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Hewland NMT Servicing Instructions

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SERVICING INSTRUCTIONS AND ILLUSTRATED
PARTS LIST FOR HEWLAND NMT GEARBOXES
HEWLAND ENGINEERING LTD
WALTHAM ROAD, WHITE WALTHAM,
MAIDENHEAD, BERKSHIRE,
SL6 3LR, ENGLAND
Last Update 10th July 2012
© Copyright Hewland Engineering Limited
PAGE 1

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Summary of Contents for Hewland NMT

  • Page 1 SERVICING INSTRUCTIONS AND ILLUSTRATED PARTS LIST FOR HEWLAND NMT GEARBOXES HEWLAND ENGINEERING LTD WALTHAM ROAD, WHITE WALTHAM, MAIDENHEAD, BERKSHIRE, SL6 3LR, ENGLAND Last Update 10th July 2012 © Copyright Hewland Engineering Limited PAGE 1...

  • Page 2: Table Of Contents

    Differential bearing preload Differential Options Pinion shaft mounting Illustrated Parts List Pinion shaft bearing preload Gearbox Tooling Crownwheel backlash setting General Technical Bulletins Sequential barrel setting Oil system layout Gearbox assembly Recommended Tightening Torques © Copyright Hewland Engineering Limited PAGE 2...
  • Page 3 Pinion Shaft Assembly fig.4 Crownwheel setting fig.15 Selector Assembly fig.5 Sequential barrel setting fig.16 NLT-218-Tripod Assembly fig.6 Powerflow diff assembly fig.17 Gearbox Tooling fig.7-10 Differential Assemblies 15-21 fig.18 Oil system layout fig.11 Differential Subsidiary Parts © Copyright Hewland Engineering Limited PAGE 3...

  • Page 4: Technical Specification

    TECHNICAL SPECIFICATION The NMT gearbox is a transaxle unit, designed for mid-engined, rear wheel drive cars. The unit is produced with six forward gears, reverse, and a powerflow differential. The gear selection mechanism is sequential, with a separate, mechanically interlocked reverse engagement mechanism.

  • Page 5: General Notes

    Thoroughly clean and inspect all parts before reassembly. Discard any worn or damaged components and replace with new ones. Use only genuine Hewland parts as replacements. These are manufactured in our workshops to the fine tolerances necessary and are rigorously inspected.

  • Page 6: Differential Bearing Preload

    PART No. RATIO MOUNTING ITEM (90) ITEM (91) DIST NMT-221-AW 11/31 2.316” FGC-206-2A NMT-205-2 NMT-221-BW 10/31 2.316” FGC-206-2A NMT-205-2 NLT-221-CW 9/35 2.200” FGC-205-2A NMT-205-2A FIGURE 1 © Copyright Hewland Engineering Limited PAGE 6...

  • Page 7: Pinion Shaft Mounting

    Note: It is not correct practice to replace a pinion FIGURE 2 shaft without measuring the setting distance, even if the old and new shafts have the same calibration. © Copyright Hewland Engineering Limited PAGE 7...

  • Page 8: Pinion Shaft Bearing Preload

    SK-1913 Fitting a longer six gear spacer (14) will de- crease the pinion bearing preload, whereas shortening the six gear spacer (14) will increase the pinion bearing preload. FIGURE 3 © Copyright Hewland Engineering Limited PAGE 8...

  • Page 9: Crownwheel Backlash Setting

    Note: Dummy are used so that it is easy to change the shims during the setting procedures. Before fitting the actual diff bearings, it is important compare thier width with that of the dummy bearings and compensate the shims accordingly for any difference. FIGURE 4 © Copyright Hewland Engineering Limited PAGE 9...

  • Page 10: Sequential Barrel Setting

    Any difference between the odd & even gear measurements must be corrected by replacing the barrel spacer (26) with one of the correct thickness. FIGURE 5 Note: It is not possible (or necessary) to individually adjust each fork. © Copyright Hewland Engineering Limited PAGE 10...

  • Page 11: Gearbox Assembly

    Fit the pinion shaft as described previously. Hold the reverse selector fork (31), with reverse pinion gear (121), in position in the bearing carrier (2). Slide the reverse selector shaft (110) into place and secure with screw (122). © Copyright Hewland Engineering Limited PAGE 11...
  • Page 12 Note : If the oil pump is fitted, the diff assembly must be removed from the maincase to allow the clutch shaft to be fitted (or removed). Fit magnetic plug (114) and washer (115) to maincase. © Copyright Hewland Engineering Limited PAGE 12...

  • Page 13: Changing Gear Ratios

    [Some mechanics find assembly easier if the layshaft bearing inner track is pre-fitted in the casing, rather than onto the end of the layshaft.] © Copyright Hewland Engineering Limited PAGE 13...

  • Page 14: Powerflow Differential

    The diagram shows combinations. the stack setup with the maximum 12 working faces. Standard stack may be shuffled to give as few as © Copyright Hewland Engineering Limited 2 working faces. PAGE 14...

  • Page 15: Differential Options

    DGC-212 Diff Assembly (superseded March 2010) FIGURE 7 © Copyright Hewland Engineering Limited PAGE 15...
  • Page 16 DGC-212 Diff Assembly (March 2010 onwards) FIGURE 7a © Copyright Hewland Engineering Limited PAGE 16...
  • Page 17 DGC-212-S Diff Assembly (superseded March 2010) FIGURE 8 © Copyright Hewland Engineering Limited PAGE 17...
  • Page 18 DGC-212-S Diff Assembly (March 2010 onwards) FIGURE 8a © Copyright Hewland Engineering Limited PAGE 18...
  • Page 19 TPT-212 Diff Assembly FIGURE 9 © Copyright Hewland Engineering Limited PAGE 19...
  • Page 20 NLT-212 Diff Assembly (superseded March 2009) IN ORDER TO FIT THE NLT DIFFERNETIAL IN THE NMT BOX, THE NLT SIDE PLATE (NLT-205) WILL NEED TO BE FITTED This differential was superseded FIGURE 10 by the differential shown on the next page.
  • Page 21 Please note that the NLT-201 maincase THESE BOLTS MUST BE FITTED will need to be modified to fit this differ- USING LOCTITE 648 RETAINER ential. Please contact Hewland Engi- AND LOCKWIRE. neering for details. © Copyright Hewland Engineering Limited PAGE 21...

  • Page 22: Illustrated Parts List

    ILLUSTRATED PARTS LIST © Copyright Hewland Engineering Limited PAGE 22...
  • Page 23 FIGURE 11 © Copyright Hewland Engineering Limited PAGE 23...

  • Page 24: Fig.11 Differential Subsidiary Parts

    OUTPUT FLANGE FGC-205-4 OIL SEAL FGC-205-3 BALL BEARING FGC-205-1 TAPER ROLLER BEARING DIFFERENTIAL DIFFERENTIAL DIFF SPACER SIDEPLATE SPACER DIFF SPACER MAINCASE SPACER FGC-206-1# SHIM VG-201-9 SEALING STRIP * See General Technical Bulletin No. 14 © Copyright Hewland Engineering Limited PAGE 24...
  • Page 25 FIGURE 12 © Copyright Hewland Engineering Limited PAGE 25...

  • Page 26: Fig.12 Casings & Associated Parts

    1/4 BSP HEX. HD. PLUG WSH-017 1/4 BSP BONDED WASHER SCR-159 BUTTON HEAD SCREW HP-M-9062 SCREW TE-201-4 COVER PLATE HP-M-9037 BANJIO JOINT HP-M-9038 SEALING WASHER HP-M-9039 BANJIO BOLT DOW-032 DOWEL STU-062 STUD STU-066 STUD WSH-053 DOWTY WASHER © Copyright Hewland Engineering Limited PAGE 26...
  • Page 27 FIGURE 13 © Copyright Hewland Engineering Limited PAGE 27...

  • Page 28: Fig.13 Layshaft Assembly

    LAYSHAFT SPACER TE-234-1 SPACER TE-234 LAYSHAFT BEA-001 ROLLER BEARING NMT-239-13 CLUTCH SHAFT DGB-244-12 BALL BEARING FT-244-11 OIL SEAL DGB-244 CLUTCH SHAFT BRG. HOUSING DGB-244-14 ‘O’ RING DGB-244-10 CIRCLIP DGB-239-0 CIRCLIP VG-224-13 CAP SCREW © Copyright Hewland Engineering Limited PAGE 28...
  • Page 29 FIGURE 14 © Copyright Hewland Engineering Limited PAGE 29...

  • Page 30: Fig.14 Pinion Shaft Assembly

    104-226-1 TE-231 REVERSE PINION GEAR BEA-062 TAPER ROLLER BEARING NMT-228 REVERSE HUB NMT-230-1 LOCKING RING FT-219-1A CIRCLIP NLT-222 TAPER ROLLER BEARING SCR-109 SOCKET CAP SCREW NLT-223-2 SHIM NMT-230 104-226-2 NEEDLE BEARING WSH-036 WASHER © Copyright Hewland Engineering Limited PAGE 30...
  • Page 31 FIGURE 15 © Copyright Hewland Engineering Limited PAGE 31...

  • Page 32: Fig.15 Selector Assembly

    LIP SEAL TE-260-5 BARREL BOLT TE-246-1 REVERSE SELECTOR SHAFT TE-249 REVERSE SELECTOR FORK CIR-033 CIRCLIP TGTA-206-2 SELECTOR RACK STOP HP-M-9042 BONDED WASHER WSH-013 BONDED SEAL VG-201-9 SEALING STRIP HP-M-7018 PLUNGER SCR-046 SCREW HP-M-7018-A SPRING © Copyright Hewland Engineering Limited PAGE 32...
  • Page 33 NLT-218-TRIPOD ASSEMBLY FIGURE 16 © Copyright Hewland Engineering Limited PAGE 33...

  • Page 34: Fig.16 Nlt-218-Tripod Assembly

    Variable Parts © Copyright Hewland Engineering Limited PAGE 34...

  • Page 35: Gearbox Tooling

    Gearbox Tooling FIGURE 17 © Copyright Hewland Engineering Limited PAGE 35...

  • Page 36: General Technical Bulletins

    General Technical Bulletin No. 13 TPT Differential Bevel Gears In line with Hewland Engineering’s constant quest to improve and develop its products, the TPT differential bevel gears have been redesigned to improve the tooth strength and smoothness of operation. In order to identify the new designs, all variations of the TPT gears cut to the revised specification will have a “D” suffix in the part number.
  • Page 37 NMT Technical Bulletin No.001 POSITION OF GEAR INDICATOR POTENTIOMETER © Copyright Hewland Engineering Limited PAGE 37...

  • Page 38: Oil System Layout

    23 March 2004 NMT OIL SYSTEM LAYOUT SEE HYD-041 FOR OIL SYSTEM PIPEWORK KIT REFERENCES. (OIL COOLERS ARE NOT INCLUDED.) FIGURE 18 © Copyright Hewland Engineering Limited PAGE 38...

  • Page 39: Recommended Tightening

    (Where Specific component thread details are similar to General nut and bolt details, the tightening torques listed in this section must be adhered to for these components.) The tightening torques for specific components within the gearbox are given on page 4 © Copyright Hewland Engineering Limited PAGE 39...
  • Page 40 Manual Modification History DATE MODIFICATION 21/10/2011 Page 40 added Page 25 & 26 - Item 127 updated and item 143 added 10/07/2012 Page 33 - Figure 16 updated to show latest parts © Copyright Hewland Engineering Limited PAGE 40...