Mitsubishi Delica Owners Club UK™

[Scruffian]

Mk1 2.8 auto, Jasper. Name of Boris. Fails to go backwards when reverse selected - fails to move at all, feels like I'm against a tall kerb. Argh!
This happened just now, after an uneventful 300 mile day, involving a little reversing and much going forwards at 60mph - all in 2 wheel drive.

I came to park at the end of a long day, uphill on a street. There was a little vibration as Boris chugged backwards, then he just stopped, I thought I'd hit the kerb - but no, the aim was good. But no rearward movement, nor on subsequent attempts.
Drives forwards fine, with a little rear axle whine and a passing vibration at about 40mph. Otherwise in fine fettle for an old boy, with 150k miles on the clock.

What could it be? Gearbox, transfer box, rear axle?

[Google]

[andyman]

Helical diff gears are weaker in reverse than forwards - after all, you rarely use much power in reverse compared to motorway speeds. To eliminate the diff as an issue, park in neutral, and with a big stilson wrench or similar, turn the prop shaft in the reverse direction, and see if the van moves backwards.
In most gearboxes, first and reverse use the same pair of gears, but reverse runs them through an extra, idler gear to reverse the output direction.
In first, the gears will be directly aligned with each other on the two shafts, in reverse, they will not be alligned, and will be dependent on the idler to connect them. I suspect it may be this piece of the jigsaw which has malfunctioned. If it is not a shifter linkage, electrical or hydraulic fault, external to the box itself, (try these first), then you'll need to strip it down - if it's an auto, not a job for your average home mechanic or average local grease monkey, usually an auto box specialist working in an ultra-clean environment. I doubt strongly that the problem is in the transfer box, but you could test it first by selecting 4WD diff locked and seeing if it will now reverse. If it does, it suggests that the issue is with the rear drive train, not the main gearbox. You could further investigate by disconnecting the front prop shaft at the diff, and twisting it as before, but with 4WD (diff locked) If the vehicle moves backwards, you know that the rear drive train is unlikely to be the issue, the problem is forward of that, ie in the main gearbox. HTH.
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Andy C L300 Super Exceed - over 100 smiles per gallon!

[Scruffian]

Thanks for all that work you put in there, Andy - I found the problem.
I'm ashamed to admit that it wasn't transmission at all - a brake pad had detached itself from its friction material, then slid down when reversing and wedged in the caliper.
Cheap to fix, well, cheaper than transmission but I'm glad it happened at walking pace!

[andyman]

Glad it was that simple. It tends to happen on vehicles that have been stood, especially outside, for a long time. Rust starts at the join, expands, and slowly splits the friction material off the back plate.  I've had it happen and jam on a drum brake as I set off. And on an Audi I bought which had been stood, over half the pads fell apart when I removed them.
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Andy C L300 Super Exceed - over 100 smiles per gallon!

[Lewis]

It often happens when vehicles are left stood for long periods, with the handbrake left on.
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[Deker]

Yes Lewis, agree with that. When vehicle parked up for a long time, do NOT apply handbrake.
With a Manual/Clutched vehicle, where possible hold the clutch open.

The next sentence for those that do not know the Delica brake system. Volvo had the same system in the 1970's
However In Scruffians case this does not apply, due to handbrake operating on brake drum shoes, not the brake pads.