SC axle boot replacement

[Otter74]

When doing pre-rally prep on my car the other week, I noticed that my left inner axle boot is tearing. Couldn’t deal with it then, but no problem, I’ll do it this summer.

I’ve looked over some of the archived posts on this and I am a little puzzled by the boot/flange options. The Porsche option is as expected, and what is on the car. The GKN/etc option is…not. I am not quite sure how a stamped flange that I see is going to bolt up to the stub axle the way the original one does. I’m naturally inclined towards Porsche parts for a part like this, but it’s 4x the cost. I would think I could just replace the boot, put a new Oetiker clamp on it and replace the gasket on the flange. But I don’t see a boot listed as available. I’d appreciate any beta that y’all may have. Why is it even necessary to replace the flange?

[REVerend]

Under the car looking at things a couple weeks ago it was clear that my boots would need replacing at some point, they might last another couple years or they could come apart at some inopportune moment on a road trip.

Looking around at the options I ordered up a pair of the GKN axles from Rock Auto for $207 each. Haven’t had a chance to actually do anything with them but it seemed worth a try. I replaced the CV axle shafts on one of my other cars last year and it was surprisingly straightforward but I look forward to seeing what info you gather here.

[Otter74]

An entire GKN axle for $207 is appealing compared to $174+S/H for a Porsche boot and flange, and it's certainly an easy replacement (bolt out / bolt in), but I'd rather just replace the boot for boot prices since that's all that's broken.

[REVerend]

Another way to look at is that you are buying a boots with a bunch of extra parts thrown in for $33 more. Just use the boot and leave the rest of the GKN cv/axle assembly on the shelf for if/when you need it.

My CV joints seem good but I don’t wanna mess with them for a while so I’m just gonna put the GKNs on for now and replace the boots and further inspect the CVs at my leisure. Doubtful I will swap them back afterwards just for the sake of doing it but it’s nice to have the original parts/spares around.

[REVerend]

Also FWIW here are the boots on either end of the GKN axle… I had seen a very old thread here that was saying the boots were not as heavy as the originals. It’s difficult to really compare as I am laying on the garage floor and just reaching under to feel the boot. Plus mine are hard from age but they feel roughly equivalent. I had kinda been concerned about that but I’m reasonably satisfied that they will hold up.

[Jonny042]

The new style boots don't have the heavy inner steel plate with the relief for the gasket machined in. Instead, the metal flange slips over the OD of the joint and seals the grease in that way. The bumps between the bolt holes in the flange ensure the balls can move through the entire range of motion.

This is more typical of a modern GKN application. My Touareg comes to mind. The metal boot flange is a vey tight fit over the CV joint OD.

You can (or maybe, should) use a shorter bolt with the new style boot and metal flange.

Originally Posted by Jonny042

I've been busy with a few things of late, not project or car related. In the meantime, I've been trying to make sure something is happening on the project, even if it's a little thing, every single day.

More often than not it means buying a part, or researching something when I have a few minutes to spare.

Not so long ago I had four brand new GKN CV joints sent straight from Pelican Parts to a race shop that offers CV lightening services. The results were impressive:




Not a bad start, at least. This is a small part of a larger and heavier assembly - I have found a place to make axles to my specification at a reasonable cost, so combining hollow axles, the lightened CV joints, and a few other tricks I have up my sleeve will result in a total of 10 pounds saved off the axle assemblies!

When it comes to shaving off weight, 10 pounds is a pretty big deal, so I'm happy with that.

[REVerend]

Originally Posted by Jonny042

The new style boots don't have the heavy inner steel plate with the relief for the gasket machined in. Instead, the metal flange slips over the OD of the joint and seals the grease in that way. The bumps between the bolt holes in the flange ensure the balls can move through the entire range of motion.

This is more typical of a modern GKN application. My Touareg comes to mind. The metal boot flange is a vey tight fit over the CV joint OD.

You can (or maybe, should) use a shorter bolt with the new style boot and metal flange.

That CV lightening is very interesting as they seem a bit on the heavy side. Is the shop in the US or Canada? How much to get them slimmed down?

[Jonny042]

I realize I copied the wrong post - here are the weight savings for the boot replacement and CV lightening separately:

Originally Posted by Jonny042

Yes. Note that the modern version of the CV boot flange that Caps the CV joint does not have the thick steel plate with the gasket relief, and is much lighter. So contributes greatly to the lightness of the assembly.

Joint only:





Boot only:

[Jonny042]

Originally Posted by REVerend

That CV lightening is very interesting as they seem a bit on the heavy side. Is the shop in the US or Canada? How much to get them slimmed down?

It's a place in WI, and to remove the 12oz or so from each CV is $100.00.

https://www.twodogg.com/

IMO for most cars it's not worthwhile, but I'm building a slightly over-the-top Hot Rod with a focus on light weight.

The target weight is 780kg, so it's not going to happen unless I chase down every possible gram (within reason of course!).

I'd be interested to know the weight of that whole replacement axle assembly, if you have a postage scale... the pelican parts listing says 13.8lbs which does seem pretty hefty, but could include bolts and packaging so could be high.

The reason I'm so curious, is the replacement axle shaft looks different than original, and there's a chance (however slight) that it's not solid:



I do have a place lined up to make hollow axles to my design which is the current plan but it's not a cheap plan.

[REVerend]

I don’t have a postage scale handy this weekend but will try and remember to do it next week. Just based on the feel though I would say 13lbs is about right.

That price doesn’t seem bad at all, the biggest hassle would be shipping it up there. But for my car at the present there are a lot of other lower hanging fruit to lose weight.

It’s an interesting exercise to get the car as light as possible. I remember Doug Hayashi talking about prepping his Acura NSX for the track and going through it all cutting excess length off of bolts and the like. Think he dropped something like 75lbs jsut from that.

[Otter74]

So does the new-style (GKN) axle boot flange slip over the flange on the transmission stub axle, rather than butting up to it like the Porsche flange? This is the part I’m having a hard time visualizing. If so, the installed length of the boot assembly would be longer and the need for shorter Allen head bolts would make sense.

[REVerend]

Originally Posted by Otter74

So does the new-style (GKN) axle boot flange slip over the flange on the transmission stub axle, rather than butting up to it like the Porsche flange? This is the part I’m having a hard time visualizing. If so, the installed length of the boot assembly would be longer and the need for shorter Allen head bolts would make sense.

I won’t get around to messing with mine for at least a month or two and never have had that portion of my car apart to know.

[Trippyloaf]

Empi has a solid flange boot kit available if you are looking for that design and don’t want to pay the Porsche tax. They are on eBay for around $34. I installed a set a couple years ago and they have held up fine.

[Otter74]

Thanks! Wouldn’t have thought to check for that.