Lotus Esprit GearBoc
Discussion
I have a 1985/6 NA esprit. The input shaft retaining circlip has failed and i therefore need a new input shaft, got that and other bits, firstly does anyone know if when i take the bellhousing off is the gearbox will the fluid spill out. Also reading the vehicle serviceing notes it seems very straight forward inserting a new Input shaft has anyone tried this and is it as simple as the book makes out.
1 Remove bellhousing
2 Insert shaft
3 Fit circlip
4 Replace bellhousing
Cheers in anticaption
C100CBK
1 Remove bellhousing
2 Insert shaft
3 Fit circlip
4 Replace bellhousing
Cheers in anticaption
C100CBK
That leaves out a few potential pitfalls.
Removing the bell housing does open up the end of the gearbox, so yes, the oil could spill out. You could get by with standing the gearbox on it's tail during the operation, but it would be less grief to simply drain the gear oil before starting. Gear oil should be changed periodically anyway, just like engine oil. Now would be a good time to do so.
Prepare yourself for the possibility that it will be worse.
Have you removed the transaxle yet? How does the end of the engine's crankshaft look? Are the internal splines in the end of the primary shaft intact (the shaft inside the gearbox that the input shaft fits into)?
If the input shaft moved forward far enough to disengage the splines, then it's VERY unlikely that it did so without damaging the end of the crank. Replacing the input shaft and spigot bearing without repairing the crank would be folly. Repairing the crank would require removing it from the engine. By the time you have done that, you're well into a bottom-end engine rebuild, so you may as well finish it.
When the circlip fails and the spring-loaded clutch/ input shaft moves forward, the depth of the spline engagement with the primary shaft diminishes until there isn't enough tooth contact area to transmit the torque... and the spline strips.
If the clutch/ input shaft's spline is stripped, then you can count on the primary shaft's internal spline being partially stripped as well. If the primary shaft's internal spline is damaged, then the primary shaft has to be replaced as well. Doing that will require opening the body of the gearbox and partially dismantling it to replace the shaft. At which point you may as well replace the 3-4 synchro rings and inspect some bearings while you're in there.
If you are fortunate and only have to replace the clutch input shaft as you noted, then simply removing & replacing the existing parts is all that is necessary.
When you remove the output shaft housings from the sides of the gearbox, you will find spacer rings inside. Note where they come from and their order. Put them back exactly where you found them. Do NOT mix them up.
There are paper gaskets between the output shaft housings and the gearbox... order new ones. Seal them with Permabond A-136 or MH196, Loctite 515, 518 or 574, or Permatex Anaerobic Gasket Maker (Loctite 518 private labeled). The manual recommends using a silicone sealant, and it will work, but the other products are superior. In the UK, A-136 is probably more readily available at retail. In the USA, Permatex 518 is easier to find.
There's a tube/ tunnel that surrounds the input shaft as it passes through the area that houses the differential. It's sealed on either end by two O-rings that will have to be replaced. No big deal, but order them.
Replace the spigot bearing (pilot bearing). The release bearing (throw-out bearing) is expensive enough to ponder a bit before replacing it, but I strongly suggest that you do so despite the cost.
That's all you "need" to do. But it ignores the opportunity to check and adjust the pre-load in the differential support bearings as well as the ring & pinion backlash. Taking care of those tasks increases the degree of difficulty significantly, but it would be better to do so while you're in there rather than waiting til later and doing it all over again.
If the crankshaft is damaged, have the spigot bearing pocket re-machined to accept a ball bearing in place of the OEM needle bearing. The ball bearing will better support the input shaft and prevent the circlip/ spring loaded input shaft from ever being a problem again. PM me if it comes to that and I'll forward detailed directions.
Regards and good luck,
Tim Engel
Removing the bell housing does open up the end of the gearbox, so yes, the oil could spill out. You could get by with standing the gearbox on it's tail during the operation, but it would be less grief to simply drain the gear oil before starting. Gear oil should be changed periodically anyway, just like engine oil. Now would be a good time to do so.
Prepare yourself for the possibility that it will be worse.
Have you removed the transaxle yet? How does the end of the engine's crankshaft look? Are the internal splines in the end of the primary shaft intact (the shaft inside the gearbox that the input shaft fits into)?
If the input shaft moved forward far enough to disengage the splines, then it's VERY unlikely that it did so without damaging the end of the crank. Replacing the input shaft and spigot bearing without repairing the crank would be folly. Repairing the crank would require removing it from the engine. By the time you have done that, you're well into a bottom-end engine rebuild, so you may as well finish it.
When the circlip fails and the spring-loaded clutch/ input shaft moves forward, the depth of the spline engagement with the primary shaft diminishes until there isn't enough tooth contact area to transmit the torque... and the spline strips.
If the clutch/ input shaft's spline is stripped, then you can count on the primary shaft's internal spline being partially stripped as well. If the primary shaft's internal spline is damaged, then the primary shaft has to be replaced as well. Doing that will require opening the body of the gearbox and partially dismantling it to replace the shaft. At which point you may as well replace the 3-4 synchro rings and inspect some bearings while you're in there.
If you are fortunate and only have to replace the clutch input shaft as you noted, then simply removing & replacing the existing parts is all that is necessary.
When you remove the output shaft housings from the sides of the gearbox, you will find spacer rings inside. Note where they come from and their order. Put them back exactly where you found them. Do NOT mix them up.
There are paper gaskets between the output shaft housings and the gearbox... order new ones. Seal them with Permabond A-136 or MH196, Loctite 515, 518 or 574, or Permatex Anaerobic Gasket Maker (Loctite 518 private labeled). The manual recommends using a silicone sealant, and it will work, but the other products are superior. In the UK, A-136 is probably more readily available at retail. In the USA, Permatex 518 is easier to find.
There's a tube/ tunnel that surrounds the input shaft as it passes through the area that houses the differential. It's sealed on either end by two O-rings that will have to be replaced. No big deal, but order them.
Replace the spigot bearing (pilot bearing). The release bearing (throw-out bearing) is expensive enough to ponder a bit before replacing it, but I strongly suggest that you do so despite the cost.
That's all you "need" to do. But it ignores the opportunity to check and adjust the pre-load in the differential support bearings as well as the ring & pinion backlash. Taking care of those tasks increases the degree of difficulty significantly, but it would be better to do so while you're in there rather than waiting til later and doing it all over again.
If the crankshaft is damaged, have the spigot bearing pocket re-machined to accept a ball bearing in place of the OEM needle bearing. The ball bearing will better support the input shaft and prevent the circlip/ spring loaded input shaft from ever being a problem again. PM me if it comes to that and I'll forward detailed directions.
Regards and good luck,
Tim Engel
Edited by Esprit2 on Sunday 15th April 00:06
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