are referring to the crush collar (https://www.atkinsrotary.com/store/R...ntial-Sleeves/) which should definitely be replaced any time the pinion gear is removed. The crush sleeve is what is used to set the pinion preload.

you seem to be off tune i.e. did you read his post? Or at least his position was clear to me as was yours.

seems like the new LSD might be a factor because if it changes the ring gear position even slightly then this will impact pinion gear tooth engagement position

because additionally the factory service manual literature he posted states to use the original washer with the service tool. So why would you do all of that if just throwing it together with the original spacing washer is guaranteed to be dead nuts on? Wouldn’t it suggest otherwise :dunno: or at least it may just depend on a variety of factors.

so the suggestion to measure it seems reasonable, guess the OP has to decide on whether to chance guessing at it and possibly needing to buy one or more new crush collars trying to get it right if it’s off.

you might as well. the housing got machined and fitted with the spacer, so if you also reuse the original gear it should end up the same as when you started.

Thanks for the replies so far guys.

I'll try to measure the pinion depth before assembling first. I can always start over if teeth engagement is off.

LSD should be in with 3 weeks or so, not sure when I pull the diff though