944 Final Drive — Ring & Pinion, Backlash, Oil & Torques

Factory setup data for the 944's final drive — the hypoid ring-and-pinion at the rear of the transaxle. Because the 944 is a transaxle car, this gear set sits with the gearbox at the back, sharing its housing and (on manual cars) its oil. The manual and automatic cars use different final drives: the five-speed manual runs the Type 016 J / 016 K unit, and the three-speed automatic the Type 087 N unit. Their setup values — backlash, bearing preload and the master-gauge dimensions — are not the same, so match the data to the transaxle you have.

For the gearbox side of each unit see the manual transmission data and the automatic transmission data. The ratios, gauge readings and shim thicknesses on this page are dimensionless numbers or fixed millimetre sizes; only the tightening torques switch between metric and imperial.

How the pinion and ring gear are matched

The pinion and ring gear are paired at the factory and run on special testing machines to find the axial pinion position that gives the quietest, smoothest mesh in both directions. That position is set by moving the pinion along its axis while keeping the ring-gear backlash inside tolerance. The two gears are a matched set and must always be replaced together — never mix a pinion from one set with a ring gear from another.

Each spare ring gear carries an etched deviation value "r", the offset from the production master gauge, given in 1/100 mm (for example, an etched "25" means r = 0.25 mm). During a rebuild you feed this "r" into the shim calculation so the replacement gears sit at the same quiet-running point the factory found. If a ring gear does not carry an "r" — which is the case for units built with the production distance Po instead — you must measure the installed pinion position with the universal gauge before removing it, and use that measured value as "r".

The adjustment is a shim game on four shims: S1 + S2 set the differential-bearing preload and the backlash on the ring-gear side, and S3 + S4 set the pinion-bearing preload and the pinion's axial position. Adjustment is only needed when a part that directly affects the mesh is replaced — the transmission case, the final-drive cover, the gear-carrier housing, either set of tapered-roller bearings, or the ring-and-pinion itself.

Manual final drive — Type 016 J / 016 K

Backlash and bearing preload

These are the target figures the shim selection has to hit on the manual unit. Bearing preload is expressed as a rolling (friction) torque read with a torque meter, in newton-centimetres.

Item	Specification
Ratio	9 : 35 (code "K 935", Klingelnberg teeth)
Hypoid displacement (Vo)	12 mm
Ring-gear backlash	0.10 mm to 0.20 mm
Pinion-bearing preload — new bearings	200 Ncm to 400 Ncm rolling torque
Pinion-bearing preload — used bearings	30 Ncm to 60 Ncm rolling torque
Differential-bearing preload — new bearings	at least 250 Ncm rolling torque

Individual backlash readings, taken at four points 90° apart around the ring gear, must not differ from each other by more than 0.05 mm — a bigger spread means the ring gear or the matched set is not seated correctly and must be re-checked. The rolling-torque figures apply to new tapered-roller bearings; the friction torque of used bearings need not be re-measured on the differential side, and drops to the 30–60 Ncm band on the pinion.

The setting dimensions and shim maths

The pinion's axial position is found from the master-gauge length Ro and the etched deviation r. The shim behind the pinion head is S3 = e + r, where "e" is the dial reading against the master gauge. The manual unit changed its master-gauge length across the model run:

Setting dimension	Value
Master gauge Ro — 016 J/K up to model '88	59.65 mm
Master gauge Ro — 016 J from model '89	58.15 mm
Pinion preload allowance (Stot constant)	0.30 mm
Differential preload allowance (Stot constant)	0.50 mm
Ring-gear lift (constant, in the backlash calc)	0.15 mm

The total pinion shim Stot = measured value + 0.30 mm, then split into S3 and S4 so the distance from ring-gear centre to pinion face equals the factory "E". The total differential shim Stot = measured value + 0.50 mm, split into S1 and S2 to leave the target backlash, using the constant lift of 0.15 mm in the balance. During these measurements the gear carrier and cover bolts are set to a check torque of 25 N·m18 ft·lb.

Tip: Shims come in fixed increments, so measure each candidate shim at several points with a micrometer and check for burrs or damage — only fit shims in perfect condition. A shim that is nominally right but distorted will falsify both the preload and the backlash.

Automatic final drive — Type 087 N

Backlash and bearing preload

The automatic unit uses a Gleason ring-and-pinion with its own, slightly tighter, backlash window and a higher pinion turning torque. Preload here is set by two threaded adjusting rings rather than by selecting S1/S2 shims.

Item	Specification
Ratio	12 : 37 (mark "G 1237", Gleason teeth)
Master gauge Ro	46.60 mm
Ring-gear backlash	0.15 mm to 0.25 mm
Pinion turning torque — new bearings	250 Ncm to 550 Ncm
Total turning torque (all four bearings)	at least 40 Ncm above the pinion-only turning torque

As on the manual unit, the four backlash readings must not differ by more than 0.05 mm, and these figures apply to a new ring-and-pinion set; for a re-used set, restore the backlash to its previous value as closely as possible. If a new set's backlash falls outside the window, correct it by turning both adjusting rings evenly — do not change the bearing preload to chase backlash.

The pinion shim maths

The pinion shim behind the head is S3 = e − r; the shim opposite is S4 = Stot − S3. The total pinion shim is built up from the dial reading plus three fixed allowances:

Component of Stot	Value
Installed setting shim	1.1 mm
Bearing preload allowance	0.15 mm
Bearing settling allowance	0.10 mm

So Stot = dial reading + 1.1 mm + 0.15 mm + 0.10 mm. The pinion bearing inner races are heated to about 100 °C212 °F and pressed on with roughly three tonnes of force during assembly. After the shims are fitted, the dial gauge — read in the red range — must show the ring gear's etched deviation "r" within ±0.04 mm.

Final-drive oil & level check

On the manual car the final drive shares the gearbox housing and the same fill, so its oil is covered by the manual transmission data. On the automatic car the final drive is a separate reservoir from the ATF and is checked on its own.

Item	Specification
Capacity (automatic final drive)	approx. 1 L1.1 qt
Oil	hypoid gear lube SAE 90, API GL5 (or MIL-L 2105 B)
Filler-plug torque	20 N·m15 ft·lb

To check the level, clean around the filler plug and unscrew it. With the car on a level surface, the oil should reach the lower edge of the filler opening. Clean the plug, refit it and tighten to the torque above.

Tightening torques — Type 087 N final drive

Torque values for the automatic final drive and its central-tube driveline. Imperial values toggle from the metric figure shown.

Final drive

Fastener	Thread	Torque
Flanged shaft to differential	M 8 x 1.25	25 N·m18 ft·lb
Lockplate to adjusting ring	M 6 x 1	8 N·m6 ft·lb
Pinion-shaft cover to final-drive case	M 10 x 1.5	42 N·m31 ft·lb
Final-drive cover to case	M 8 x 1.25	25 N·m18 ft·lb
Ring gear to differential	M 10 x 1	78 N·m58 ft·lb to 93 N·m69 ft·lb
Automatic transmission to final drive	M 8 x 1.25	29 N·m21 ft·lb
Drive shaft to transmission flange	M 8	42 N·m31 ft·lb

Central tube & converter driveline

Fastener	Thread	Torque
Converter bearing to rear bell housing	M 8 x 25	21 N·m15 ft·lb
Drive shaft to flanged shaft	M 10 x 46	80 N·m59 ft·lb
Central-tube flange to clutch bell housing	M 10 x 35	42 N·m31 ft·lb
Central-tube housing to transmission case	M 12 x 80	85 N·m63 ft·lb
Central-tube housing to transmission case	M 10 x 50	42 N·m31 ft·lb
Converter to drive plate	M 8 x 11	40 N·m30 ft·lb
Drive shaft and damper	M 10 x 46	80 N·m59 ft·lb
Damper to flywheel	M 8 x 40	21 N·m15 ft·lb
Cover to clutch bell housing	M 10 x 25	42 N·m31 ft·lb
Support to transmission	M 10 x 30	42 N·m31 ft·lb
Hook to central tube	M 8	20 N·m15 ft·lb