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Looking for a 25mm or 28mm drive shaft as I recently broke mine.
I'm going to replace the TT bearings as well so the drive shaft diameter doesn't matter at this point.
Thanks,
Mike
Because of the deterioration and resulting increased twisting of torque tube shafts, I have brand new 300M torque tube shafts for $695.00.
BTW....the 28mm shafts should not be used. All of the "twist" is concentrated right at the area where the smaller area for the splines meets the 28mm section. Not very sound engineering.
Yes, I've heard the 28mm ones are not a very good design, so I'm hoping someone has the 25mm version. I know you've done a really good job in engineering the 300M shaft, and if I could afford it, I'd bite - its just not in my budget at the moment
Agree with Greg (Gee! there's a shock!). (And I saved the tail-end of the twisted mess to prove it).
No-one had the new lemony-fresh really cool replacement options when I did mine.
So, I retro-graded to the obvious choice without the tapers......
Thanks to our vendor and expert - base we now have some really interesting options that I would have used...but alas....
Constantine also has new driveshafts in a variety of materials available if your'e looking at a new option.
Myles
Thanks Myles!
Yes we also engineered new 928 5-speed and 25mm auto drive shafts from a cold finished/heat treated material which is stronger than stock, but not 300M. They are zinc coated for corrosion prevention. We did this about ten years ago since we saw the need for new drive shafts from the research we had done for our 928 Super Bearing lines.
Currently we only have one new 25mm auto drive shaft left.
We are ordering more this week since we are now getting more calls for each.
Prices for each were $350.00, but will have to re-check the pricing after our order since we expect the prices to have risen a bit.
Also engineered new 944 5-speed drive shafts ($450.00 each) for the 944 crowd which sell a bit faster than the 928 drive shafts. Go figure...
Also agree with Greg about the 28mm drive shafts. Yes there are still thousands of 928 automatics driving around with the newer 28mm drive shafts. But they shear more often than the 25mm versions, at least from our experiences serving our customers.
I bought Constantine's Super Bearrings a few years ago, thinking that my '87 S4 Auto would carry the 28 mm version of the shaft. Recently, after removing the Torque Tube from the car, I discovered my car was fitted with a 25 mm shaft.
Thinking switching the bearrings for 25 mm ones would be too costly, I sourced a 28 mm shaft with a local parts shop. That shaft was covered with some surface rust, so I had it blasted and now it looks like brand new (albeit with some small surface ruist spots again):
Should I try to get the old 25 mm shaft back and go for a new set of 25 bearrings, or is the 28 mm not thát bad? I.e. are all GT's and GTS's badly engineered in respect to the drive shaft?
If I decide to use this shaft afterall, what should I do to it to prevent further rust? Put some WD40 on it?
I bought Constantine's Super Bearrings a few years ago, thinking that my '87 S4 Auto would carry the 28 mm version of the shaft. Recently, after removing the Torque Tube from the car, I discovered my car was fitted with a 25 mm shaft.
Thinking switching the bearrings for 25 mm ones would be too costly, I sourced a 28 mm shaft with a local parts shop. That shaft was covered with some surface rust, so I had it blasted and now it looks like brand new (albeit with some small surface ruist spots again):
Should I try to get the old 25 mm shaft back and go for a new set of 25 bearrings, or is the 28 mm not thát bad? I.e. are all GT's and GTS's badly engineered in respect to the drive shaft?
If I decide to use this shaft afterall, what should I do to it to prevent further rust? Put some WD40 on it?
Thanks for any advice.....
I would mask off the splined areas and either paint it or have it powdercoated. If you use a paint like Eastwood's Rust Encapsulator, it actually bonds to the light rust in your photo better than it will to clean metal and has neutralizing properties in it so tge rust doesn't spread. If you end up reblasting them, brush them with a solution of Eastwood's Metal Wash then use a product like their Chassis Black.
The splined areas will be greased so rust won't form there and you don't want those painted or coated where it could effect the fit.
I bought Constantine's Super Bearrings a few years ago, thinking that my '87 S4 Auto would carry the 28 mm version of the shaft. Recently, after removing the Torque Tube from the car, I discovered my car was fitted with a 25 mm shaft.
Thinking switching the bearrings for 25 mm ones would be too costly, I sourced a 28 mm shaft with a local parts shop. That shaft was covered with some surface rust, so I had it blasted and now it looks like brand new (albeit with some small surface ruist spots again):
Should I try to get the old 25 mm shaft back and go for a new set of 25 bearrings, or is the 28 mm not thát bad? I.e. are all GT's and GTS's badly engineered in respect to the drive shaft?
If I decide to use this shaft afterall, what should I do to it to prevent further rust? Put some WD40 on it?
Thanks for any advice.....
I'm guessing that Constantine would exchange the 28mm bearings for the 25mm variety. That would allow you to use the better 25mm shaft, which would be way smarter/better.
That the 28mm drive shafts fail at the base of the taper is undeniable but as to why they fail is a moot point. The taper can presumably act as a a stress raiser but I am damn sure Porsche engineers would have understood this dynamic. As an owner who experienced such failure back in 1999 on a shaft that had covered 84k km all I can say is that at the time I was outraged by the lack of interest shown by Porsche. Of course in those days I had a clamp that was slipping but since I took the Loctite route to salvation nothing has moved and nothing has failed and my current shaft has some 160k km on it [approx 100k miles]. Of course for all I know it may fail next time out albeit I think that is highly unlikely.
What I did note at the time [when my flex plate clamp was slipping] was that I could tell immediately that it had migrated because of an induced annoying vibration at exactly 3050 rpm. I have pretty much convinced myself that the slippage and resulting compression load on the shaft lead to fatigue failure. The $64 million question is whether other shaft failures were linked to such slippage [known or unknown].
Whereas the 25mm shaft appears to be the safer option, now that we have options to secure the flexplate clamp and presumably most examples left are now well sorted, one wonders if these things are still snapping at the same frequency on 28mm shafts or whether this never happens on examples that are well and truly clamped.. I can only comment on a sample frequency of one and that is not relevant but it would be interesting to hear if any owners have had shaft failures on shafts that were known to have no clamp slippage issues.
I would mask off the splined areas and either paint it or have it powdercoated. If you use a paint like Eastwood's Rust Encapsulator, it actually bonds to the light rust in your photo better than it will to clean metal and has neutralizing properties in it so tge rust doesn't spread. If you end up reblasting them, brush them with a solution of Eastwood's Metal Wash then use a product like their Chassis Black.
The splined areas will be greased so rust won't form there and you don't want those painted or coated where it could effect the fit.
Thanks for your asvise, Petza. I think powdercoating the drive shaft while masking off the splined areas might be the best option....
I'm guessing that Constantine would exchange the 28mm bearings for the 25mm variety. That would allow you to use the better 25mm shaft, which would be way smarter/better.
Do it once, do it right.
Thanks for your input, Greg, I truly get your point. And without additional options I would probably follow your lead right away. I'm not an engineer, so I have to seek advice and then follow my guts. FredR's view that the problem with the 28 mm shafts could partially be tributed to the shaft movemend and therefor could be seen in a different light when Constantine's clamp is used (which I luckily also bought) makes that my 'gut' tells me to go for the 28 mm shaft and bearings.
If ever the shaft breaks I will humbly admit my bad judgement and buy you a well deserved beer whenever you visit my continent...:-)
07-21-2015, 07:11 PM
WTB : 25mm or 28mm Drive Shaft for late model S4
