cummins6900 Posted December 10, 2012 Share Posted December 10, 2012 Hello, My name is George and I collect older cf mack fire trucks. Right now I have 2. The one I need help with is my 1980 CF 600 75' scope. Top speed is only 45, 49 down a very steep hill. lol. Right now it is a real dog up hills as well. It has a Allison Auto, has the stock 20" mack wheels. What I need to know is if I wanted to swap out the stock reaend for a modern road gear with say 22.5 wheels, what gear ratio would I need to look for and from what type of truck will work? I am also looking for a jake for that same truck. It has the Gold motor, not sure of the hp or model # but i'm sure you all will. They tell me that they are hard to find, but out there. I would like to fix this truck up, it only has 30,000 miles and is still a pup, besides that it has appeared in several tv shows and several, several movies as well. The truck runs strong just not very fast in traffic/highway speeds. If anyone out there knows alot about the cf scopes please contact me back, i have a hyd. pump problem as well, I think i need a new one. Thanks, George Quote Link to comment Share on other sites More sharing options...
David Posted December 11, 2012 Share Posted December 11, 2012 First, we need pictures. Second, we need pictures. Third, 22.5" wheels will fit on 20" hubs. Forth, 10x20 and 11.00x22.5 are the same revolutions per mile. Fifth, find out what rear ratio you have. Sixth, we need pictures. Quote Link to comment Share on other sites More sharing options...
cummins6900 Posted December 12, 2012 Author Share Posted December 12, 2012 Hi, I will get some pics up soon. I know 22.5 wheels won't fit on 20" hubs. I am wanting to know if I can change out the whole rear end that already has 22.5's on it that will run at hi- way speeds, I'mgetting tired of people giving me the finger because I am holding up traffic making a funeral procession. OR what can I do to make this truck go faster? I will get the rear end ratio asap. Quote Link to comment Share on other sites More sharing options...
David Posted December 12, 2012 Share Posted December 12, 2012 22.5" wheels WILL fit on 20" hubs. Your ratio should be stamped on the rear. With a direct trans and 45 mph and 10x20 tires you are probably around 5.55. If that is the case, 4.17 will put you at about 60 mph. Your engine is probably a 237. Look on the front right corner of the engine for a 675 stamped into a flat spot in 1/2" high numbers. Quote Link to comment Share on other sites More sharing options...
fxfymn Posted December 12, 2012 Share Posted December 12, 2012 I would ask some of the other CF Aerialscope owners what they are using before I spent a lot of time and money doing something you might regret. The Aerialscopes are heavy and upping the rear end ratio will change the truck's ability to accelerate and climb hills. Not saying it won't work, but I would want to know before I did the work. A two speed rear end may prove to be more feasible.Remember, most fire apparatus was specified for acceleration ability, not top end speed. Quote Money, sex, and fire; everybody thinks everyone else is getting more than they are! Link to comment Share on other sites More sharing options...
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