Truck is slow on the high way (help with gear ratios)

[doorgunner]

What happened was....I replaced the 2.9 (that turned 2600 rpm at 60) in my '89 wiff a 350 that turned about 2600 rpm at 60 using the same rear end.

So wut I did was replace my worn 26" tall tires with 28" tall tires...dropping my rpm down to 2200 at 60.

With the added power from the V8....everything is cool (wiff the exception that the back tires are much easier to burn down now...even figuring in the power-band stuff)


waaaaaaaaaaaaaaaaaaaahahhahahahhahaaaaaaaaaaa

 

[feellnfroggy]

He is probably running comparable hp to a 3.0 and less torque than a 4.0.

I wouldn't really worry too much about the 7.5, I wouldn't pay to regear it though.

Really? its a 302 swap, i wouldnt call the hp torque numbers comparable. Your c6 is the primary issue. it has different gearing than the original trans that came with your original motor. basically you need to look up the trans gearing for that year and the corresponding rear gear ratio to figure out that years final drive ratio. Then swap your rear gears to match the factory gear associated with the C6. This should bring your rpms down a little. If your gearing is too low, then YES a taller tire will help bring your rpms down.


I have to agree with not wasting the money on the 7,5 though, get yourself an exploder 8.8 with disc brakes. do the conversion and gearing all at once. youll net (possibly) a 31 spline axle system, and disc brakes all in one mod. To throw a number out there that you can give a try if you dont wanna look all that up, try 3.55 or 3.73

 

[85_Ranger4x4]

Really? its a 302 swap, i wouldnt call the hp torque numbers comparable.

Early '80's are nothing too hot...

Mustang GT is 175hp and 270 lb-ft... not exactly groundbreaking considering what Ford ran through that same axleshaft with a SOHC 4.0 putting out 210/254. Without the 4bbl and perkier cam a truck engine pumped out 133hp and 233 lb-ft.

With wear/age and potential modifications it is hard to tell what it is putting out now... I have been beating on my 7.5 with a 150hp 270lb-ft 5.0 for just about a year now and the only wimpers have been from the tires.