928 Reliability Myths and Truths
12-21-2009, 06:44 PM
#16
Rennlist Member
Not really a low temp problem on the 84 box I drive. Have driven 40 miles to work when it was 9 deg F. I'd switch to a thinner fluid if it were an issue, though.
Synchros from 84 back would wear fast, and combined with aging clutch systems, wear-out. 85 and forward used a different design, considered much more durable.
Torque Tube bearings apply to all cars. Not really that hard or expensive to change them. Constantine developed a set of superduty bearings, too, that are a major improvement its reported. Removing tranny is not as hard as one would think.
Regarding thrust bearing failure, on the automatics the drive shaft is pinned in the back and the front. Its splined on both ends, but doesn't freely slide like on my chevy, its pinned with squeeze clamps front and back. Some confusion on root cause, either the driveshaft shortens when under twist, else the rear plate / torqueconvertor shifts rearword with torque application, but the bottom line is the driveshaft slips backward out of the front pinch point slightly, then stays out, causing the front flexplate to cave forward slightly. Can be several millimeters of shift. This results in constant forward pressure on the crankshaft, butting it up against the rear-pointing thrustbearing surface of the block main bearing. Oil doesn't film coat it, and it wears. Completely out. Then shortly thereafter, the big counterweight on the crank contacts the aluminum web inside the aluminum block. Its not happened to my cars, but from reading extensively here, this is for all practical purposes a terminal failure.
This is the type of failure that, again via reading here, has emerged with time. Some reports suggest it happened early in the car's history and might have been associated with improper set-up after driveline service. As the cars age more failure points might emerge, like the fuel line problems for instance.
Constantine and Porken each offer us new engineeered solutions, basically heavy duty clamps that don't let the driveshaft move inside the front spline. Key is to release the pressure first by loosening the original front clamp, checking with a simple dial gauge the degree of wear already present, levering the crank back, and applying a new heavy clamp or auxilliary additional clamp. Not so many people outside this list know about or believe or understand this problem. Its real and its bad. At some point, Porsche increased the recommended torque for tightening the front pinch bolt, and some guys, me included, have used the increased torque + loctite to stabilze the setup.
Torque convertor bearings and associated seals are replaceable. Again, having pulled a trans out and reinstalled it (three times last week due to some unusual circumstances unique to my car) I can tell you its not that bad to do this maintenance.
Synchros from 84 back would wear fast, and combined with aging clutch systems, wear-out. 85 and forward used a different design, considered much more durable.
Torque Tube bearings apply to all cars. Not really that hard or expensive to change them. Constantine developed a set of superduty bearings, too, that are a major improvement its reported. Removing tranny is not as hard as one would think.
Regarding thrust bearing failure, on the automatics the drive shaft is pinned in the back and the front. Its splined on both ends, but doesn't freely slide like on my chevy, its pinned with squeeze clamps front and back. Some confusion on root cause, either the driveshaft shortens when under twist, else the rear plate / torqueconvertor shifts rearword with torque application, but the bottom line is the driveshaft slips backward out of the front pinch point slightly, then stays out, causing the front flexplate to cave forward slightly. Can be several millimeters of shift. This results in constant forward pressure on the crankshaft, butting it up against the rear-pointing thrustbearing surface of the block main bearing. Oil doesn't film coat it, and it wears. Completely out. Then shortly thereafter, the big counterweight on the crank contacts the aluminum web inside the aluminum block. Its not happened to my cars, but from reading extensively here, this is for all practical purposes a terminal failure.
This is the type of failure that, again via reading here, has emerged with time. Some reports suggest it happened early in the car's history and might have been associated with improper set-up after driveline service. As the cars age more failure points might emerge, like the fuel line problems for instance.
Constantine and Porken each offer us new engineeered solutions, basically heavy duty clamps that don't let the driveshaft move inside the front spline. Key is to release the pressure first by loosening the original front clamp, checking with a simple dial gauge the degree of wear already present, levering the crank back, and applying a new heavy clamp or auxilliary additional clamp. Not so many people outside this list know about or believe or understand this problem. Its real and its bad. At some point, Porsche increased the recommended torque for tightening the front pinch bolt, and some guys, me included, have used the increased torque + loctite to stabilze the setup.
Torque convertor bearings and associated seals are replaceable. Again, having pulled a trans out and reinstalled it (three times last week due to some unusual circumstances unique to my car) I can tell you its not that bad to do this maintenance.
Last edited by Landseer; 12-22-2009 at 05:54 AM.
12-21-2009, 06:50 PM
#17
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I'm in the process of doing some research on my next vintage car purchase. I'm a kid of the 80's and have always loved the 928. I've had a hard time getting reliable information about the car by just asking generic Porsche people because the community is so 911 centric. I can also find 1000 books on 911's but almost none on 928s. As a result, I wanted to probe the 928 experts for some insights.
I'd be considering a manual transmission 928. I do all the work on my cars, including engine rebuilds, etc. This purchase would be my winter car. It would replace my 1989 XJS which has strange intermittent problems when the outside temp is below about 10F.
I'd be considering a manual transmission 928. I do all the work on my cars, including engine rebuilds, etc. This purchase would be my winter car. It would replace my 1989 XJS which has strange intermittent problems when the outside temp is below about 10F.
With the knowledge on this board and the fact I just bought 2 of these 928's I would ignore all the rumors and just zero in on what era you want then see what issues the people on her have found with that model. I have a 1982 and even with the quirks from LACK OF CARE by the PO the car is a great ride and very easy to sort out. If you get lost or have a question, just ask and you will get an hones answer from this group.
If you find one get a pro to look at it or maybe someone from this group can take a peek and see what they see. I had a friend look at my latest and it was worth the dinner it cost me for his time.
Good hunting.
12-21-2009, 07:02 PM
#18
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The 85> has Borg Warner design syncros which helps the shifting. My viewpoint on reliability is somewhat biased as I used to sell replacement parts for 928s.....and I sold Millions of dollars in parts ! I have seen receipts for repairs on a single car which EXCEED it's purchase price when new. Frankly some of the 928 owners bought a used 928 BECAUSE they could not AFFORD to buy a 911...simple as that .They then take it to a service shop ONCE that hurts so bad that they decide to "fix it " on their own even though the most they have ever done on a car is change wiper blades ! Beware those cars which jump from owner to owner too often with little or no service records. The 928 has very low ground clearance and is a poor deep snow car although the 86< S cars have a pretty good snow plow of a spoiler. Catch a pothole wrong and you rip off the A/C compressor which breaks the engine block. That said there are a lot of 928s with 150,000 plus miles on them, some 200,000 plus mile and heard of one around 400,000 miles on the original engine. So they must be somewhat reliable to get all those miles.
12-21-2009, 07:07 PM
#20
Rennlist Member
Lack of PO maintenance is a blessing. Especially if the lack is recent, the car was treated respectfully for most of its existence.
PO is then facing one more onslaught of heavy maint at the dealer:
$2500- $5000 for a TB job.
$2000 for major brake re-do
$2500 for motor mounts and assorted service.
He sells it cheap to me and I work like a dog for the equivalent of $1.50 per hour. 1000 hours + $2000 worth of parts later I'm driving it.
PO is then facing one more onslaught of heavy maint at the dealer:
$2500- $5000 for a TB job.
$2000 for major brake re-do
$2500 for motor mounts and assorted service.
He sells it cheap to me and I work like a dog for the equivalent of $1.50 per hour. 1000 hours + $2000 worth of parts later I'm driving it.
Last edited by Landseer; 12-22-2009 at 05:41 AM. Reason: spelling
12-22-2009, 12:25 AM
#21
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Unfortunately, "Porsche specialist" almost invariably translates into "911 specialist". A 911 specialists usually doesn't know anything about the 928, doesn't want to know anything, and will make you pay dearly if you make him learn on your car.
If you can't or won't do your own repairs and maintenance, you probably can't afford to run a 928. If you can do the work, it is a great car, and can be very reliable. The electrical system is pretty complex for cars of that era, but less so than new computerized vehicles.
This Forum represents an unbelievable information resource. Ten years ago, I couldn't find anyone who knew how the timing belt warning system worked - today, we have an aftermarket tensioner system developed by one of the members here!
If you get a 928, buy the 928 info CD set from Jim Morehouse (search is your friend), read a lot and ask for help when you need it. We, and the other vendors, can supply any 928 part available from Porsche, plus many aftermarket and OEM parts and accessories.
Jump in - the water in the Shark Tank is great!
If you can't or won't do your own repairs and maintenance, you probably can't afford to run a 928. If you can do the work, it is a great car, and can be very reliable. The electrical system is pretty complex for cars of that era, but less so than new computerized vehicles.
This Forum represents an unbelievable information resource. Ten years ago, I couldn't find anyone who knew how the timing belt warning system worked - today, we have an aftermarket tensioner system developed by one of the members here!
If you get a 928, buy the 928 info CD set from Jim Morehouse (search is your friend), read a lot and ask for help when you need it. We, and the other vendors, can supply any 928 part available from Porsche, plus many aftermarket and OEM parts and accessories.
Jump in - the water in the Shark Tank is great!
12-22-2009, 12:38 AM
#22
Track Day
Thread Starter
12-22-2009, 03:09 AM
#23
Nordschleife Master
As much as I love the 928, I don't know if it would make my top 100 choices for a winter daily driver.
12-22-2009, 03:30 AM
#24
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Having that extra 'wiper speed is cool:
1. It's raining slightly
2. It's raining heavily
3. I'm driving at 100+ mph, and OMG IT'S RAINING, HOW WILL I SEE?!?!?!?!?
Why you denizens of places where it snows in winter don't just MOVE, escapes me.
12-22-2009, 08:34 AM
#25
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We winter drive our '86.0, stick, LSD. It is an OK winter car. Your spring perch adjusters will sieze due to salt if driven enough. We drive it through reasonably heavy snow, but garage store it, so I'm not sure about the doors freezing - this is a problem on many cars around here as we get the 32F rain followed by 0f temps as fronts move through.
12-22-2009, 09:16 AM
#26
Race Car
I have rebuilt 4- 928's 82/85 Euro/86.5 and 86 a Super Charged and always come from the same angle, replace everything that is an maintenance item. You will get the it takes 10K to get a 5K car, I never found this unless you get a worn out wreck. If you do put 10K into a 5K car this means you went through it and now have a new car that will last until your tired of it, and it's not a Honda. Where can you get a 60K and above car with all its engineering at a low price look at the 928.
Your list is correct, you need to budget yourself for refreshing any older car. I have a lift so it makes things a lot easier but working on this car is not any harder then any other car. You have the advantage of a lot of good fanatics and a lot of parts and documentation available to you. Seems like you can do your own work so parts are what you need to concentrate on. If the paint is good and the interior is pretty good you have a plus on your side. now is a good time to purchase one due to the economy.
Remember a lot of electrical problems are a mystery to many and can be frustration but its a journey and fun once its all sorted out. I find these cars very reliable once gone over and a blast to drive, besides you never see another one on the road.
I do the following on every car:
All ignition parts
All timing belt related parts
Intake including vacuum and fuel lines
Shocks
Filters
Motor Mounts and oil pan gaskets
All the transmission issues I ran into on the Automatics are adjustments, fluid levels and lack of fluid changes.
The manuals are worn out shifter bushings causing sloppy shifting.
Flex plates are a big deal and need to be checked before you buy an automatic.
What I have found a 3-rd or 4th owner gets a car that has been neglected, down on power does not shift right and takes it to a Porsche dealer and gets a pricing shock. These cars degrade over time due to incorrect or lack of maintenance and the last owner dumps them cheap, my 928 cents worth Good Luck!
This gets you back to new then you work on the little stuff.
Your list is correct, you need to budget yourself for refreshing any older car. I have a lift so it makes things a lot easier but working on this car is not any harder then any other car. You have the advantage of a lot of good fanatics and a lot of parts and documentation available to you. Seems like you can do your own work so parts are what you need to concentrate on. If the paint is good and the interior is pretty good you have a plus on your side. now is a good time to purchase one due to the economy.
Remember a lot of electrical problems are a mystery to many and can be frustration but its a journey and fun once its all sorted out. I find these cars very reliable once gone over and a blast to drive, besides you never see another one on the road.
I do the following on every car:
All ignition parts
All timing belt related parts
Intake including vacuum and fuel lines
Shocks
Filters
Motor Mounts and oil pan gaskets
All the transmission issues I ran into on the Automatics are adjustments, fluid levels and lack of fluid changes.
The manuals are worn out shifter bushings causing sloppy shifting.
Flex plates are a big deal and need to be checked before you buy an automatic.
What I have found a 3-rd or 4th owner gets a car that has been neglected, down on power does not shift right and takes it to a Porsche dealer and gets a pricing shock. These cars degrade over time due to incorrect or lack of maintenance and the last owner dumps them cheap, my 928 cents worth Good Luck!
This gets you back to new then you work on the little stuff.
12-22-2009, 10:09 AM
#27
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The BEST 928 expert will be YOU since you will know the car inside out before you buy just by going over PPI inspection list.
This I can 100% guarantee you in your search
1. There are no 100 point cars for sale.
2. ALL cars are inflated as far as condition and probably price
3. SEEING all the different models of 928 will help you decide what you want as far as trim package and such.
4. The car only driven on Sunday by a little old lady has low miles, yes, 1/4 mile at a time in most cases.
I am now looking at buying #3 928 since I do stupid things like that when I find a car worth buying that is LOW in the market place.
Just keep asking questions, there are no DUMB questions just Dumb answers.
PS our heat works GREAT in the 928 But we are 20's at night and 50's during the day.
12-22-2009, 11:13 AM
#28
Rennlist Member
Be patient, there are a lot of really nice cars at all price points. Great time to look and buy.
I've somehow acquired two 32 valve cars with around 70,000 miles whose long-term owners had them sitting and were resigned to let them go to the next person that would appreciate them and get pleasure from them. Both needed the maintenance but they were incredible values. Rocket ships, both of them.
And we saw that beautiful 86.5 5 speed change hands to Firemed for sub $4,000. I liked that car. Maintenance was fairly current. I helped him inspect the timing belt before he hopped-in and drove to 1000 miles to florida.
Some memorable and recent beautiful cars that changed hands are the early green Kermit, Blue 82 with 3500 miles, the light blue 85 Dwayne found with 12,000 miles and the very nice medium blue early car that Ed has in Bozeman. Another was the Perlglantz white 87 S4 5 speed that popped up in Annapolis. Needed its midlife maintenance, too, but what a striking and unusual shark.
Poke around and read a bunch, you will find one!
I've somehow acquired two 32 valve cars with around 70,000 miles whose long-term owners had them sitting and were resigned to let them go to the next person that would appreciate them and get pleasure from them. Both needed the maintenance but they were incredible values. Rocket ships, both of them.
And we saw that beautiful 86.5 5 speed change hands to Firemed for sub $4,000. I liked that car. Maintenance was fairly current. I helped him inspect the timing belt before he hopped-in and drove to 1000 miles to florida.
Some memorable and recent beautiful cars that changed hands are the early green Kermit, Blue 82 with 3500 miles, the light blue 85 Dwayne found with 12,000 miles and the very nice medium blue early car that Ed has in Bozeman. Another was the Perlglantz white 87 S4 5 speed that popped up in Annapolis. Needed its midlife maintenance, too, but what a striking and unusual shark.
Poke around and read a bunch, you will find one!
Last edited by Landseer; 12-22-2009 at 02:13 PM.
12-22-2009, 12:32 PM
#29
Drifting
What kind of price range are you looking for? THat will help sort which years you are looking into. I've had three and all were well documented and were fantastic for the times I've had them. My current one I've had 5 years and I'm sure I'll regret selling when someone finallys comes around, but it has been nothing but good to me. even fantastic to drive moderately at Watkins Glen.
