In fourth gear/overdrive how many rpm does your car run at when doing 60 mph?

Most accounts of running the 3.58 diff do not mention that the engine sounds
strained, so I want to figure out what speed the engine is running at.

Alternatively, what is the fourth gear ratio?

 

I have a 3.2 - does that have a 3.58 diff ratio?
My car does 2400 at 100 km/h, a little over 60 mph, so about 2300 at 60 I guess

 

Not familiar with the 3.2, but I think it likely has a 3.73 from those numbers.

(been very busy with a spreadsheet)

 

.73 for cars with the ZF

.75 for cars with the 4L80E


Cheers
DD

 

FWIW: MPH = (FDR X Tire OD X RPM) / 336
Well....most accurate would be to double the static loaded radius for Tire OD (in inches)
but solving for RPM:


RPM = (MPH X 336) / (FDR X Tire OD)


Final Drive Ratio is the product of all gear reductions between Engine and wheels...so 0.73 X 3.58 for the studied case.

 

Here is a spreadsheet I already prepared, you just need to change the numbers to suit your car (it's currently with the X350 gear ratios & tyre sizes)

https://dl.dropboxusercontent.com/u/...g%20Sheet.xlsx

 

Thanks, but I already have one ... and can't do .xlsx anyways ... just .xls

Would 2200 rpm at 60 mph be just a tad on the high side then?

That assumes a larger tire than normal on the X300 (255/45-18) which
runs at 769 revolutions per mile.

The overall drive ratio seems to be about the same once overdrive and
differential gear ratios are taken into account.

X300 with 3.58 = .728 x 3.58 = 2.60
X308 with 3.08 = .831 x 3.08 = 2.55

but

X308 with 3.58 = .831 x 3.58 = 2.97

So a X308 with those tires, and a 3.58 is going to run 2300 rpm or so at 60 mph,
versus 2000 rpm with the stock 3.08.

Not so bad I guess compared to a Supra which would be running 2400 rpm at 60 mph,
and it never seemed strained at my usual cruise speed.

At redline, that still puts the speed at 173 mph which is just theory for me anyways.

 

So, plums, what do you have up your sleeve?

 

Approx. 2050 rpm at 60 mph for me this morning on way to work. FYI, 2350 rpm at 70 mph.