mar-tacking shafts

[callum]

going to do this at the weekend whilst i have the front hub apart as those snap rings are a pain in the backside.

anyone done this and got any tips, measurements etc? mine doesn't have a locker at the front so i think the splines are much shorter (long shaft). have gone through write ups on the internet but would appreciate any first hand feedback.

thanks

callum

 

[Jon Wildsmith]

I've done it but it was a few years ago now so the details are a bit vague. I used tape around the splines to gauge placement of the weld and ground the weld back to flush with the shaft so it wouldn't snag the oil seal. Has been a success so far.

 

[Chris]

OK OK, looks like I shall have to go first and ask what many others are probably thinking. What hell is mar tacking and why haven't I got one?

Something to do with snap rings on the end of a front drive shaft of an 80 - I think I get. Replacing it with weld? Err nope lost me at that point. It this inside the CV or on the hub splines or in the diff end? Snagging the oil seal suggests that this in on the driven end.

Chris

 

[Jon Wildsmith]

You know the drive shafts can be a pain to remove from the CV's because of the snap ring that ends up inside the CV, especially if you're doing a field repair. Without the snap ring the drive shaft would come out the CV, if not completely then far enough to strip splines under load. A mar tack is just some blobs of weld in the shaft splines at the diff end, positioned so the shaft goes into the diff the correct amount and no further. Then you can do away with the snap ring in the CV and the parts just pull apart.

 

[Gav Peter]

I have to say that I wasn't looking forward to seperating the CVs from the shaft last week & then I tried the method outlined by SUVSteve way back when he did his superb pictorial writeup of the front axle service... Gravity vs the clip!!!

The problem was not having a bit of metal tube like his scaffold pole...

However, I did have a couple of peices of metal box section which when spaces apart on blocks of wood did the job superbly.

Yes, if you were in the field then it might be more tricky but if I think on, I might just make up a square plate with an 'ole in it to carry in the back of the truck just in case.

 

[Jon Wildsmith]

I have had CV's that came apart easily and also seperated a few CV's that would never come apart with gravity and could only be seperated by enough force in a puller to destroy the shaft splines or slicing the CV up and they have been a mixture of OEM and Milner parts with no trend i.e. OEM is not always easy to seperate.

 

[Chris]

That's pure genius! Great for doing hub rebuilds too I guess. Much better to be able to put the shaft and CV in separately.

Hmm, I'll watch this this space.

C

 

[Scott]

I believe that JV does this to most, if not all 80's, when he's replacing the CV's. I know he did it to mine when we rebuilt the front axle.

 

[Julian Voelcker]

Very true Scott

I find most 3rd party CVs to be complete sods to separate from the halfshafts. If the old scaffolding pipe and gravity trick doesn't work within a couple of goes just give up because you will just end up messing up the halfshaft.

If the CVs are to be replaced we usually end up slicing them off with an angle grinder.

As for the Martack, it was originally thought of by the guys at Marlin Crawler in the states who build LC based rock crawlers. The theory is that the split pin in the CV is to stop the half shaft sliding into the diff so instead you put a couple of spots of weld on the splines of the half shaft (you can generally see the wear point where the shaft sits in the diff) to stop if from sliding into the diff.

We put a small spot of weld on either side of the shaft and then grind back with a flap wheel so that there are no sharp edges to snag on the inner axle seals.

It's well worth doing with 3rd party CVs making things a lot easier when you come to doing a re-pack.

 

[callum]

it goes without saying that this thread is useless without pics, so that being the case, here are some pictures.

I measured many times, moved an old drive flange into place to act as a barrier and then put a blob of weld in the splines. the flange was hammered off and the weld filed down flush and that was about it. i've checked the shaft and it seems to make the seal sit on the correct part of the shaft and of course it can't go in any further.

I've included a picture of why i did this, namely the knackered bits of spline from removing the old cv star very forcefully. Suffice to say i did not want to have to do that again.

some sources reckoned 1.5" along the spines for the tack, another 1 3/8". I ended up with 1 15/32", which you can see in the pics is 37mm for those of us who are not from the 19th century.

Whilst that was getting done, i dismantled my cv and sent the bell to a machine shop for them to put a 6mm hole right down the middle and make a recess and threaded bit in the top for me to add a grease nipple. Rather than bunging grease in the side of the swivel, i can now pump it right into the middle of the cv, which makes things a bit less messy.

I have some plastic knuckle wiper things coming from longfield, so i'll post some piccies when they arrive and that should finish off a bit of an unscheduled axle service.

 

[Gav Peter]

Neat idea on the grease nipple Cal