Fix Your Td5 Starter Motor
Gary Stretton visits Ashcroft Transmissions to find why an LT77 gearbox imploded
A problematic solenoid pack is often the cause of a failed starter motor but it is an easy, cheap fix
The gearbox featured came out of a 1984 90 fitted with an Isuzu 2.8TD. The vehicle had been bought by my friend. On the half-hour pre-purchase test drive up to 50 mph it ran fine but, as he drove it home at 60 mph the gearbox let go big time, adding considerably to the costs of buying the vehicle.
As with any gearbox, high mileage and general wear and tear makes a rebuild inevitable. Known flaws with the LT77 should always be investigated before buying secondhand. Rule of thumb; unless a rebuild has taken place with bills to prove it, assume an overhaul is required – and budget accordingly.
It was not possible to confirm the exact cause of this gearbox failure. However, it’s likely that low oil level over a period of time, followed by sudden higher speed use from the new owner, combined to produce catastrophic failure to the first motion (input) shaft and the layshaft. In addition, the oil pump drive had sheared in the layshaft. The exact sequence of events is unclear, but a reduced oil level (the unit was half full) will starve internal components, while a sheared pump drive means there’s no oil circulating. There was no early warning of failure, just a sudden increase in noise, and difficulty staying in gear, followed by inability to select gears once the vehicle was stationary. The first part of this guide shows what’s required to fully strip a typical LT77 with a view to rebuilding it. Ashcroft Transmissions can do this in about 30 minutes and make it look very easy, as they are fully equipped with the tooling and knowledge for the task. The first time I stripped an LT77, with improvised pullers, it took a couple of hours and much skullduggery with pullers and a bench press. When rebuilding an LT77, don’t undermine your efforts with false economies. Instead, budget to replace the mainshaft, first motion shaft, all synchros, all bearings and any components out of tolerances. Use recognised bearing brands, not unbranded cheap items. If you hope to tackle this yourself, Ashcroft’s LT77 rebuild kit is excellent value for money and uses quality components.
The sequence here is almost typical of how to dismantle an LT77. However, once the main casing has been removed, the internals can come apart randomly, depending on their condition and what is or isn’t broken. Use a workshop manual and parts catalogue for reference when rebuilding. I found the updated advice from Ashcroft, included here, makes a rebuild much easier because it avoids potentially unnecessary steps.