We recently reached out to the guys in Summit Racing’s renowned tech department—the largest full-time staff in the industry—to identify and answer five common tech questions they hear on a consistent basis. With help from Summit Racing’s tech advisors and other industry experts, we’ll answer those questions here at OnAllCylinders. Today’s topic: transmissions.

The specific question: “What type of transmission do I have?”

It’s a basic question, but according to Summit Racing technical department supervisor Norm Koval, it’s a topic that comes up quite often among customers. It’s also a key question central to your vehicle’s performance, and it needs answered before you can proceed with a variety of performance or maintenance projects.

We have all the confidence in the world that you’ll be able to distinguish between a basic automatic or manual tranny. Now, with help from Koval and the Summit Racing tech staff, we’ll help you figure out which specific automatic or manual transmission plants your vehicle’s rear wheels.

We’ll start with common automatic transmissions.

Automatic Transmissions

Automatic TransmissionSome transmissions may have a code stamped into their case or a tag riveted to them. According to Koval, the easiest way to identify an automatic transmission, though, is by transmission pan shape. “Almost all have their own shape and pan bolt design,” Koval said. “Some are square; others are shaped like Louisiana or Texas or some other comparable shape.”

We compiled a slide show of specific pan shapes and matched them up to their automatic transmission counterparts. Find your pan shape—and ultimately your automatic transmission—in the images below:

gm powerglide transmission pan gasket
gm th350 transmission pan gasket
gm th400 transmission pan gasket
700r4 gm transmission pan gasket
ford c4 transmission pan gasket
ford c6 transmission pan gasket
ford aod transmission pan gasket
ford e4od transmission pan gasket
chrysler torqueflite 727 transmission pan gasket
chrysler 905 transmission pan gasket

GM Powerglide: 14 Pan Bolts

TH-250, TH-250C, TH-350, TH-350C, TH-375B: 13 Pan Bolts

GM TH-375C, TH-400, TH-475, 3L80, and 3L80HD: 13 Pan Bolts

GM TH-700-4R, 4L60, 4L60E: 16 Pan Bolts

Ford C-4 and C-5: 11 Pan Bolts

Ford C-6: 17 Pan Bolts

Ford AOD

Ford E4OD and 4R100: 20 Pan Bolts

Chrysler 727/A518: 14 Pan Bolts

Chrysler 905/A500: 14 Pan Bolts

Another way to determine your transmission is by measuring the overall dimensions. The good folks at Summit Racing also provided us with charts for that:

GM Automatic Transmissions
Type1st Gear2nd Gear3rd Gear4th GearOverall LengthBellhousing-to-Transmission Length
TH-3502.521.521.00--27-5/8" *20-3/8"
TH-4002.481.481.00--28-1/4" +26-3/4"
TH-700-R4 & 4L603.061.621.000.7023-3/8" # 22-3/8" #
*With 6″ (short) tailhousing+With short tailhousing#Except Corvette
Ford Automatic Transmissions
Type1st Gear2nd Gear3rd Gear4th GearOverall LengthBellhousing-to-
Transmission Length
C42.461.46 1.00--30-1/2"20-1/4"
C62.461.46 1.00--30-1/2"22 1/2"
AOD2.401.46 1.000.6730-3/4"22-1/4"
E40D2.711.53 1.000.7037-1/2"29-3/8"
Chrysler Automatic Transmissions
Type1st Gear2nd Gear3rd Gear4th GearOverall LengthBellhousing-to-
Transmission Length

Manual Transmissions

Manual TransmissionManual transmissions are a little bit trickier to identify, so we turned to our friends at Hurst, who have assembled a handy assortment of diagrams to help you positively ID your manual tranny. Click on your standard transmission speed below and match your manual tranny to the external characteristics and diagram notes:

Manual Transmission ID

“As you look things over you may notice casting bosses or provisions on your transmission’s tailshaft housing,” Koval said. “Take note of the number and location. Other things to consider: On the main case, where is the inspection cover…is it a side cover or a top cover? How many bolts secure the cover to the main case and is one edge of the cover curved or straight?”

The selector arms will also help you determine the ID of your transmission, according to Koval. “How do the selector arms mount? Are there mounting studs protruding from the side case or are the selector arms secured with a bolt instead?

Using these clues and the diagrams above, you can narrow down the identity of your manual transmission. Once you’ve made a positive ID, your sales rep or tech advisor can steer you in the right direction for transmission replacement components, performance upgrades, rebuild kits, and other items to help harness all your vehicle’s power.

Author: David Fuller

David Fuller is OnAllCylinders' managing editor. During his 20-year career in the auto industry, he has covered a variety of races, shows, and industry events and has authored articles for multiple magazines. He has also partnered with mainstream and trade publications on a wide range of editorial projects. In 2012, he helped establish OnAllCylinders, where he enjoys covering all facets of hot rodding and racing.