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GM Turbo 400 Deep Transmission Pan

Part Number 9683

PML TH400 Deep tranny pan, as-cast
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PML TH400 Deep tranny pan, powder coated
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PML TH400 Deep tranny pan, polished
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As-cast finish
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Black powder coating
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Polished finish
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Volume: 2 quarts over stock "car" type pan

Dimensions: Click here for dimensions. Fin height about 0.220 inches.

Number of Bolts: 13

The PML GM Turbo 400 deep transmission pan fits cars and trucks with the GM TH 400 transmission. This transmission is found in GMC and Chevy vehicles such as:

  • 1970-76 models of Corvette, Chevy, Cadillac, Olds, Buick
  • Blazer (2WD and 4WD)
  • Hummer H1, 1991 and 1992
  • Jaguar (this pan has been installed on a 1991 XJS)
  • Jeep
  • K1500, K2500, K3500 (2WD and 4WD)
  • Ferrari

The transmission was first available in 1964. This pan is the same depth and capacity as the stock TH400 "truck" pan.

If your stock pan has a dipstick receiver on the side of the pan, a PML Turbo 400 is not compatible with your vehicle.

The pan has a boss that can be machined for a temperature sensor.

The TH400 transmission is called Super Turbine 400 or Turbo 400 in the racing field and is formally called THM400 for Turbo-Hydra-matic 400. It first appeared in cars in 1964 and continued in production in the 1980s. In 1980s GM changed the name to 3L80.


  • Thick wall construction for strength
  • Gasket flange machined flat for a secure seal to the transmission housing
  • Finned for heat dissipation
  • Top quality sand cast aluminum
  • Drain and magnetic drain plug for easy servicing

Design Updates: In January 2008, PML moved the drain plug to bottom and temp sensor boss to driver's side. In 2017, we made the boss on the driver's side internal to the pan. These updates allow four wheel drive vehicles, such as Blazers, K1500, K2500, and K3500 to avoid drive shaft interference with the PML pan.

We have one of these pans on SPECIAL.

PML Th400 deep transmission pan package

Included with Transmission Pan

PML includes a new mounting hardware with each pan. The flange of the PML pan is much thicker than on the stock pan so the stock bolts would not be long enough.

A magnetic drain plug is also included with the hardware for each pan. The magnet on the end of the drain plug can capture small bits of metal in the fluid.

Inside of Pan, Optional Temperature Sending Unit Machining

Image shows the inside of the pan. Click on image to view larger.

There are three locations on this pan that can be machined for a temperature sending unit. The bosses (thick areas) on the inside of the pan are located on:

  • driver side
  • passenger side
  • rear of the pan near the drain hole

These areas can be drilled and tapped for 1/8 NPT to 1/2 NPT holes. The default is 1/8 NPT if you order through the web site. Please call to order if you require a different size. There is a $45.00 machining charge.


This PML pan is designed to work with the stock filter and stock deep pan tube, bolt and sleeve. The stock deep pan tube is GM part number 8629526.

The early valve body uses a side mount filter. This "old style" filter could hit the internal boss. One customer with the early valve body, ground off the boss. Another customer drilled a hole in the valve body to hold the "new style" filter in place on his old valve body. He had switched to the new style filter before getting a PML pan. He found the old style filter to be a "bad design" since it kept sucking air.

PML Transmission Pan Compared to Stock

PML Transmission Pan Part Numbers 9591_9683 height compared to stock  PML Transmission Pan Part Numbers 9683, compared to stock
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These images show this PML transmission pan compared to the stock pan.

PML Transmission Pan Features

  • Increased oil capacity for cooler temperatures
  • Sand-cast aluminum with raised fins
  • 3/16-inch thick wall construction to add strength to the transmission case
  • 3/8-inch thick gasket flange will not bend when bolts are tightened
  • Machined gasket surface for a secure seal
  • Boss cast into pan can be machined for a temperature sensor
  • Drain hole and magnetic drain plug for easier, less messy maintenance

All PML transmission pans ship with new mounting bolts and a magnetic drain plug.

If you would like PML to machine your pan for a temperature sending unit, there is an additional charge of $45 .

Find out why you should buy a PML transmission pan.

Learn more about finishes and construction of PML parts.

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