I have a 1987 Dolphin and one of the airbags started leaking so that it had to be filled every day. I tried the fix-a-flat trick, but that just made the entire airbag disintegrate! So don't try that unless you have nothing to lose...
Anyway I started searching for replacements. My originals are the single convolution type marked Airsleeve 4Q86 or possibly 4086. I couldn't find any of the Firestone replacements listed in this thread anymore.
I was about to give up and order the Air Lift kit when I got lucky and talked to a Firestone engineer that referred me to 3-T's RV products in Lake Havasu City, AZ. 800-223-1779 / 928-453-3040. They have a Repair Kit that includes a replacement air spring, new bottom bracket, air valves and hoses for one or both sides. For both sides of my 1987 the part number was T-9E3 and was $218.50 + tax and shipping. The air bag looks close to an exact replacement for the existing one. It might even have worked with the old bottom bracket, but the new one was already attached and has an adjustable slide to keep it from shifting. Installation was straight forward since it fit right into the existing top holes and I did not have to modify anything. Just make sure you follow the instructions and don't over tighten the top bolt (I found out the hard way it strips easily.)
Happy Trails
Eg00r
