Borg-Warner 35 transmission

The Borg-Warner 35 transmission (BW-35) is an automatic transmission produced by the BorgWarner company. This article also applies to variations—the M-36 and M-37. When this article refers to "M-3x" it refers to all models. When model number specific it will use the exact model number.

The "3" in the number refers to the specific series of transmission. The M-3x, 4x, 5x and 6x transmissions are all aluminum cased transmissions that are related to the M-35 (the first of the aluminum Borg-Warner automatics). In this case the rising series number is relative to transmission strength—a larger number will withstand more power than a smaller number. This isn't, however, a general rule with Borg-Warner automatics. The earlier M-8 and M-1x cast iron case transmissions are much stronger than the aluminum models, although the M-6x may handle as much power as the M-1x series. The second number refers to a specific variation. This usually indicates a higher torque load capability, but may refer to other variations that may not increase torque rating.

The M-3x has three forward and one reverse gears. The selector lever varies depending on years and car models the transmission is used in. All models follow a quadrant which has six stations. Early models have two drive positions marked with a "2" and a "1" (P-R-N-D2-D1-L; Park, Reverse, Neutral, D2, D1 and Lock). These models start off in Second gear when in the D2 position. This is useful for economy in relatively flat terrain and for starting on slippery surfaces (wet mud, snow, ice, etc.). When placed in the D1 position the transmission shifts through all three forward gears. In "Lock" the transmission can be locked to prevent upward gear changes and will provide maximum engine braking in 1st gear and moderate engine braking in 2nd gear. By selecting L from starionary, or before an upward gear change into 2nd gear, the transmission will become locked in 1st gear. By selecting L from D2 or D1 while in 2nd gear, the transmission will become locked in 2nd gear or from D2 or D1 when cruising below 55 m.p.h (88 k.p.h.) will effect an immediate downward change and lock in 2nd gear. In both these instances, the transmission will automatically change down into 1st gear when the car speed drops below 5 m.p.h. (8 k.p.h.). Should 1st gear be required earlier, reduce the car speed to below 30 m.p.h. (48 k.p.h.) and effect a "kick-down" gear change. Many people assume they have a two speed transmission because they expect the first Drive position (D2) to shift through all three gears as all automatic transmissions have done since 1968. Some vehicles had the same system without the D1 and D2, instead just having D, and only 5 stations on the quadrant.

Starting in 1965 the M-3x was made with the now common P-R-N-D-2-1 shift arrangement (Park, Reverse, Neutral, Drive, Second gear, First gear). AMC called this "Shift-Command" to differentiate it from the D2/D1 models, since either could be ordered in an AMC/Rambler automobile from 1965-1967.

The M-36 was introduced in 1965. It is essentially the same as the M-35 except that it has provisions for an external transmission oil cooler. The M-35 was air cooled by the torque converter with a fan on it. The M-35 case has provisions to be drilled for an external cooler, but no U.S. models used an external cooler and do not have the internal provisions to mount one. There may be European models that were equipped with external coolers. An external oil cooler made it suitable for heavier vehicles and/or towing heavier loads. AMC used the M-36 behind the 232 six in their Ambassador starting in 1965.

The M-37 is first mentioned in the 1967 AMC Technical Service Manual (TSM). It was used behind the 232 in larger vehicles. It has a higher torque rating than the M-35 and M-36. By 1967 the M-36 was relegated to the 199 six, the 232 received the stronger M-37 in all AMC vehicles.

European models may differ.

Description

When the transmission of the motionless vehicle is placed in Drive, the transmission allows the vehicle to move off in first gear, then will change to second and then to third gear based on increase in road speed. The BW-35 will downshift from third to second and from second to first, also based on load. The transmission is equipped to produce kickdown and will upshift after kickdown if accelerator pressure is released following a kickdown.

As is common in automatic transmissions of its generation, power brought to the transmission via the torque converter drives hydraulic fluid. As the gears move faster or slower, pressure of the fluid increases or decreases in the case. Mechanical switching of gears is triggered by the increase or decrease of pressure. There are no electronic sensors or switches as found in modern transmissions. There is a Throttle Valve in the control valve body that is connected to the throttle linkage via a cable. This regulates internal pressure by throttle position. A secondary function of this cable is to down-shift ("kick down") to a lower gear when the Throttle Valve is in the full stop position (throttle pedal is fully depressed) and road speed is below a set point regulated by a mechanical governor on the output shaft.

The Borg Warner 35 automatic transmission comprises a torque converter and a fully automatic 3-speed hydraulically controlled epicyclic gear box. The automatic transmission provides three forward and one reverse gear ratio.

The hydraulic control system consists of a valve arrangement and an engine driven pump. The automatic transmission contains a planetary gear set consisting of two sun gears, two sets of three planet pinions contained within a planetary carrier and ring gear. Various speed ratios are obtained by holding or clutching various combinations of elements of the planetary train. This is performed by two bands, two multi-disc clutches and a one-way clutch.

The Borg Warner 35 was designed for use with Type F Automatic Transmission Fluid (ATF), which is far less common today than the Mercon/Dexron type.

Users

Initially produced in the U.S. in the 1950s specifically for engines of less than 200 cubic inches engine displacement and less than 140 hp (100 kW) (American Motors Rambler and Studebaker mainly). Prior and contemporary automatic transmissions were very inefficient and would work best with larger, more powerful engines, and even when used in those applications, the engines would often have higher compression ratios and more power than the manual transmission versions. Prior automatic transmissions were used with the small sixes in the USA in the late 50s and early 60s, but the heavy internal components of the early automatics were detrimental to economy, the main reason a lighter automatic transmission was developed.

In addition, lower differential ratios differentials were usually used in other automatic transmission applications to improve gas mileage (again due to the inefficiency of the earlier automatics, especially when used with small engines). The BW 35 was a more efficient transmission and was quite successful in the USA with the smaller engined cars. This also made it a natural for European cars that usually had much smaller engines than American cars of that era. Production was transferred in 1960 to the Borg-Warner plant at Letchworth in Great Britain. The BW-35 was offered to European automobile producers where it was widely used.

AMC

Used behind the 195.6, 199 and 232 six cylinder

• Ambassador 1965-1969
• American 1963-1968
• Rambler 1969
• Rogue 1967-1969
• Classic 1963-1966
• Rebel 1967-1969
• Marlin 1965-1967
• Javelin 1968-1969

BMC

• Austin 3 Litre
• Austin 1800 (and derivatives 2200 etc.) --- transverse installation using a Morse Hy-Vo chain to transmit the drive.
• FX4 Taxi
• Morris Marina
• See MG (below)
• other models

Citroën

• Citroën DS
• Citroën SM

Datsun

• 1967 Datsun RL411 SSS (SuperSportSedan) and 1600 ('Bluebird'); (same engine as the SR311 'Fairlady' roadsters).
• Datsun PL510 - Optional on both sedans and wagons.

MG

• MGB Mk II
• MGB GT
• MGC
• MGC GT

Jaguar

• XJ6 Series 1,2 & 3. engine size 2.8 and 4.2

optional on MK2 and S type and was also used on the Jaguar Mk2-derived Daimler V8 2.5litre saloon and the later V8 250 saloon

Reliant

Used in the Scimitar GTE SE5 with the Essex V6

The Rootes group (United Kingdom) (later Chrysler UK)

• Hillman Minx, Super Minx, Hunter, Minx (Arrow range 1725cc only)
• Humber Hawk, Super Snipe, Imperial, Sceptre, Arrow range Sceptre
• Singer Gazelle, Vogue, Vogue (Arrow range), Gazelle (Arrow range 1725cc only)
• Sunbeam Alpine, Rapier, Rapier (Arrow range), Alpine(Arrow range), Vogue (Arrow range)
• Hillman Avenger & Plymouth Cricket 1250, 1300, 1500 & 1600

In the mid-1970s, Arrow & Avenger ranges switched to B-W Type 45 4-speed transmission

Rover(UK)

• P5 3litre
• P5B 3.5litre V8
• P6 2000 & 2200
• P6B 3500 V8

Saab (Sweden)

Between 1970 and 1993, BW-35/37 transmissions were used in the models 99 and 900.

Triumph

• 2000/2500/2.5 Saloons
• Stag

Volvo (Sweden)

Between 1964 and 1976, BW-35 transmissions were used in the models 120, 1800, 140, 160 and 240.

The gear ratios were as follows:

• 1st gear: 2.39:1
• 2nd gear: 1.45:1
• 3rd gear: 1:1
• Reverse: 2.09:1

Ford UK & Australia

• Escort Mk1
• Capri Mk1
• Cortina Mk1, Mk2 & early Mk3 (later Marks used Ford C3)
• Corsair V4

Escort and Cortina gear ratios are as follows:

• 1st gear: 2.393:1
• 2nd gear: 1.450:1
• 3rd gear: 1.000:1
• Reverse: 2.094:1

Ford (Australia)

Early Ford Falcons had the three-speed Ford-O-Matic, from 1951. The gear ratios from the Ford Falcon XD specifications (3.3 and 4.1 litre Six; Borg Warner 35-3) are as follows:

• 1st: 2.39:1
• 2nd: 1.45:1
• 3rd: 1.00:1
• Reverse: 2.09:1

The 3.3 and 4.1 litre Six, 4.9 litre V8 used the Ford C4-3. The gear ratios from the Ford Falcon XD specifications are as follows:

• 1st: 2.46:1
• 2nd: 1.46:1
• 3rd: 1.00:1
• Reverse: 2.20:1

The 5.8 litre V8 came equipped with the Ford FMX-3, which was an evolved three-speed Ford-O-Matic (designed by Borg Warner Corporation), past the "MX" and "FX" or Cruise-O-Matic transmissions in 1958 to become the FMX in 1968. The gear ratios from the Ford Falcon XD specifications are as follows:

• 1st: 2.40:1
• 2nd: 1.47:1
• 3rd: 1.00:1
• Reverse: 2.00:1

Chrysler (Australia)

In the early 1970s, the Borg-Warner 35 transmission was also used in the 6-cylinder Australian Chryslers, Valiants and Chargers. The specification-change from the Torqueflite automatic transmission to the Borg-Warner 35 transmission was due a requirement for more local content. The Borg-Warner 35 transmission was used behind both the slant 6 and Hemi 6 engines.