gear ratio problem

[fat-lip-resto]

got a dana with 3.56 and a four speed 26" tall tires and i am at 4200 rpms at 70 mph what the %#^* is wrong

 

[rumblefish360]

Well, the small tire is a problem with that.
Clutch slipping? Old clutch, preesure on the plate from a miss adjusted fork?

 

[Mad Dart]

Is it not shifting into 4th gear? Shifter moves but it stays in 3rd?

 

[fat-lip-resto]

the clutch is new he doesnt think its slipping and he is sure it is shifting i am at a loss the car is not here and i am trying to diagnoss over the phone and do not know what else to tell him

 

[lhearold]

Are you sure its a 3:56? Did you get the ratio from a tag or did you actually count the revolutions to be sure?

 

[fat-lip-resto]

i will have him count next to make sure

 

[Dusterdude72]

sounds more like it has 4.11 ,4.30 or 4.56 gears in it or something.

 

[fat-lip-resto]

i worked it up on a ratio calculator and i think he put 4.56 instead of 3.56

 

[fishy68]

i worked it up on a ratio calculator and i think he put 4.56 instead of 3.56

My calculator says 4.56 gears with 26" tires will spin 4123 rpm at 70 mph so you might be right that he installed the wrong gears. 3.54 gears should only turn 3200 rpm at 70.

Only other thing that hasn't been mentioned is maybe the tach is 1000 rpm off?