On Tue, 16 Sep 1997 15:27:25 -0700 Christopher.Albers(at)bubbs.biola.edu
(Christopher Albers) writes:
> It seems as if Dick may have answered the question, but there does
>seem to be many different opinions out there so I'll ask anyway.
> When I built my rear end I had the option of using either the 3.89
>or
>the 4.22. I have the OD and Smitty recommended that I use the 4.22,
>as
>it came from the factory. So I did.
> Did I make a mistake here? From the driving impressions of those
>who
>have the 3.89/OD setup it seems as if I'm losing a bit of performance.
>
>Yet Dick says I'll ruin my car if I DON'T use the 4.22. Who is right?
>
>Or is there no right answer and this is just a matter of personal
>preference?
>
>Christopher Albers
Chris, I would say that you made a sound desision. Not only did you put
the Mfgr correct part, but you added some zip to boot.
You will be assured to know that you will be able to make it to 60 a full
second faster with the 4.22 than you could with the same setup on
the 3.89 gears.
Smitty gave you good advice here, and you should rest assured that
what you have will last a long time, and meet the needs of normal
driving.
There is a minor difference in attainable top speed, as you will not
quite
be able to get to 100 in non OD 4th, but do you really need that kind of
potential anyhow? If so, you probably wanted a miata.
Here is some OD techo stuff for gearheads.
With the std trans and a 3.89 rear diff, 60 MPH is at 3400 RPM in 4th.
With the OD trans and a 4.22 rear diff, 60 MPH is at 2950 RPM OD 4th.
With the OD trans and a 3.89 rear diff, 60 MPH is at 2720 RPM OD 4th.
Since the Alpine engine likes to hum along at 3200 RPM, the OD 3.89
setup will like to be engaged at 71 MPH.
Since the Alpine engine likes to hum along at 3200 RPM, the OD 4.22
setup will like to be engaged at 65 MPH.
This says that you need to consider the OD as sort of a high speed
cruising gear, and never let the RPMs fall below 2900 id OD.
BTW, third overdive is a total waste of gear, because it is so close
numerically to 4th std, but also wastes the 5BHP in doing so.
you could have just shifted into 4th, and gotten better performance
and fuel economy.
Jarrid Gross
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