High Stall Torque converter question
Ashton Crusher
was asking if I would want to go with a high(er) stall converter.
Apparently the standard is around 1600 and he's saying it would have
more off the line power with a 2500 rpm converter. There must be a
downside or they would have built the car that way when they made it.
Anyone have any insight into the pros and cons of higher stall
converters? With the rear end that's in it, 2.78, I don't think the
engine will run much over 2000 even in high gear unless I'm going
pretty fast. Would that make it pretty inefficient?
Nate Nagel
yup, you always want the stall speed to be lower than cruise RPM.
nate
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Steve W.
If your racing it then get the higher stall. If you intend to drive it
on the street stay with the stock unit.
Think of it this way the stock unit is like letting out the clutch on a
manual trans at 1500rpms. The high stall is like waiting until 2500 rpm.
With a 2.78?? rear gear the high stall would be a cruising nightmare...
You would be cruising in 2nd gear just to keep the car moving!
--
Steve W.
Pete C.
"Steve W." wrote:
>
> Ashton Crusher wrote:
> > I'm have the transmission (TH400) redone in a 69 firebird. The shop
> > was asking if I would want to go with a high(er) stall converter.
> > Apparently the standard is around 1600 and he's saying it would have
> > more off the line power with a 2500 rpm converter. There must be a
> > downside or they would have built the car that way when they made it.
> > Anyone have any insight into the pros and cons of higher stall
> > converters? With the rear end that's in it, 2.78, I don't think the
> > engine will run much over 2000 even in high gear unless I'm going
> > pretty fast. Would that make it pretty inefficient?
>
> If your racing it then get the higher stall. If you intend to drive it
> on the street stay with the stock unit.
> Think of it this way the stock unit is like letting out the clutch on a
> manual trans at 1500rpms. The high stall is like waiting until 2500 rpm.
Not a good comparison.
When you let out the clutch in a manual vehicle, you start to apply
power to the drive train through the clutches slip range until the
clutch is fully applied and at it's minimum slippage (slight creep).
With a torque converter in an automatic, as soon as the transmission
engages the clutch bands on the 1st gear, the torque converter begins
applying power to the drive train through it's torque multiplying range
starting from idle RPM. The stall speed is the point at which the torque
converter is no longer providing torque multiplication and normally the
point that a lockup torque converter will be locked, somewhat similar to
a fully applied manual clutch.
>
> With a 2.78?? rear gear the high stall would be a cruising nightmare...
> You would be cruising in 2nd gear just to keep the car moving!
Ideally you would want the stall RPM to be slightly below the normal
cruising RPM.
Ashton Crusher
wrote:
There was a 2.56 option also available. Thank god it doesn't have
that.
Steve
You should definitely change the rear end gear before raising the stall.
high stall convertors generate more heat and hurt gas mileage,
especially if you wind up cruising below the stall speed so that its
always in "stall" mode.