Rear Main Seal Replacement

Rear main seal replacement with the gearbox removed, best done alongside a clutch so the same labour is not paid twice.

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Service Info

Typical Duration 5 hours

We confirm the rear main seal rather than the gearbox input seal or sump gasket is leaking, remove the gearbox, replace the seal fitted square and to depth, check the crankcase breather and crankshaft surface, renew the clutch where sensible and refit.

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6-month, 6000km warranty

The Most Trusted Rear Main Seal Replacement

The rear main seal sits where the crankshaft leaves the back of the engine, between the block and the flywheel. It is a simple seal in an awkward place: reaching it means removing the gearbox, which is why a small oil leak here costs what it does. The classic sign is oil dripping from the bellhousing area, often mistaken for a gearbox leak. Michanic diagnoses and replaces rear main seals with the gearbox out.

Why Choose Our Rear Main Seal Replacement Services?

  1. Leak Source Confirmed:
    Oil at the bellhousing can be the rear main seal, the gearbox input shaft seal, or the sump gasket. Each needs different work.
  2. Clutch Done Together:
    The gearbox is out either way. Renewing the clutch at the same time avoids paying that substantial labour twice.
  3. Clutch Protected:
    Oil from this seal contaminates the clutch friction plate and causes slip and judder, so the leak is worth fixing before it does.
  4. Honest Scope:
    You are told this is a gearbox-out job before it starts, not once the car is already apart.

Why We are the Best Choice for Rear Main Seal Replacement

  • Breather Checked:
    A blocked crankcase breather pressurises the engine and pushes oil past a brand new seal exactly as it did the old one.
  • Crankshaft Surface Inspected:
    A groove worn by the old seal will leak past a new one unless it is addressed during fitting.
  • Fitted Square and to Depth:
    The seal is installed with the correct tool, since a seal driven in crooked leaks immediately.
  • Flywheel Assessed:
    With access open, the flywheel surface and, on dual mass units, its condition are checked while it is off.

The seal itself is inexpensive; its location is what matters. Because the gearbox has to come out, this is a job you want to do once, which is why the clutch, the release bearing and the flywheel are all assessed while everything is apart. There is a second reason not to leave it: oil escaping from this seal lands directly on the clutch friction plate, and an oil soaked clutch slips and judders. Left long enough, a cheap seal ruins a clutch and you pay for the same gearbox removal twice.

Frequently Asked Questions

  • Why is a small seal such an expensive job?
    Because of where it is. The seal sits between the engine and the gearbox, so the gearbox has to be removed to reach it. The part costs very little and the access is essentially all of the cost.
  • Should the clutch be replaced at the same time?
    If the clutch has covered significant mileage, yes. The gearbox is already out, so fitting a clutch then costs only the parts, whereas doing it later means paying the same removal labour a second time.
  • Is the leak the rear main seal or the gearbox?
    Both leak into the same area, which is why it is often misattributed. Engine oil and gearbox oil differ in colour and smell, and the drip point is examined carefully before the gearbox comes out.
  • Why did my rear main seal fail?
    Age hardening is the usual cause, often accelerated by a blocked crankcase breather pressurising the engine. A groove worn into the crankshaft by the original seal also causes a replacement to leak early.
  • Can I just keep topping up the oil?
    It is a poor idea. Beyond the ongoing loss, oil reaching the clutch plate causes slip and judder, so what begins as a seal leak ends up costing a clutch and the same gearbox removal anyway.