GM Auto all models

Marks 4WD Adaptors manufacture kits that allow the fitting of the GM TH350, TH400, TH700, and 4L60E automatic transmissions. They can be fitted with various engines such as Chevy V6 and V8, Holden V6 and V8, Oldsmobile V6 and V8, Buick V6 and V8.

Some vehicles being fitted with automatic transmissions and V8 engines will require the transfer case to be shifted rearward.

For information relating to engine installation parts refer to the relevant engine conversion sections.

To comply with Australian emission laws the new engine must have been manufactured the same year or later than the vehicle. The engine must also have all of the emission components connected, including the catalytic converter. The engine must also be run on unleaded fuel or LPG.

In Australia an engineer's report is required after the conversion has been completed. Contact your local RTA office for a list of engineers.

The automatic transmission output shaft for all kits is sold on an exchange basis (Australia only) and if not supplied with the original order a deposit of $110 will be charged. Change over shafts with a short spline on the front, or shafts that are pitted, rusted or heat damaged will not be accepted. The deposit will be refunded when a suitable shaft is received at our factory. Postage or freight is the responsibility of the sender. NOTE: Some TH700 and 4L60E kits do not require a change over main output shaft.

The GM Turbo Hydramatic 350 is a 3-speed automatic transmission. It can handle a lot of power and it is a relatively compact transmission. The standard GM Turbo 350 will bolt straight up to all Chevy V6 and V8 engines, Turbo pattern Holden V8 engines and Oldsmobile V6 and V8 engines. The Turbo 350 was also manufactured in different case variations that bolted directly to Buick, Oldsmobile and Pontiac V6 and V8 engines.
If you intend using a 253 Holden V8 or a Trimatic pattern 308 you will need to adapt the automatic transmission to the engine with another adaptor plate, which are generally available from any speed shop.
The TH350 has an overall case length of 546 mm/21.5". When coupled up to our 35 mm/1.4" adaptor housing gives you an overall transmission length of 581 mm/22.9".

Transmission and Transfer Case Mounting

The transmission has a mounting pad just behind the oil pan so that a cross member can be fabricated to support the transmission and transfer case.

Front Drive Shaft Clearance

The smaller drive shaft from an early model 40 series or a Hilux must be used with this kit. The adaptor is drilled to rotate the transfer case down on the right hand side to help with front drive shaft clearance however some modification will also be required to the oil pan to gain enough clearance. Marks 4WD Adaptors now stock a small shaft kit to help overcome this problem. For Small shaft kit info click here.

Transmission Mounting

The TH350 has a mounting pad on the rear of the main casing. When fitting this transmission a new crossmember with suitable rubbers will need to be fabricated to suit your vehicle.

The Turbo 350 has the following gear ratios: 1st 2.52:1, 2nd 1.52:1, 3rd 1.00:1

Engine Braking

As all automatic transmissions have limited engine braking on steep declines we would recommend you consider using our Rock Crawling Gears in the transfer case for improved performance and added safety when off road.

The Turbo Hydromantic 400 is basically the same design as the TH350 but a stronger version. The Turbo 400 is also a 3-speed automatic transmission. The standard GM TH400 will bolt directly to the Chevy V8 petrol, Chevy V8 diesel and Turbo pattern Holden 308 engines. Several case variations of this transmission were manufactured; they bolted directly to Jeep, Buick, Oldsmobile, and Pontiac V6 and V8 engines.

If you intend using a 253 Holden V8 or a Trimatic pattern 308 you would need to adapt the automatic transmission to the engine with another adaptor plate, which are generally available from any speed shop.

The TH400 has an overall case length of 616 mm/24.25". When coupled to our 35 mm/1.4" adaptor housing gives you an overall transmission length of 651 mm/25.625".

The Turbo 400 has the following gear ratios:

Car version: 1st 2.52:1, 2nd 1.52:1, 3rd 1.00:1

Truck version: 1st 2.50:1, 2nd 1.25:1, 3rd 1.00:1

Front Drive Shaft Clearance

Transfer Case Mounting

The TH400 has its rear mounting pad on the tail housing, this tail housing is removed to fit the new adaptor housing. For this reason you will need to fabricate a crossmember and or mountings to support the transmission-transfer case assembly.

Marks 4WD Adaptors manufacture a replacement oil pan (sump) with a mounting point that accepts an 08/1980 and later split transfer case gearbox mounting rubber. The oil pan is manufactured in cast alloy and has extra fluid capacity. The pan has been scalloped on the right hand side to accommodate the front drive shaft.

This special oil pan has also been designed to strengthen the rear of the transmission with bolts that fit through the transfer case adaptor housing and into the new oil pan.

The new oil pan comes with all the necessary bolts, screws etc. The original gasket is not used with the new pan, silastic is recommended.

This photo shows a MFK090 fitted to a transfer case along side a MFK315 oil pan.

Engine Braking

The 700R-4 is a GM 4-speed overdrive automatic transmission. The first of the 700R-4 appeared around 1982 in the US. Unfortunately the transmission developed a bad reputation, as early models were prone to failures. GM redesigned the 700R-4 in 1985 when a larger sprag was introduced in 1987.

If you plan to obtain an automatic transmission from any imported engine it is advisable you use the later post 1987 version. All of the 700R- automatic transmissions that were fitted to the Holden Commodore VN 1988 on are of the later model design.

The 700R-4 is available in two different case variations. The standard GM V8 version will bolt directly to Chevy V8 petrol, Chevy V8 diesel and Turbo pattern Holden 304, 308 and 350 C.I. engines.

The V6 Commodore was also fitted with the 700R-4 transmission. The V6 version has a different bolt pattern than the V8 version and therefore, will only bolt to a Commodore V6 engine.

If you intend using a 253 Holden V8 or a Trimatic pattern 308 you will need to adapt the automatic transmission to the engine with another adaptor plate, which are generally available from any speed shop.

The 700R-4 is an excellent choice of transmission in a 4WD vehicle as it features a low 1st gear, lower than any other GM auto, with an overdrive top gear, which is ideal for highway cruising.

Transfer Case Mounting

Our adaptor housing has been designed to extend the front drive shaft away from the oil pan for sufficient clearance, thereby eliminating any oil pan modifications. To support the transmission and transfer case the adaptor housing also has a mounting pad that accepts an 08/1980 and later split transfer case gearbox mounting rubber and cross member.

The 700R-4 and 4L60E both have an overall case length of 594 mm/23.4" and when coupled up to the 170 mm/6.7" adaptor housing gives you an overall transmission length of 764 mm/30.1".

The 700R-4 and 4L60E have the following gear ratios: 1st 3.06:1, 2nd 1.62:1, 3rd 1.00:1, 4th 0.70:1

The 4L60E transmission is electronically controlled and for correct operation requires a computer to control the shift points. The computer or PCM also manages the engine fuel and timing system. We recommend you use the engine that was factory fitted to this transmission.

The adaptor housing for the 4L60E transmission has been specially machined to accept the GM 24-mm diameter speed sensor. The speed sensor is required as it sends pulses to the PCM that are proportional to the vehicle speed. This information is translated by the PCM to provide smooth shift points under varying load conditions.

The early TH700 and 4L60E transmissions have a rear extension housing secured with 4-bolts. The latest model 4L60E transmissions are fitted with a 6-bolt rear extension housing. Marks 4WD Adaptors now manufacture kits to fit this transmission to all model Landcruisers. The kit part numbers for these kits all end with /6.

Front Drive Shaft Clearance

Front drive shafts fitted with a cardan joint must be rotated 180 degrees. The joint normally on the transfer case end of 60 and 70 series models will interfere with the transmission if not rotated. Marks 4WD Adaptors now stock a small shaft kit to help overcome this problem if required . For Small shaft kit info click here.

Transfer Case Relocation

The transfer case in all 4-speed models will need to be relocated rearwards. Transfer case relocation can be avoided with 5-speed models if a short shaft water pump is used along with a direct coupled fan.

Shifter Mounting and Display Kit to suit TH700 and 4L60E Transmissions

Marks 4WD Adaptors manufacture a Commodore, shifter mounting and display kit to fit all vehicles.

The universal kit consists of a TPS and mounting bracket, digital display and mounting bracket, bolts, screws etc.

The shifter is fitted to the transmission tunnel in the original gear lever position; this enables the original gearlever boot to be used, which makes the installation look very neat and professional. The shifter display can be fitted under the dash or near the shifter. The display indicates the gear positions, which are illuminated green while the actual gear selected is indicated with a red LED next to the relevant gear.

The display is also fitted with a fault indicator light, which is used to show any ECM or PCM problems. This light is also used to read the fault codes making it very easy to diagnose any problems.

The display is also fitted with a Lockup indicator light which is used to show when the torque converter is locked.

Engine Braking

The 4L80E is a GM 4-speed overdrive automatic transmission.
The 4L80E transmission is similar in strength to the old TH400 3-speed with the addition of an overdrive 4^th gear. This transmission is electronically controlled.

The 4L80E has an overall case length of 661 mm/26".

The 4L80E has the following gear ratios: 1st 2.48:1, 2nd 1.48:1, 3rd 1.00:1, 4th 0.75:1, Rev 2.077:1

Our adaptor housing has been designed to extend the front drive shaft away from the oil pan for sufficient clearance, thereby eliminating any oil pan modifications. The adaptor housing also has a mounting pad that will allow you to use a Landcruiser 4 or 5-speed gearbox mounting rubber and cross member to support the rear of the transmission as found on all of the split transfer case models.

The 4L80E has an overall case length of 661mm/26" and when coupled up to the 95.5mm/3.75" adaptor housing gives you an overall transmission length of 756.5mm/29.75".

The 4L80E transmission is electronically controlled and for correct operation requires a computer to control the shift points. The computer or PCM also manages the engine fuel and timing system. We recommend you use the engine that was factory fitted to this transmission.

Engine Braking