1987caddy Posted April 21, 2014 Share Posted April 21, 2014 I guess I need to get larger tires. My 95 with 4.63 gears and 235/75/15 tires (28in tall) and I'm turning 3k at 65mph Link to comment Share on other sites More sharing options...
Precise1 Posted April 21, 2014 Share Posted April 21, 2014 235/75/15 are actually 29" diameter (theoretically). Yes, I'd definitely upgrade to 30 or 31" tires but don't feel alone, many people have talked about 3k rpm @ 65mph over the years. Too damn high, if you ask me... My auto on 33's cruises 60mph @ 1,961rpm. The RPM's stated for the four cylinder diesel motors are most likely correct. four cylinders will almost always rev higher than a six cyclinder at whatever matching speeds. four cylinders have to spin faster to "keep up" with a slower turning six. 65mph, 4.625 gears, 32" tires, factory transmission, you should be spinning 2,191rpm. Factory auto gearing 65mph, 4.375 gears, 32" tires, factory transmission, you should be spinning 2,072rpm. This is only if both your front and rear diffs were swapped though But if your tach is showing 200rpm off, it's hard to say, other than that your engine is spinning where it should be, even though it's indicated incorrectly. I'm not sure where you got your info, but those numbers are also extremely low. What is with swapping diffs to get 4.375 gears as well? Please clarify, because this looks like misinformation... B Link to comment Share on other sites More sharing options...
adamzan Posted April 21, 2014 Share Posted April 21, 2014 I know a guy here that had a 95 manual that he swapped the 4.6 gears from an auto into. With the stock 235 tires, it screamed well over 3k at 100kmh... Link to comment Share on other sites More sharing options...
silverton Posted April 22, 2014 Share Posted April 22, 2014 235/75/15 are actually 29" diameter (theoretically). Yes, I'd definitely upgrade to 30 or 31" tires but don't feel alone, many people have talked about 3k rpm @ 65mph over the years. Too damn high, if you ask me... I'm not sure where you got your info, but those numbers are also extremely low. What is with swapping diffs to get 4.375 gears as well? Please clarify, because this looks like misinformation... B I got all the data from the FSM. FD ratio, and OD ratio. 4.625(auto) FD ratio, and .694 OD ratio. I used an RPM calculator to get what RPM it should be at using speed, gear ratio, FD ratio, and tire height. I included an automatic transmission with manual final drive ratio (4.375) just for comparison as I think it was brought up that it could have had its diffs swapped? Or maybe I just made that up. And also why I bolded an explanation after each one, to avoid misinformation getting thrown around. Link to comment Share on other sites More sharing options...
Nissanland Posted April 22, 2014 Author Share Posted April 22, 2014 Craps.......I forgot to get the axle information today, very full day of honey dues LIST!!!! Hahaha yea I know, but happy wife is a great and happy life...now let's hope I don't have to go into traction LOL. Well I'm sure I'll get it done tomorrow...til then... Link to comment Share on other sites More sharing options...
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