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Page created by unknown. Additional info by ReaperHR and T.

New additions started May 9th 2007:

Back to Gearboxes Transmissions and Differentials

Powerglide Gearbox. Click to enlargen. Photo by Darren



Nobody123's Shed. Contains How to Assemble a Powerglide.

The Powerglide is a 2 speed automatic gearbox using a hydraulic torque converter. It was used by General Motors from the 1950s to the 1970s. Holden used the powerglide to replace the Hydramatic and it was later superseded itself by the Turbo Hydramatic or Tri-matic after other manufacturers had already moved from 2 speed automatics to 3 speed automatics. Chevrolet continued to use powerglide gearboxes into the early 1970s on their Novas and Vegas and they are still used today in racing (drag and mud) due to the boxes strength. The powerglide boxes have a 6 cylinder and V8 version which are very similar with the 6 cylinder box using many of the exact components the V8 box used, making it a very solid and reliable box for a Holden 6.

308-T's Shed


Powerglides in Holdens
Model Years Engine Shifter Part # Reverse Low Drive
HD 1965 - 1966 6 Column 7420946 1.82 1.82 Direct
HR 1966 - 1968 6 Column 7420946 1.82 1.82 Direct
HK 1968 - 1969 6 Column 7420946 1.82 1.82 Direct
  6 Floor 7436786 1.82 1.82 Direct
  307 V8 - 3924789 1.76 1.76 Direct
HT 1969 - 1970 6 Column 7420946 1.82 1.82 Direct
  6 Floor 7436786 1.82 1.82 Direct
  307 V8 - 3924789 1.76 1.76 Direct
  253 & 308 V8 - 2805133 1.76 1.76 Direct
  350 V8 - 3968033 1.76 1.76 Direct
HG 1970 - 1971 6 Column 7420946 1.82 1.82 Direct
  6 Floor 7436786 1.82 1.82 Direct
  253 & 308 V8 Column 5258738 1.76 1.76 Direct
  253 & 308 V8 Floor 2805133 1.76 1.76 Direct  


If a major failure does occur the gearbox should be removed, disassembled and inspected, the converter may also need to be replaced. Otherwise the powerglide box does not need periodical transmission fluid changes although to keep the fluid in the best possible condition the use of a transmission cooler should be used.

The powerglide transmission uses a dipstick similar to the standard engine dipstick (but far longer) and it is a good habit to keep an eye on fluid level and colour, if the colour begins to darken or smells burnt then it should be dropped out of the box and new fluid used to refill.

Checking Fluid Level

Unlike the engine where the fluid level is checked at rest the powerglide transmission fluid level needs to be checked after the vehicle is warmed up. Generally you can do this after returning from a drive or if you want to check the fluid then run the car at idle until normal operating temperature is reached (say around 82 degrees celcius on your temperature gauge).
1. Warm up the engine.
2. Shift the selector through all the gears finally stopping again in park.
3. Remove and clean the dipstick with a rag.
3. Switch off the engine and insert the transmission dipstick.
4. Withdraw the dipstick and check the fluid level.
5. Add fluid through the dipstick tube and repeat steps as required until fluid reaches the full mark. DO NOT overfill.

Signs of Incorrect Fluid Level

The transmission should be kept at the full mark on the dipstick and checked periodically, if for some reason though fluid does escape from the box the following signs may be seen.
1. The vehicle won't move even though gears are selected.
2. Slipping around corners.
3. Slow changes between gears (a prolonged gap between the two gears).
4. Gearbox changing gears at incorrect times (too early, too late).
5. Gearbox overheating.
If the gearbox is slipping but fluid is already at or very close to the full mark it may just be the age of the gearbox components causing problems, running a little extra fluid can sometimes fix this issue.

Oil Cooler

Flushing the Oil Cooler

When a fault has occurred with the transmission as with any geared mechanical device it should be drained and cleaned of any metal fragments or other materials which may have been deposited into the fluid. In the case of the Powerglide box these particles may gather in the oil cooler. To remedy this the oil cooler and lines should be flushed to remove any fragments or debris before the gearbox is used again. To do this simply add a few litres of extra automatic transmission fluid to the box, disconnect the exiting oil cooling line at the opposite end from the box and allow the car to idle. Automatic transmission fluid should flow from the line, make sure to run the fluid until you have caught as many extra litres as you added, if the fluid is still contaminated then repeat. If the fluid doesn't flow then check for crushed lines, failing that the cooler unit may be the issue and if so the radiator will need to be replaced (if it a bottom radiator unit). Compressed air can be used to blow out the cooler and lines but should be done with care.

Replacing the Oil Cooler (Radiator Type)

If a fault is detected with the oil cooler itself you can try clearing it with a reverse flush of compressed air. Failing that the oil cooler cannot be replaced without replacing the whole radiator.

Testing the Transmission

When testing the transmission the engine should be at normal operating temperature, you may also need a tachometer connected to be able to accurately gauge engine revs where required.

Line Pressure

Testing line pressure should be done with the brake pedal applied and the gearbox in park, the test should also not be run for any more than a few minutes to avoid damaging the box. Apply a pressure gauge to the pressure port, a stock powerglide should have a line pressure of between 140 and 150 PSI. Racing powerglide boxes can have line pressure of 200 PSI and above.

Level Possible Cause
Too low (less than 140 PSI) Low pressure may be caused by sticking valves (pressure regulator, modifier pressure) or leakage from the control valve body, case or the pump.
Too high (greater than 150 PSI) Pressures above 200 PSI may indicate a racing box rather than a stock box. Otherwise it may be caused by a pressure regulator fault.  
Stall Speed

The stock 6 cylinder powerglide box will have a stall speed of approximately 1500 rpm, naturally if it is a race modified or stall kitted box this could be far different. A stall speed test should be done by a professional in a controlled environment and should be performed in the driven range i.e. Drive, Low and Reverse gears. To test the stall speed hold the throttle open in the gear for around 5 seconds, allow 3 or 4 times that period for the transmission to cool down afterward by placing it in Neutral and allowing the engine to idle.

Stall Speed Possible Cause
Too low (around 1100 to 1200 rpm) Confirm the engine is tuned correctly, otherwise this is an indication of convertor stator clutch problems.

Description Convertor Stator Clutch Remedy
Cruises ok but low acceleration Slipping Various, replace converter or increase pressure
Seems to pull back at cruise and acceleration very poor Possibly installed backwards Reinstall or replace with one known to work
Acceleration in Drive over 30mph and low top speed, transmission overheating Locked engaged Replace torque converter  
Too high (greater than 1500 rpm) If the stall speed is above 1500 rpm it may indicate that the convertor is not getting the required fluid or that it is slipping.
Description Problem
Excessive rpm in all driven gears Direct clutch or rear clutch slipping
Excessive rpm in Drive only One way clutch slipping  



Shift Points
Throttle Upshift M.P.H Downshift M.P.H
Closed 11.5 - 16 10 - 15
Detent touch 37 - 51 21 - 36
Full 46 - 58 43 - 55  



Powerglide Automatic Gearbox bolted to a 179 Engine. Photo by HR Ambo. Click to Enlargen.


Powerglide Automatic Gearbox bolted to a 179 Engine. Photo by HR Ambo. Click to Enlargen.



HR Powerglide. Photo by HQ_SS. Click to Enlargen.


HR  Powerglide. Photo by HQ_SS. Click to Enlargen.


1957 V8 Powerglide. Photo by Joe Gibson. Click to Enlargen.

V8 Powerglide Bellhousing. Photo by . Click to Enlargen.

V8 Powerglide Bellhousing. Photo by . Click to Enlargen.



Darren's Shed

HRAmbo's Shed

HQ_SS' Shed

Joe Gibson's Shed




Back to Gearboxes Transmissions and Differentials