No go forward, only reverse

I'm out of country, but my son has been keeping my SIII running. He now tells me that, in the course of parking it at a store, he experienced a sort of "bang" when maneuvering. After that, he had no forward gears (just some whirring), but he still had reverse. So he got the Rover home by reversing it the mile or so back, where it now sits. My initial thought was the transfer had slipped into neutral, but that doesn't explain the existence of reverse only. What am I likely facing when I get back?

No forward in only 1st gear or any forward gear? I would think it highly unlikely that a transfer case issue could create the described symptoms. More likely in the trans with first gear.

Seems not much will be known for sure until you dig in to the transmission. Doesn't sound good...

'99 Disco II
'76 Series III Hybrid 109
'95 R.R.C. Lwb (Gone...)
'70 Rover 3500S (Gone...)

Here's an update now that I am with the Rover: I can change gears as normal, but all I get is a whirring from the transmission. However, the whirring is aligned to the gear I am in (1st is low, 3rd is high), so I think the mainshaft is turning with the proper gears. I am guessing that somehow the mainshaft is disconnected from the drive line - but it does work in reverse. I will take off the overdrive and check the mainshaft nut for a start. I've no other ideas that I can come up with.

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Originally Posted by ybt502r

Here's an update now that I am with the Rover: I can change gears as normal, but all I get is a whirring from the transmission. However, the whirring is aligned to the gear I am in (1st is low, 3rd is high), so I think the mainshaft is turning with the proper gears. I am guessing that somehow the mainshaft is disconnected from the drive line - but it does work in reverse. I will take off the overdrive and check the mainshaft nut for a start. I've no other ideas that I can come up with.

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Time for the Tear down. You will know it when you see it. Check splines on the end of shafts, sheared gears, you know the drill, bits of metal in 90w, etc.

I've pulled the overdrive (Fairey). The OD gear on the mainshaft is worn/stripped, so there is no purchase when engaging the transmission. No obvious issues other than wear over the last 18 years. No bits in the oil. There are just enough ridges of the teeth left that when reverse is used, the shift of the mainshaft is enough to maintain a connection to the transmission. The mainshaft nut is lose, obviously, too.

Time for an OD rebuild or a new design - I've opted for a different design, so I'm going with a Roamerdrive.

UPDATE: I installed a Roamerdrive, replaced all the fluids, and upgraded the transfer cover (thanks Roamerdrive too) while at it. The SIII is back on the road. The Fairey was just worn out between its mainshaft gear and where it engages in the OD unit. Installing the Roamerdrive was straightforward, though it took more fiddling than I expected to get the lever in the right place and all the floor set right. It is quiet from the start, though I am getting familiar with how to shift it properly (take your time!). It's a solid unit, and as an added benefit, I don't have to deal with the castellated mainshaft nut any more.