GTS reverse gear B3 clutch replacement DIY
01-16-2015, 08:26 PM
#17
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When my reverse went on my GTS at 150k miles I now know I made the right decision and shipped it to Greg Brown - you are a master Schocki, and even with your pictures, I would not want to even start that job.
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
01-27-2015, 08:25 PM
#22
Nordschleife Master
Schocki, THANK YOU for taking the time to write up your procedure.
This is going to become an increasing issue for auto 928's, with failures of the B3 band with the resulting delay/failure to achieve reverse gear.
Empirical evidence suggests a lifetime of 150-200k miles, at which point this job needs to happen (and probably replace the other bands/clutches at the same time). Of course, that assumes good lubrication, and driver behaviour probably affects it too (like shifting into reverse while the car is rolling forwards slightly).
This is going to become an increasing issue for auto 928's, with failures of the B3 band with the resulting delay/failure to achieve reverse gear.
Empirical evidence suggests a lifetime of 150-200k miles, at which point this job needs to happen (and probably replace the other bands/clutches at the same time). Of course, that assumes good lubrication, and driver behaviour probably affects it too (like shifting into reverse while the car is rolling forwards slightly).
01-27-2015, 08:57 PM
#23
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Nice job!
One little caution I'd add.
When the B3 clutches wear out, the B3 piston needs to travel so far, that the springs which return that piston go into coil bind. Once this happens that spring retainer gets a tremendous amount of pressure exerted on it, which tries to "push" that retainer right over the circlip.
Rookies and professionals frequently miss this wear, put in new pieces, only to have that retainer slip past the circlip at a later date....destroying a whole bunch of pieces.
That retainer is cheap. When the clutches are worn this badly, replace it, too.
One little caution I'd add.
When the B3 clutches wear out, the B3 piston needs to travel so far, that the springs which return that piston go into coil bind. Once this happens that spring retainer gets a tremendous amount of pressure exerted on it, which tries to "push" that retainer right over the circlip.
Rookies and professionals frequently miss this wear, put in new pieces, only to have that retainer slip past the circlip at a later date....destroying a whole bunch of pieces.
That retainer is cheap. When the clutches are worn this badly, replace it, too.
__________________
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
01-28-2015, 03:23 AM
#26
Rennlist Member
Thread Starter
Thank you for your kind words!
YES!!! Greg is absolutely right, when you dig into your automatic you must inspect all parts thoroughly. If something is not perfect, replace it. All parts cost me about € 220 or US$ 260 from my local MB dealer. IMHO completely acceptable after 236,000 km and 22 years of service.
Do not drive until engagement of reverse takes a loooong time! I would estimate up to about 3 seconds is acceptable. Once the friction material is getting thinner, wear will increase rapidly.
My reverse needed about 2 seconds for a long time and I was not concerned. But all of a sudden time to engage reverse increased significantly and got worse.
My wife likes to drive my car in the winter here in Spain too (to cold to drive her 911 Targa) and she did not stop although I asked her to... So I put it on my liftbars until I had time to start the job .
If you continue until you can select reverse, engage the parking brake and go back inside to make coffee...it is definetly to late. You will damage internal parts like the alignment pin of piston B3. The hydraulic pressure is enormous!
IMHO I would not buy any aftermarket kits, just because they are cheaper than OEM parts from MB. There are aftermarket kits available with questionable quality. You don´t want to open up the automatic again after a short while because some friction discs failed. Greg has more info about this I´m sure.
If the automatic and the differential housing were never touched, I would not stop at B3, B1 and K1. Separate the rear portion with the ring & pinion from the transmission and remove B2 and K2 too. Once you are at this point it is simply checking clearances and replacing parts.
My transmission shifts like new and has no leaks. I hope it will stay like this for many years to come. If B3 fails again, I will not stop at the front section again....
YES!!! Greg is absolutely right, when you dig into your automatic you must inspect all parts thoroughly. If something is not perfect, replace it. All parts cost me about € 220 or US$ 260 from my local MB dealer. IMHO completely acceptable after 236,000 km and 22 years of service.
Do not drive until engagement of reverse takes a loooong time! I would estimate up to about 3 seconds is acceptable. Once the friction material is getting thinner, wear will increase rapidly.
My reverse needed about 2 seconds for a long time and I was not concerned. But all of a sudden time to engage reverse increased significantly and got worse.
My wife likes to drive my car in the winter here in Spain too (to cold to drive her 911 Targa) and she did not stop although I asked her to... So I put it on my liftbars until I had time to start the job .If you continue until you can select reverse, engage the parking brake and go back inside to make coffee...it is definetly to late. You will damage internal parts like the alignment pin of piston B3. The hydraulic pressure is enormous!
IMHO I would not buy any aftermarket kits, just because they are cheaper than OEM parts from MB. There are aftermarket kits available with questionable quality. You don´t want to open up the automatic again after a short while because some friction discs failed. Greg has more info about this I´m sure.
If the automatic and the differential housing were never touched, I would not stop at B3, B1 and K1. Separate the rear portion with the ring & pinion from the transmission and remove B2 and K2 too. Once you are at this point it is simply checking clearances and replacing parts.
My transmission shifts like new and has no leaks. I hope it will stay like this for many years to come. If B3 fails again, I will not stop at the front section again....