WHY mid-year PN change (M28/21-22 cam collar sleeve)
04-26-2017, 01:09 AM
#1
Rainman
Rennlist Member
Rennlist Member
Thread Starter
WHY mid-year PN change (M28/21-22 cam collar sleeve)
Hi all,
I have to replace the little metal collar sleeve on my 944 camshaft because the cam seal wore the old one out.
In doing so I found that there were 2 sizes of this part as well as 2 different seals, corresponding to each respective collar diameter.
I ordered 928 105 139 02 which is 30mm OD. I got a 30x47mm seal to go with it.
It appears that at some point in 1985-1986 both the 944 and SOHC 928 changed to this PN: 928 105 139 04. This is 32mm OD and there is a 32x47mm seal.
Looking at the PET for 944 and 928 it gives engine numbers for the changeover but since all the other parts around the sleeve/seal are identical, these "parts pairs" must be fully interchangeable.
944 engine series M44/07 and M44/08 vs 928 engines M28/21 and M28/22.
...now the question must be asked...WHY would they do such a change? Changing sizes means more parts they have to keep in service inventory rather than having a literal "one size fits all" for 944/928 cams and 944 Balance-shafts.
Any ideas?
I have to replace the little metal collar sleeve on my 944 camshaft because the cam seal wore the old one out.
In doing so I found that there were 2 sizes of this part as well as 2 different seals, corresponding to each respective collar diameter.
I ordered 928 105 139 02 which is 30mm OD. I got a 30x47mm seal to go with it.
It appears that at some point in 1985-1986 both the 944 and SOHC 928 changed to this PN: 928 105 139 04. This is 32mm OD and there is a 32x47mm seal.
Looking at the PET for 944 and 928 it gives engine numbers for the changeover but since all the other parts around the sleeve/seal are identical, these "parts pairs" must be fully interchangeable.
944 engine series M44/07 and M44/08 vs 928 engines M28/21 and M28/22.
...now the question must be asked...WHY would they do such a change? Changing sizes means more parts they have to keep in service inventory rather than having a literal "one size fits all" for 944/928 cams and 944 Balance-shafts.
Any ideas?
04-27-2017, 04:13 AM
#2
Rennlist Member
Perhaps the economics of seal availability? They had to buy a lot of these, if they switched to a more common seal size with more applications, it may have saved costs. Seems like a small thing but there's evidence of cost cutting throughout the years of development of these cars...18 years, thousands of cars, hundreds of thousands of parts...it adds up.