Transmissions (vehicle gearboxes)

01

Match input torque, gears, ratios and shift type

ZF's TraXon data sheet describes an automatic transmission system for heavy-duty special vehicles: the 12 TX 2610 SO accepts a maximum input torque of 2,600 Nm and the 12 TX 3420 SO 3,400 Nm, both with 12 forward gears from 12.92 in first to 0.77 in twelfth and four reverse ratios from 12.03 to 2.04. The TraXon DynamicPerform versions add a multidisk clutch starting module for mobile cranes with up to 5 axles and 3,000 Nm engine torque, and the TraXon Torque version adds an upstream torque converter clutch with a torque increase of 1.59. [1]

Allison's 4000/4200 Series specification sheet (edition 2009/06) lists a transmission with a one-stage, three-element polyphase torque converter, a lock-up clutch and six forward ranges. Gross input torque ratings depend on vocation: 2,400 N·m for general use, 2,508 N·m for fire and heavy-equipment-transport vehicles, 2,102 N·m for refuse and rigid rear dump trucks (the latter at up to 57,000 kg GVW), 2,203 N·m for the 4000 ORS articulated dump truck and 2,644 N·m for specialty and motorhome models. Mechanical ratios are 3.51, 1.91, 1.43, 1.00, 0.74 and 0.64 forward and 4.80 reverse, excluding converter multiplication; converter stall torque ratios run from 1.58 to 2.42 by converter model. Shifts are made by electronic controls with closed-loop adaptive shifts. [2]

At the light end, Fast Gear's C5J40T-B light-duty transmission lists 400 Nm input torque and 4,000 rpm maximum speed, with dual-lever operation and Eaton synchronizer technology. [3]

Inside an automatic transmission, gear ratios are set by engaging subsets of clutches and brakes around planetary gear sets. A Ford patent describes the clutch pack used for these shift elements: friction plates carrying friction material are interleaved with separator plates, each set splined to one of the two parts being coupled; hydraulic pressure drives a piston against the pack, a reaction plate at the far end holds it, and a return spring pushes the piston back to release it. [6]

Editorial calculation: the TraXon ratio spread is 12.92 ÷ 0.77 ≈ 16.8, while the Allison mechanical spread is 3.51 ÷ 0.64 ≈ 5.5 before torque-converter multiplication — compare spreads on the same basis. [1] [2]

Give the supplier the engine model, gross torque and power curve and governed speed, vehicle type and gross combination weight, duty (on-road, construction, mining, refuse, crane), the shift type wanted (manual, automated, torque-converter automatic), required starting and top ratios, retarder need, PTO requirements, mounting (SAE housing size), climate and quantity.

02

Check PTO provision, weight and oil fill

Allison lists a dry weight of 377 kg for the basic 4000 Series model, 405 kg with PTO drive provision, 411 kg with retarder and 439 kg with both, and an oil capacity including the PTO of 45 litres with deep sump or 38 litres with shallow sump. Its engine-driven helical PTO drive gear has mounting pads at the 1 o'clock and 8 o'clock positions, turns at 1.00 × engine speed, and is rated 930 N·m continuous for one PTO or 1,595 N·m in total for two. Mounting to the engine is SAE No. 1. [2]

ZF lists the TraXon at about 254 kg (2,600 Nm) or 268 kg (3,400 Nm) without auxiliaries and about 12.5 or 13.5 litres of initial oil fill without heat exchanger, rising to about 333–359 kg and 22.5–23.5 litres with the integrated Intarder, which provides up to 4,000 Nm or 600 kW braking. A clutch-dependent PTO is optional; the separate PowerDivide engine-dependent PTO fits between engine and transmission at the SAE interface and delivers 251 or 314 kW and 1,600 or 2,000 Nm, at about 168 kg. [1]

Fast Gear lists its C5J40T-B at 545.0 mm long, 60 kg in aluminium and 3.2 litres of oil with a ±4% deviation. [3]

Editorial calculation: PTO drive provision adds 405 − 377 = 28 kg to the Allison basic model, and the Intarder adds about 333 − 254 = 79 kg and 22.5 − 12.5 = 10 litres to the 2,600 Nm TraXon. [2] [1]

03

Add a transfer case for all-wheel drive

A transfer case takes the transmission output and divides it between front and rear axles, with a road ratio and an off-road ratio. ZF's transfer-case data sheet lists the VG 750/270 at 11,000 Nm maximum input torque, 3,500 rpm, ratio 1.00 on-road and 2.00 or 2.39 off-road, and 115/125 kg without/with differential; the VG 750/400 at 12,500 Nm, ratios 1.09 and 2.10 or 2.52, and 155/165 kg; and the VG 2700/400 at 35,000 Nm, 2,800 rpm, ratios 0.91 and 1.41, and 435/465 kg. Options include front-axle engagement instead of a longitudinal differential, a torque-split differential of FA : RA = 1 : 2.000, pneumatically activated differential locks under the ADM 3 control module, and a PTO NA200 rated 2,000 Nm on the VG 750/270. [4]

Fabco's TC-1702 service manual describes a two-speed, two-shaft, constant-mesh transfer case for rear-engine all-wheel-drive vehicles, rated 20,000 lb-ft input torque, 500 HP and 3,000 RPM, with direct ratio 1.00:1 or 0.85:1 and underdrive 2.52:1. Its shift mechanism is integral air cylinders: shifting between ranges and engaging the front-drive clutch are done by air-operated cylinders, and the vehicle must be stationary before shifting between high and low ranges or front drive. The manual's inspection steps cover the shift forks and the slots in the sliding clutches. It uses splash lubrication with SAE 50 heavy-duty engine oil, 12 US quarts, weighs 475 lb dry and has an aluminium housing. [5]

Editorial calculation: 20,000 lb-ft × 1.356 ≈ 27,100 N·m, 475 lb × 0.4536 ≈ 215 kg and 12 US quarts × 0.946 ≈ 11.4 litres. In first gear the 2,600 Nm TraXon multiplies input torque to about 2,600 × 12.92 ≈ 33,600 Nm at its output before losses, which is why transfer cases are rated far above transmission input torque. [5] [1]

For a transfer case, state the transmission model and its first-gear output torque, axle configuration, required road and off-road ratios, torque split or front-axle engagement, how and when range and front drive are shifted (air, electric; stationary or on the move), differential locks, PTO and emergency steering pump needs, and shaft centre distance.

04

What a transmission maker's offer should include

When requesting quotations, ask each supplier for the rating table by vocation, ratio sets, shift system, PTO provisions, dry weight and oil fill, installation drawings and the approved-lubricant list.

05

Where torque passes from starting device to transfer case

06

TraXon, Allison 4000 and Fast Gear values side by side

Rows cite the ZF TraXon, Allison 4000 and Fast Gear C5J40T-B sheets, plus the Fabco TC-1702 manual for the transfer-case shaft; efficiency, operating temperature, oil pressure and noise are not published in any of them.

07

Send the engine, vehicle and duty data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Engine: [model; gross torque N·m; power; governed rpm]
Vehicle: [type; GVW/GCW; axles; all-wheel drive?]
Transmission: [manual; automated; torque-converter automatic; gears; ratios]
Options: [PTO positions and torque; retarder; oil cooler]
Transfer case: [road and off-road ratios; torque split; shift method]
Installation: [SAE housing; length; weight limit]
Quantity: [units]

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