[Beery]

so, i'll be getting around to putting my lockers in soon and I've ordered some solid pinion spacers from lowrange offroad to put in while its apart. I'm having some second thoughts because the spacer is machined slightly shorter and you use shims to get the correct bearing preload. I think Ideally you would figure out what length spacer you need and get it machined exactly so no shims are needed.

My concern is that maybe the shims could become a weak point? I haven't received them yet so I'm not sure on thickness but getting the bearing preload right would require some pretty fine adjustment.

I can't find any info on anyone running this particular spacer in a sierra, i think they're the only spacer available off the shelf but I don't think they have been available for long. It's pretty common in the Toyota scene to fit a spacer and the general consensus seems to get a spacer machined to the exact size but I haven't seen any proof of a shim failing.

Maybe I'm over thinking it and it will be fine, I'm sure a lot of people are running crush tubes and have never had a problem but i'd like to improve on that aspect if I can. Would shims be stronger than a crush tube? Keep in mind my car is currently 4.9 transfer geared, only 29inch tyres and the standard 1.3, it's hardly stressed compared to a lot of combos on here.

Keen to hear your thoughts.

[tanshi]

You are over thinking it. Shims will be fine. I run solid spacers and shims in my ultra4 buggy and im alot harder on them than you will ever manage in a zook.

Shils are not going to collapse with the pressure of a diff.

[Brenno]

I run 4.9s with a turbo 1.8 on a solid spacer, nil issues. They are great.

[Beery]

I'm pretty good at overthinking stuff tanshi... I'd heard some stories of 80 series diffs spitting shims but again, no proof. That gives me a lot of confidence though, I highly doubt I'll have issues, I'm pretty easy going behind the wheel.

Brenno - is that with a shim type? or did you have it machined?

[Brenno]

Shim mate, would be very hard to machine it exactly and get it right

[Beery]

sweet. yea there's a bit of time involved for sure.

[Beery]

Bumping this thread because my brain hurts again and I need some answers... if someone can give them.

This all came about when a few of us hijacked Darren's (ADD engineering) post about a diff rebuild kit over on thee Facebooks.

I've been thinking about how a solid pinion spacer can prevent a loose pinion ever since I installed mine. The general reasoning for installing one is that you eliminate the crush tube that supposedly can crush MORE under high loads, therefore loosing preload on the bearings, causing a loose pinion, then pinion/crown wheel soup appears in the bottom of your housing.

But, I can't work out how a crush tube can crush more - I don't think it's under any load when the diff is in a high stress situation (or any situation really), I think the only "load" on it, is the compression caused by the pinion nut squeezing the the two bearings together and the spacer/crush tube is caught in the middle. I think it's main purpose is to allow sufficient torque on the pinion nut to 1: "clamp" the bearings together and prevent the outer bearings inner race (drive flange end) from spinning on the pinion, as it's quite a "loose" fit compared to the main bearing, presumably to aid installation and 2: Stop the pinion nut coming loose.

Here's a few of my reasonings: The spacer isn't actually required to set preload - theoretically, you could set the diff up without a spacer/crush tube at all. You would still be able to get the correct preload, it's just that the pinion nut wouldn't be very tight at all, which isn't good for the the reasons above.

How can it crush more? I can't see how it's under any load. For the tube to crush more, the two bearings would need to be "squeezed" together, which isn't a scenario that is possible - The pinion nut can't tighten itself more, and if one bearing is under pressure, nothing is acting against the other bearing to cause the spacer to crush.

Take the rear diff for example: under heavy acceleration the pinion is trying to push away from the crown wheel (towards the front of the car). Ultimately the pinion is connected to the driveshaft, that has a slip joint in it, meaning the spacer can't possibly be under pressure here so it can't crush - for instance, imagine if the main pinion bearing disappeared out of the diff. The pinion could literally be pulled out of the carrier (the gear end would hit the carrier housing or whatever, but hopefully you get the picture) Meaning that all that rearward pressure has to be on that bearing - If the pinion was able to apply force to the spacer, then this wouldn't be possible.

so I believe all the pressure is on the bearings, specifically the main pinion bearing (gear end) in this scenario (and the opposite when in reverse). The only way to end up with a loose pinion is if a bearing fails, distorts or is worn.

I'm not dissing solid spacers, I'd still choose one over a crush tube any day as they are re-useable, you can change a pinion seal without worrying about preload and they also allow more torque on the pinion nut but I'm not convinced they stop loose pinions, (yet) I think good bearings and proper diff setup are the key.

If anyone bothered to read all of that and made any sense of it, then give me your thoughts, I'm interested.

[fordem]

It makes sense to me, and my interest at this point is I'm considering a rear axle "re-build" - I might not get to more than replacing the wheel bearings, which is all I think it really needs, but also up for contemplation is a shave and an air locker, and if I'm going to go that far, then new bearings & seals are a given. I had the opportunity to watch a diff being rebuilt (by the same guy who would be doing mine if I have it done) and crushing that sleeve takes quite a bit of leverage, going to a reusable solid spacer, especially when it comes as one kit (from Low Range Off Road) sure looks like a lot less hassle.

Given what I witnessed, pinion flange clamped in a bench vice, 3/4" square drive, 24" long power bar on the pinion nut, along with another 24" or so of pipe, I'm estimating upwards of 300~400 lb-ft of torque were applied to crush that sleeve, and that was with the flange locked & immovable, which, to my mind, is not exactly a situation that you'll run into in the real world.

Maybe if you're constantly "hammering" on it, but, outside of competition, how often does that happen?

[Beery]

Yea, crush tubes don't exactly crush easily. From my experience, going to a solid spacer isn't any harder to setup compared to a crush tube, it's just more time consuming, but worth it for sure.

I don't think it matters if it's a competition environment or weekend wheeling, I'm not convinced it's the spacer that fails as I can't see how there's any "crushing" load on it during operation, it has to be a bearing in my mind. (Or the pinion nut loosening or something, but very unlikely)