993 4WD gearbox - magic solutions?
Discussion
As per porker recommended service schedule, I recently had the gearbox oil changed on my 993 turbo. It has now started making an irritating, whiney transmission noise, apparently related to a roller bearing supporting the shaft taking drive to the front wheels.
I have previously heard of 'happy' gearboxes becoming 'unhappy' and noisy following an oil change, presumably because of the shite that gets moved around when a new charge of oil gets dumped in. My indy is telling me that it's OK to drive, i.e. no risk of catastrophic failure, but that replacement of the bearing is a gearbox out job. He proposed sticking an additive in that might get rid of the problem.
Anyone else with a 993 4WD 'box had this problem and found miracle solutions (other than taking the whine out of the box and drinking it)?
I have previously heard of 'happy' gearboxes becoming 'unhappy' and noisy following an oil change, presumably because of the shite that gets moved around when a new charge of oil gets dumped in. My indy is telling me that it's OK to drive, i.e. no risk of catastrophic failure, but that replacement of the bearing is a gearbox out job. He proposed sticking an additive in that might get rid of the problem.
Anyone else with a 993 4WD 'box had this problem and found miracle solutions (other than taking the whine out of the box and drinking it)?
Marquis_Rex said:
How does it sound? Worse than an old Mini?
I'm having to deal with broken turbo charger bearing casings
and leaky cam cover gaskets.
I'm having to deal with broken turbo charger bearing casings
and leaky cam cover gaskets. Hi Rup
No, not as noisy as the old straight cut mini box on the Marcos, but it's an irritating noise at speed. Can be drowned out by music so no problem when I'm alone in the car.
How many miles as yours done to be developing issues with the turbos? Have you been using thin oil like 0W40 because that's a good way of developing leaks.
nel said:
Marquis_Rex said:
How does it sound? Worse than an old Mini?
I'm having to deal with broken turbo charger bearing casings and leaky cam cover gaskets.
I'm having to deal with broken turbo charger bearing casings
and leaky cam cover gaskets. Hi Rup
No, not as noisy as the old straight cut mini box on the Marcos, but it's an irritating noise at speed. Can be drowned out by music so no problem when I'm alone in the car.
How many miles as yours done to be developing issues with the turbos? Have you been using thin oil like 0W40 because that's a good way of developing leaks.
Hi Niels, 49,800 miles, almost 50 thousand.
There's no problem with the Turbos- they boost fine and work fine, but because I needed them off to get the cam copver gaskets changed, the dealer is being ultra finecky. I examined the Turbo and there's no leaks and the residue left by the hot gases seems to indicate they're in good condition. However the cast iron bearing housing (which only reaches about 2-300 degrees) and an 8mm thick cast iron casting has developed a minor crack. The German dealer is being typically perdantic and being an arse/covering their arses and saying everything needs changing
I work with a guy who used to work at Weissach and he said that the Turbos usually see much more action during durability testing. I can get a kit to get the Turbos rebuilt to replace the central section or change the whole lot. Luckily I have business relationship/contacts at Borg-Warner, so could get the whole units ALOT cheaper than even Gert from Carnewal can get- however it's annoying... [The other annoying thing is that 996 Turbos are chaper than 993 Turbos and K24s are chaper than K16s!)
The dealers betting is that nearly all Turbos on 993s this age will show similar signs. In my opinion its not something to worry about. I switched to thicker oil, and the leaking was minimised but not eliminated. Porsche seemed to develop the older cars thoroughly and fastiduously, then you have dealers who change everything for virtually no reason- it's no wonder older Porsches seem to have a reputation for longevity, it's not all through design
For reference for any other 993 turbo owners who have similar problems, my gearbox has now been repaired by my local independent. Fortunately, after taking engine and box out to get to it, he was right in his diagnosis. The shaft taking power to the front wheels is supported in the gearbox by a single race ball bearing alongside the viscous coupling. When this starts to go, there is a transmission whine that gradually gets worse over the next 1000 kms as the bearing deteriorates. I have the SKF bearing that he replaced; the inner race and ball bearings are visibly pitted and it "zings" like a bastard when you spin it.
A relatively standard problem in that he has done a few of these jobs on 993 turbos - in his opinion the use of a single race bearing is a bit on the light side and a double race design would have been more appropriate. Anyway, took the car out for a shakedown blast yesterday and all is well now, particularly as he did the periodic geometry set-up job again.
For info it's a bit like an RMS job in that the part replaced costs sod all (~30€
and you end up paying the labour for engine and box removal and reinstallation, so around £750 in my case. That was my xmas present sorted then....
Happy new year - sun is shining here so am off out for another blast on drier roads than yesterday.
A relatively standard problem in that he has done a few of these jobs on 993 turbos - in his opinion the use of a single race bearing is a bit on the light side and a double race design would have been more appropriate. Anyway, took the car out for a shakedown blast yesterday and all is well now, particularly as he did the periodic geometry set-up job again.
For info it's a bit like an RMS job in that the part replaced costs sod all (~30€
and you end up paying the labour for engine and box removal and reinstallation, so around £750 in my case. That was my xmas present sorted then.... Happy new year - sun is shining here so am off out for another blast on drier roads than yesterday.
silver993tt said:
so it's a good time and basically 'free' to get this bearing replaced during a clutch change?
Yep, though ask advice of your specialist I guess. All I can say is that if I'd known about this weakness, I'd have had the bearing done at the same time as the clutch. Hindsight is a wonderful thing....
Funny thing is that I've not read anything anywhere suggesting that this is a standard 993 turbo failing other than one general comment on here by a dealer (Sportscar & classic?) about 993 turbo gearbox bearing fragility - strange when most regular foibles are documented somewhere, so am only going on the experience of my specialist.
That's basically why I revived this thread and gave it closure - I searched various forums and found zip, so maybe in the future some other unfortunate will benefit from my xmas present!
Happy New Year Nel!
Thanks for the tips-knowledge. I didnt know about any of this!
Every car type has peculiarities.
With the 993 Turbo, Id say - check the cam cover gaskets,
the Turbos, (its almost certain that the middle cast iron bearing housing has cracks in it but IMO this isnt a big an issue as dealers and pedants make out). The bearing housing of the Turbos reach about 200 to 300 degrees C and are an 8mm thick casting. Me, like an idiot, listened to my main dealer and changed both Turbos anyway, with the view to getting the old Turbos rebuild and sold at a later date. Examined/tested the old Turbos and theyre fine, they dont leak they dont use oil and are tight, so Ill rebuild them and sell them on later.
The cam cover gasket occurs because of the consderable heat, and the valve lash adjustment being hydraulic which means the gaskets never get changed. Again, its not a major deal as the engine will seep oil out but it IS a Turbo-and-manifolding off job to change em. The Gaskets get hardened.
Clutches go at about 50,000 miles.
Steering racks can weep-usually at the bellows but often dont need overhauling, happens more due to lack of use.
Needless to say Ive done all the above on my car to keep it mint, so if/when I sell my car ill expect top dollar, and the above maintainance are the things you should be looking out for and not just focusing on the milleage and number of owners.
I hope folks dont get paranoid after reading this post, none of these things are a big deal (except for what Nel posted perhaps) and probably wont lead to TVR-side-of-the-road antics, if you want a good 993 Turbo and considering the money good ones go for, its nice to know what youre looking forTo put into perspective, if I were buying a more "normal" old car like, say a BMW E34 535i, none of the abovesorts of issues would bother me and Id probably still run the car daily, but with 993 prides and joys it should be different.
Anyway Merry X mas and a Happy New year from Finland!
Thanks for the tips-knowledge. I didnt know about any of this!
Every car type has peculiarities.
With the 993 Turbo, Id say - check the cam cover gaskets,
the Turbos, (its almost certain that the middle cast iron bearing housing has cracks in it but IMO this isnt a big an issue as dealers and pedants make out). The bearing housing of the Turbos reach about 200 to 300 degrees C and are an 8mm thick casting. Me, like an idiot, listened to my main dealer and changed both Turbos anyway, with the view to getting the old Turbos rebuild and sold at a later date. Examined/tested the old Turbos and theyre fine, they dont leak they dont use oil and are tight, so Ill rebuild them and sell them on later.
The cam cover gasket occurs because of the consderable heat, and the valve lash adjustment being hydraulic which means the gaskets never get changed. Again, its not a major deal as the engine will seep oil out but it IS a Turbo-and-manifolding off job to change em. The Gaskets get hardened.
Clutches go at about 50,000 miles.
Steering racks can weep-usually at the bellows but often dont need overhauling, happens more due to lack of use.
Needless to say Ive done all the above on my car to keep it mint, so if/when I sell my car ill expect top dollar, and the above maintainance are the things you should be looking out for and not just focusing on the milleage and number of owners.
I hope folks dont get paranoid after reading this post, none of these things are a big deal (except for what Nel posted perhaps) and probably wont lead to TVR-side-of-the-road antics, if you want a good 993 Turbo and considering the money good ones go for, its nice to know what youre looking for
To put into perspective, if I were buying a more "normal" old car like, say a BMW E34 535i, none of the abovesorts of issues would bother me and Id probably still run the car daily, but with 993 prides and joys it should be different. Anyway Merry X mas and a Happy New year from Finland!
aceparts_com said:
I would also add to the list a clutch hydraulic accumulator...
Yep - replaced mine when the engine/box were out for the clutch.
On other question given the experience you guys have - when the geometry was done he said that one of the rear wheels was well out, hence some strange tyre wear that I'd noticed and slight on/off power direction change. He said that this is normal given the power and torque being put down as it puts huge squirm and stress into all the flexible mountings.
In particular, he suggested one way of keeping the geometry more precise for longer is to replace the round flexible supports connecting the rear axle to the body with solid aluminium mounts (presumably polybush options exist too). Any of you done this?
Hi Niels, yeah, I forgot about the alignment issues of the 993.
I didnt have any adverse tyre wear issues on the rear of my car, but I had excessive inner shoulder wear at the front, a bit too much understeer and "weird" feel on autobahns, so I got the tracking done and everything seems to be OK now.
I might get the bushing on the rear alloy arm done at a later date anyway. Does the whole aluminium rear arms have to be replaced as well as the bushes?
I didnt have any adverse tyre wear issues on the rear of my car, but I had excessive inner shoulder wear at the front, a bit too much understeer and "weird" feel on autobahns, so I got the tracking done and everything seems to be OK now.
I might get the bushing on the rear alloy arm done at a later date anyway. Does the whole aluminium rear arms have to be replaced as well as the bushes?
aceparts_com said:
I'm sure the solid subframe bushes is a RUF mod. You might want to crawl under your car and check the tightness of the LOWER SHOCK bolts - both of mine were so lose the rear wheels could be pulled 5mm in any direction.
Those would be www.ruf-automobile.de/content.php?seite=shop/produkte.php&details=252
And this looks to be another source: page 71 of the catalogue at www.smartracingproducts.com/rearaxle.htm. Looks to be $360 rather than €485 + 19% VAT.
phelix said:
And this looks to be another source: page 71 of the catalogue at www.smartracingproducts.com/rearaxle.htm. Looks to be $360 rather than €485 + 19% VAT.
Thanks for the link - that's looking more reasonable. The Ruf kit seemed alot of money for what you actually get. I did have a quick look for Powerflex/Polybush versions but couldn't find anything.
Will have to think about doing this as my specialist said that it greatly improves tracking precision without any real downside, i.e. the ride does not get significantly harsher as there are still all the flexible bushes in the suspension arm mountings.
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