JKD 5-Gang Getriebe
All parts needed to rebuild your gearbox are available from Jack Knight Developments or alternatively we can rebuild your gearbox for you.
Jack Knight Developments Ltd
1 Butts Road Industrial Estate
Tel 01483 764326
Fax 01483 769893
THREAD MATERIAL TORQUE LB/FT ALUMINIUM 6 5/16” UNC ALUMINIUM 12 3/8” UNC ALUMINIUM 24 1/4” UNF STEEL 8 3/8” UNF STEEL 40 MAINSHAFT NUT 150 INPUT GEAR NUT 150
No. DESCRIPTION HELICAL S/C SYNCHRO 01
REVERSE IDLER GEAR
REVERSE IDLER BRACKET
REVERSE IDLER THRUST WASHER
REVERSE IDLER THRUST WASHER
REVERSE IDLER NEEDLE BEARING
5TH / REV. BELLCRANK LEVER
OVER SELECT STOP
FORK LOCATING BOLT
REVERSE IDLER SHAFT
- Separate gearbox from engine in the normal way
- Remove the differential side plates, sleeve, o-ring, spring and ball.
- Knock back the tab washers and remove the seven bolts that hold the differential cover, remove the cover and differential from the gearbox.
- To be able to undo both the layshaft and mainshaft nuts you must select two gears, normally 1st and 4th gear. To do this you must clear the selector spool away from the bellcranks by rotating the selector finger 180 degree and pulling the selector finger and spool as far out of the box as you can until the spool hits the case (Fig 4.1). You can now select 1st and 4th gear by moving the hubs, by hand, into gear.
- Unscrew the K-nut (JK133) from the end of the layshaft at the clutch end of the gearbox and remove the bearing sleeve (151).
- Remove the radiator adapter plate from end cover
- Remove the black bung (68) from the end cover to reveal the layshaft bearing (52) , remove the internal circlip (60) and then from the clutch end tap the layshaft (03) through the gear box and remove from the end plate (16). You can now remove the 5th and Rev cluster (40), spacer (08) and thrust bearing (85) from the gearbox.
- Remove the speedo wheel and pinion covers from the end plate by undoing the relevant screws.
- Undo the five bolts that hold the endplate (16) in position and remove the endplate and 5th gear assembly by tapping around the endplate until the sealant breaks, remove the baulk ring and over select stop. Remove the internal circlip (83) and remove the 5th gear (14) assembly, remove the external circlip (65) from the back of the 5th gear and knock the gear out of the ball bearing.
- To be able to undo the mainshaft nut (38) you will need to refit the layshaft (03) and the bearing sleeve (151) on the clutch end of the gearbox.
- Using a suitable breaker bar and a 1-5/16” socket remove the mainshaft nut (38) Note: Left hand thread. Also if your input gear is still fitted remove this now. Once again remove the layshaft (03) and bearing sleeve (151) from the gearbox.
- Remove the splined sleeve (30) from inside the 5th and reverse hub (132), undo the locking nut and locating bolt on the selector fork (25) and slide synchro hub assembly and fork together out of the gearbox. Remove the baulk ring, reverse gear (10) bearing track, needle bearing and final drive pinion from the mainshaft.
- Remove the oil pickup pipe and the laygear (02) from the gearbox , this is easier if you remove them together, and remove both laygear thrust washers.
- Using a pair of 90 degree external circlip pliers remove the circlip from the end of the reverse idler shaft, slide the shaft out of the case and remove the reverse idler gear, needle bearing and small thrust washer. With an allen key undo the bolt which holds the other thrust washer into position and remove.
- Knock back the tab washers which hold the retainer (116) in place, remove the bolts, retainer, shims and spacer (136).
- Remove the circlip which holds the 1st motion ball bearing in position, then, from inside the box, tap the bearing using a long punch to remove the 1st motion shaft and bearing being careful not to damage the gear, remove the needle bearing and baulk ring.
- To remove the mainshaft bearing there is a special tool, but it is possible to remove it using a long punch. First tap the mainshaft from the 5th gear end as far as it will go so that a gap appears between the 1st gear and the mainshaft bearing (Fig17.1). If you have the correct tool this slides into this gap and you can knock the mainshaft back from the 4th gear end which knocks the mainshaft bearing out (Fig 17.2). If you do not have this tool then use a punch to knock the bearing out, be careful not to hit anything but the bearing ! Once the bearing is out you can remove the mainshaft from the gearbox.
- If the forks need replacing you will have to drive the roll pin out of the 3rd / 4th fork and slide the selector rod out of the gearbox then remove both forks. If you want to remove the 5th / reverse selector rod then you can do this by removing the two bolts on the underside of the gear box and pulling out the two dowels then pull bracket and rod free. Remove the nut from the bellcrank stud and remove bellcranks and spacers (Note the order they are removed in for rebuilding purposes). Remove the selector finger and spool from the gear case.
Dismantling the Mainshaft
- Remove the 1st gear, baulk ring and needle bearing, and remove the 3rd / 4th hub assembly and baulk ring.
- Remove the 1st gear bearing track by lightly tapping the inner part of the 1st / 2nd hub assembly. Remove the hub and baulk ring.
- Using a thin punch or similar tool depress the plunger which locates the 3rd gear thrust washer, rotate the washer until the splines align and the washer can be removed. Remove the 3rd gear, needle bearing, plunger and spring.
- Using two thin tools depress the two plungers simultaneously through the holes in the cone of the 2nd gear and rotate the thrust washer until the splines align then remove the thrust washer. Remove the 2nd gear, needle bearing, plunger and spring.
Reassembling the Mainshaft
- Check all parts are cleaned and worn parts replaced.
- Fit the needle bearing onto the 2nd gear bearing track, slide the spring into the hole fitting a plunger into each side. Slide the second gear over the plungers, you may need to depress them slightly, and onto the bearing, refit the thrust washer depressing the plungers so the thrust washer will slide hard against the gear, rotate the washer until both plungers fall into place.
- Fit the needle bearing onto the 3rd gear bearing track, slide the spring into the hole and refit the plunger, slide the 3rd gear over the plunger, again you may need to depress it slightly, and onto the bearing, refit the thrust washer, depress the plunger so the thrust washer will slide hard against the gear, rotate the washer until the plunger falls into place.
- Refit a baulk ring against the 2nd gear cone, slide the 1st / 2nd hub onto the mainshaft, using a suitable tool tap the 1st gear bearing sleeve into position and fit the 1st gear needle bearing, fit a baulk ring and slide the 1st gear into place.
- Refit a baulk ring onto the 3rd gear cone and refit the 3rd / 4th hub assembly.
- All parts must be clean and worn parts replaced.
- Slide the selector finger inside the spool then refit this assembly back into the gear box.
- Refit the bellcranks (61) back onto the top hat bush in the same order as dismantled, slide this assembly back onto the pin in the base of the gearbox and fit the washer and a new locking nut.
- Slide the 5th / rev selector rod (26) into the bracket (27) and slide this through the 1st motion bearing bore in the case and align holes in the bottom of the case with the holes in the bracket. From the under-side of the gearbox refit the two dowels (90), washers (JK202) and bolts (JK317). The washers and dowels must have sealant around them to prevent leaking and the bolt threads a small amount of loctite.
- Hold the 3rd / 4th selector rod into position and slide the selector rod through the clutch end of the gearbox case and into the fork. Now hold 1st / 2nd selector fork in position and slide the rod through it and into the other side of the case, align hole in the 3rd / 4th fork and fit a roll pin.
6) Refit the mainshaft assembly. From the speedo end slide a mainshaft ball bearing onto the end of the mainshaft and using a piece of tube or similar tap the bearing inside the case. Using a depth micrometer compare the difference between the depth of the bearing and the depth of the retainer and fit shims of the same size to the nearest .001”. Refit the retainer (116), tab washers and bolts, fold the tab washer back. From the clutch end tap the mainshaft so as to return it back to its correct running position. Refit the 1st motion shaft, needle bearing, baulk ring and circlip.
7) Refit the reverse idler thrust washer (42) and the screw (JK303) that holds it in place with loctite, before doing the screw up tight, refit the shaft (140) to check it lines up, then tighten the screw, remove the shaft and refit the other thrust washer (43), align the hole on the back with the pin (84) in the bracket (41), idler gear (20) and needle bearing (56), slide the shaft(140) through all the parts and fit a new circlip (141) onto the end of the shaft.
8) Refit the laygear (02) , thrust washers and oil pick up pipe and check the end float in the laygear. Slide the layshaft (03) through the case from the speedo end and into the laygear and out the clutch end of the case. Fit the bearing sleeve (151) onto the end of the layshaft .
9) Slide the final drive pinion onto the mainshaft, then the reverse gear, bearing , bearing track and baulk ring. Refit the 5th / rev fork (25) and hub assembly (132) together, sliding them both on the mainshaft and selector rod until the hole on the fork lines up with the hole in the selector rod. Refit the locating bolt (94), nut (JK102) and a new star washer (96). Refit the splined sleeve inside the hub and screw the mainshaft nut (LH) back onto the mainshaft, select two gears, as mentioned in the dismantling procedure and torque the nut up. Remove the layshaft. Slide the over selector stop (93), if fitted, onto the selector rod and a baulk ring into the 5th / rev. Hub. Refit the ball bearing onto the 5th gear with a new circlip, and refit this assembly into the endplate with an internal circlip. With a new gasket (46) refit the endplate (16) assembly with the five bolts, use sealant on both sides of the gasket to prevent leakage.
10) Fit the thrust bearing (85). This bearing is made up of three pieces, the ball race and the two thrust washers. The holes in the thrust washers are different, the larger one must go against the case and the smaller on against the spacer (08). Refit the spacer (08) and slide the laygear (40) into the gap. Hold the gear in position whilst sliding the layshaft assembly, remembering spring washer (2213), through the end plate, laygear (40), laygear (02) and case again, you will need to tap the layshaft bearing gently the last couple of inches ,you may damage the circlip on the end of the layshaft if you hit the bearing to hard. Fit an internal circlip (60) inside the endplate double check both circlips (53 and 60) are fitted and located correctly in their relevant grooves then fit a new bung (68).
11) With the sleeve (151) still fitted, refit a new k-nut (JK133)
12) Refit both the speedo wheel and pinion with new gaskets, and refit the radiator adapter plate with a new tapered locking washer.
13) Place the gearbox on its side with the differential opening upper most, run a bead of sealant around the sealing face of the gearbox. Place the differential into position and refit the differential cover. Refit the two short and two long bolts with new tab washers and refit the three smaller screws, don’t over tighten these screws, the differential must be able to move from side to side. Gentle tap the differential from the speedo end of the gearbox as far as it will go until the differential makes contact with the case . Refit the detent sleeve, ball, spring and O-ring, fit the side plate and gasket on the detent side of the differential, as it tightens down it should push the differential back towards the speedo side of the gearbox. With a depth micrometer measure the depth of the bearing on the speedo side of the differential and also measure the lip on the other side plate, the shims required will be this difference plus .007” for the thickness of the gasket and .004” to correctly pre-load the bearings. Fit these shims and side plate, tighten down all the bolts on the differential cover and side plates, knock back the tab washers.