I did some checking spent some money and time and mustang rear shocks will work. First I called WCCC and talked to Don. Don claims the shocks they sell fit and work just fine. No comment on actual KYB part numbers though. Next I emailed KYB tech support and here is a copy of my email and their reply.
Subject: Contact Technical Support 1967 Cougar shocks
I own a 1967 Mercury Cougar and want to replace shocks front and rear. As far as I can see KYB lists the same part numbers for rear shocks on 1967 Cougars and Mustangs, KYB PN KG5517. This is incorrect because cougars have longer rear leaf springs do to the longer wheel base necessitating shocks with longer travel. West Coast Classic Cougar sells KYB shocks they claim are the correct length though I question if they know what they are talking about.
http://www.cougarpartscatalog.com/kg-5517.html They do not list the KYB part numbers so I can't prove what they are selling. I would guess over the years the correct rear shock has been superseded to a mustang shock leaving the correct shock just a memory. I want a performance oriented shock and I'm not looking for a smooth ride. Most shocks these days have soft bump and stiff rebound. Nice for a smooth ride but not optimal for overall handling. What are your recommendations?
Thanks
Bill
"The KG5517 will work very well as long as the vehicle is still near the original factory ride height. To verify your suspension travel versus our shock you could do a quick static height measurement.
· With all tires on the ground, measure from the center-line of the upper mounting down to the center-line of the lower mounting. This measurement should be somewhere near the middle of our shock travel to allow sufficient compression and rebound movement.
· KG5517 extended length is 17.87” and compressed is 10.91”
"You should be very pleased with the handling characteristics of our Gas-a-Just monotube shocks for your Cougar.
Thank you for choosing KYB.
Tech support"
I did some thinking and I figure the rear suspension travel on compression is most likely no different than on a Mustang. Only the full extension of the suspension would be longer on a Cougar. So IMO adding length to Mustang shocks to make the extended length longer is a bad idea because it would make the compressed length longer increasing the chance of bottoming out the shocks before hitting the bump stops. Bad for the shocks and the weak upper shock mounts. The one inch of lost extended length will never be a problem as long as your not doing a remake of streets of San Francisco.
I ended up ordering all four KYB Gas Adjust shocks from Amazon. I wanted to give WCCC my business but $200 plus shipping was more than I wanted to spend. Besides not knowing if they would even work correctly. Last weekend I installed the shocks. Not a fun job without a drive on hoist BTW. The shocks coming off were a set of four Sears Allstate shocks that were installed in 1969. I would guess these shocks were correct for the car? Worked well for over 40 years anyway. The old front shocks were about 3/16" of an inch longer than the KYB's when fully extended. I did not check compressed length because the KYB's are high PSI gas and almost impossible to compress to check. The old rear shocks were about one inch longer than the KYB's fully extended. Compressed length not checked same as above. The only problem I ran into was in the rear and unrelated to shock length. The bushings were not compressed enough when the nuts were run down to the stop, aka no more threads. From experience the bushings should be compressed enough so they expand to approximately the size of the washer or close to it. This was not possible without modification. I ended up adding thee 5/16" flat washers to the top stud and two 5/16" flat washers to the bottom stud before screwing the nuts on to get the correct bushing compression.
Final results after a 20 minute road test, these shocks work great. Decreased body roll and quicker steering response and only a slight increase in harshness. The front to rear shock balance seems good also. Well worth the $146 shipped.
Other thoughts I should have measured ride height before and after because I swear it sits higher. Enough to notice anyway. I know it took everything I had to compress the shocks trying to check compressed length.
Bill
