Converter stall rpm?

[rpk250]

In the process of trouble shooting reasons why my hydroboost brake equipped GN will only hold about 4# of boost before the rear tires start spinning. Front brakes hold. This happens about 2750 RPM, and I supposedly have a 3500 rpm stall speed 10" lock-up converter. Is this a problem.

 

[Chuck Leeper]

What, if anything, have you done to the rear brakes??

 

[rpk250]

S-10 brake cylinders, soft brake shoes, new drums, bled multiple times. With the powermaster I couldn't even hold 1# of boost. So it's been an improvement with the hydroboost, but shouldn't my rear wheels hold until closer to that 3500rpm stall speed?

 

[Chuck Leeper]

Could be.... IF the converter is really a 3500 stall.
What does the stall rpm show @ 0 boost/0 vac?

 

[TurboTdr3.8]

3500 rpm converter does not mean it will dead stall that number , it is referring to flash stall before it is supposed to couple up , it depends on your engine torque and brake holding capability to name a few .

I used to run a 5500 stall in my big block Buick 455 it would only dead stall about 2200 but when you let go it would flash to 5500 to get the car moving it then was a bear dog then .

They is a sweet spot on all converters and you have to use that to establish what your combo likes . hopes this helps but maybe Dusty Bradford can give his insights on what happens also

 

[rpk250]

Well, I guess it's time to try a new converter. It's the only thing I haven't changed and I know I should be able to hold more then 4# of boost.

 

[Mr.Spool]

Y

This happens about 2750 RPM, and I supposedly have a 3500 rpm stall speed

Your not getting 3500,there is your problem.

 

[Dusty Bradford]

I spoke with him yesterday. He's seeing 1psi around 2400-2500 and is a good example of why stall speeds just don't mean a lot in the turbo world. He needs something looser down low to keep the tires from spinning but is already at 10% slip so just loosening will likely increase the slip. There may be some room to play with the converter by changing the stator and pump designs but I'd have to cut it open to see what it currently has.

This combo could benefit from the 9.5 NL in that you would gain an easy 400-600 of stall speed while also gaining 2-3% on efficiency.


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