The Dg 300 Mark 2 5-Speed Transaxle Gearbox Unit
Total Page:16
File Type:pdf, Size:1020Kb
THE DG 300 MARK 2 5-SPEED TRANSAXLE GEARBOX UNIT The Mark 2 DG300 Gearbox has five forward casings in magnesium alloy. ratios and reverse. It is designed for use The differential is of Limited Slip design, with rear engine competition cars having a capacity of up to 4% litres. the unit normally supplied being the Cam and Paw1 type. Only one final drive ratio is used. Since the The gearbox unit is lubricated by oil splash, drive is indirect at all times, any change in and the final drive by pump. The pump is ratio can be made through the gearbox. The located in the main case, and is fed via a drive is taken from the clutch shaft to the filter which can be withdrawn from the out- spiral bevel final drive via straight cut side of the case. The oil is piped out of the gears. Gear change is effected by non-syn- main case on the righthand side and returns chronised face dogs. Ratios can be changed via external piping, thus providing for the without removing the unit from the chassis, fitting of an oil cooler. The latter is strongly and all requirements can be met from our recommended to ensure that oil temperature extensive range of gears. All ratios except does not exceed its maximum of bottom are inter-changeable, and may be arranged in any order. The gear change rod is mounted low down on The differential and crown wheel assembly the right hand side. The clutch is operated is mounted on two taper roller bearings by steel. fork and push-rod - accepted as the located in the side plates and adjustable to simplest and most reliable system, es- correct pre-load by shins. Output shafts are pecially with monocoque chassis. The push- also mounted in the side plates, and lip oil rod is actuated from a slave cylinder mounted seals are fitted. on the side of the main case. The gears run directly on caged needle roller The general configuration of the DG 300 bearings, and each gear and bearing revolves Mark 2 Series provides the maximum utilisa- as an assembly. Heat treated nickle-chrome tion of power allied to minimum weight for steel is used for all gears and shafts. Selec- the power required to be transmitted. tor forks are cast in aluminium bronze, and Technical Specification Oil Filler Gear rod movement .225 either side of neutral for forward gears. forward for reverse Gear rod rotates total. 2 4 35 Oil 4.300 0 of gear i Dimensions in inches 2 Index PAGE PAGE Backlash, adjusting . 15, 16 Main case and Diff. Compartment 9 Bearing Carrier (Main) . 5 Oil, capacities and type . 3 Bearing Carrier (Clutch Shaft . 9 Oil pump . .. 13, 18 Bearings Oil Filter . .. 8, 13 Layshaft and pinion, front 9, 15 .. 9, 13, 15 Layshaft and pinion, tail 5 Pinion . - . Plungers . .. 5 Clutch Rings . 5 .. 15 Clutch Shaft . 9 pre-load, adjusting . Crown Wheel . 13, 15 Reverse Idler Gear . .. 9 Crown Wheel & Pinion, setting up 15 Seleetor Finger . .. 5, 9 Differential Unit, Removal 9 Selector Forks, removal . .. 5 Differential Unit, Dismantling 13 Selector Forks, setting up .. 7 Selector heads . .. 5, 7 End Case . 5 Selector Rods . .. 5, 7 Filter . 13 Setting up + Gearbox Unit . 5 Crown Wheel & Pinion . 15 Gear Ratios, changing . 5 Selector Forks . 7 Side Plates, removal . 9 Hubs . 5, 7 Side Plates, Dismantling . 13 Layshaft . 7 Technical specification . 2 General notes on maintenance and overhaul Only genuine Hewland spares should be When warming the outside of the case, keep used as replacements. These are manufac- the blowlamp moving. Do not overheat. Test tured in our own workshops to the fine with a spot of moisture, which will bounce tolerances necessary, and rigorously inspect- off when the case is hot enough. ed and tested: When refilling with oil, put half the quantity New nuts and gaskets should always be into each filler hole. Never put all the oil in used on re-assembly. one oil sump. DG 300 Mark 2 Weight 118 lbs Oil Capacity 3% pints Type of Oil S.A.E. 80 or 90 ‘f;... 3 The Gearbox unit REMOVING THE UNIT ened layshaft nut and remove the layshaft from 7. Undo the three allen cap screws (36) and the bearing carrier. Gears are exchanged in pairs take out the to Selector Rod Springs and END COVER - one from the layshaft and one from the pinion balls (35 & 34 ). Then take out the three shaft. Each gear is etched with two sets of Selector Rods, one at a time, followed by the 1. Remove the eight 5/16 UNF Nyloc nuts and numbers. The first is the number of its own bottom balls and springs. washers from the end cover. Take off cover teeth. The second is the number of teeth on its and gasket. mating gear. 8. Undo the 3/8 UNC allen ca screw (44) and push out the locking slugs. ( 43) 2. Remove the split pins from the castellated It is essential that gears should be correctly pinion and layshaft nuts. paired according to these numbers. 9. Inspect pinion and layshaft tail bearings and renew if necessary. To remove, warm up 3. Push the heads of the two outside selector surrounding area. N.B. In layshaft bearing rods, thus engaging the gears. This locks the STRIPPING THE GEAR TRAIN check for wear on steel sleeve in layshaft gear box by engaging 2 gears. bearing and renew if necessary. 1. Remove hubs, clutch rings and gears. Wash 4. Remove the pinion nut, (left hand thread) and and inspect for wear and cracks, giving part- Re-assemble in reverse order to above, subject slacken off the lay shaft nut, (conventional icular attention to the clutch rings. to the following:- right hand thread) 10. When replacing bottom balls and springs, set Examine forks for heavy or uneven wear, and 2. up to correct height. About one-third of the test for excessive play between forks and 5. Now withdraw the two outside selector rods, ball should be exposed. Continue by inserting clutch rings. to disengage the gears. locking slugs and selector rods, then top balls and springs. 3. If forks are not to be stripped, check that nuts are tight and properly tabbed. Continue BEARING CARRIER ll.Any hub renewed should be identical in stripping. length with the original. If replacing all hubs, 1. Remove the ten 5/16 UNF nuts and or main bearing carrier, check that overall _- __ _ washers. _ TO REMOVE SELECTOR FINGER HOUSING (5) length of pinion assembly has not been alter- ed. Clearance is essential to avoid overheat- Using a plastic mallet, tap the bearing carrier 2. 4. Remove selector finger housing by:- ing and seizure, but too much clearance will and remove it from the main case, complete cause excessive wear. with lay-shaft assembly and gear train. Sup- (I) Remove bung, spring and plunger, (16, port the gears, hubs and clutch rings with 17, 18) from the selector fin er housing the hand, as they come off the pinion. and withdraw selector finger. (38) (2) Undo 5/16 UNC Allen cap screw The gearbox unit is now completely removed. (3) Undo 5/16 UNF Nyloc nut inside housing Replace in reverse order to above. 5. Remove gasket from bearing carrier. CHANGING GEAR RATIOS 6. To remove forks, knock back ‘locking tabs (52) and undo nut (53). Remove all three sets When changing a gear ratio, take off the slack- and lift off forks (49, 50, 51). Setting up the selector forks - overleaf 5 GEARBOX PARTS LIST ILLUS. ILLUS. DESCRIPTION QTY PART NUMBER DESCRIPTION QTY PART NUMBER No. No. Not illus Gearbox Complete Std I DC300 A26 Hub Centre I DG227 Not illus Gearbox Complete Alternator Drive I DG300A A 2 7 Hub Rear I DG228 Al 5/16" UNF Nyloc Nut 30 FT20I 3 A28 Inner Track 5th Gear I DG229 A2 5/16" Flat Washer 30 FT2027 A 2 9 Thrust Washer I DG2294 A3 End Cover I DG204 A 3 0 Stud I FT2025 A 4 Gasket End Cover I DG260 A31 Bearing 2 DG229 I A32 A 5 Selector Finger Housing I DG203 Nut I DG230 A 6 Gasket Selector F inger I DG261 A 3 3 Spacer I DG203 IO A 7 Nut Layshaft A 3 4 Balls : Steel I DG236 6 FT202 I A8 Split Pin 2 DG2302 A35 Spring 6 FT2022 A 9 Bearing Layshaft I LG2343 A 3 6 Screw 3 FT 2023 AI0 Bush I LG2292 A37 Screw I FT203 I I Al I Stud 7 FT2026 A 3 8 Selector Finger I FT252 A l 2 Bearing Carrier I DG202 A39 Bush 5/8” 2 FRO36 Al3 Screw I FT203 A40 ‘0’ Ring I FT2037 1 A l 4 Spring A41 I Plate FT2034 I FT2038 A42 AI5 Ba I I I FT2033 Screws- 4 FT2039 A l 6 Plunger I DG2030 A43 Plungers 2 FT2024 Al7 Spring I FT2032 A 4 4 Screws I FT2028 A l 8 Plug I FT2035 A45 Selector Rod 1st & Reverse I DG246 A l 9 Thrust Washer I DG2345 A46 Selector Rod 2nd /3rd I DG247 A20 A47 Spacer I DG2346 Selector Rod 4th/5th I DG248 A48 A21 Layshaft Std I DG234 Adjusting Spacer 3 FT2463 A 4 9 Selector Fork I St/Reverse A21 Layshaft with Integral 1st Gear I DG234A I DG249 A 5 0 Selector Fork 2nd/3rd A22 Reverse & First Sliding Gear I DG23 I I DG250 A23 Hub Front I DG226 A51 Selector Fork 4th/5th I FT25l A24 Needle Bearings 5 DG226 I A 5 2 Tab Washer 3 FT2461 A25 Clutch Ring 2 DG232 A53 Nut 3 FT2462 THE GEARBOX UNIT (continued) SETTING UP THE SELECTOR FORKS (b) The clutch ring should engage fully with either gear.