failed overdrive

halfpenny · Post by **halfpenny** » Thu Apr 25, 2019 5:35 pm

Came off the bypass at 70, but no drive at the roundabout as I took a flyer in o/d third. Coasted for a bit then found seemingly normal drive with o/d engaged. Got home a few more miles without messing with the o/d, and managed to pull away from rest a couple of times. My o/d inhibit only works in reverse, so o/d works on all forward ratios, but I usually remember to disengage o/d for first and second.
Now, no drive in first or reverse with o/d disengaged - from the noise,something obviously slipping in the o/d. My suspicion is that the sprag clutch has failed. Before I begin, has anyone experience of loss of drive in forwards AND reverse? There was no reverse inhibit when I bought the car several years ago, so the o/d may have been damaged by a previous owner I guess.
It looks possible to get the gearbox and o/d off the bell housing (2 rod box and LH o/d) by removing the gearbox cross member. Could someone confirm. I have access to a vehicle lift, so removal from below is my favoured option.
Many thanks.

Post by **philhoward** » Thu Apr 25, 2019 5:56 pm

It can be removed from the bellhousing on its own although I think you need to support the engine (as its third mounting is the gearbox).

Sounds like the clutch has indeed failed in the OD..

I don't think it will take a lot of abuse in 1st or 2nd (in 1st it usually needs to build up pressure from the pump first) but it doesn't like overdrive in reverse at all. I also had no inhibitor on mine for a while (albeit a J-type, but it's the same principles inside) and forgot to disengage it once or twice when engaging reverse and got a very unhealthy noise when I tried to let the (normal) clutch out until I spotted by tell-tale lamp still on..

halfpenny · Post by **halfpenny** » Thu Apr 25, 2019 7:04 pm

Thanks Phil. I have a tell tale lamp for the same purpose. Looks like gearbox out tomorrow and a trip to Dave Twigger at Overdrive Services in Rugby- fortunately just down the road.

Post by **b.c.flat hat** » Thu Apr 25, 2019 7:57 pm

Here's mine.

: IMG_0974.JPG (250.01 KiB) Viewed 885 times

halfpenny · Post by **halfpenny** » Fri Apr 26, 2019 5:33 pm

Thanks for the photo. Quite straightforward and out this morning. BTW, drained weight of gearbox and o/d is 45Kg. It looks as if the bell housing will come off for clutch inspection - anyone say no?

Post by **peter freeman** » Fri Apr 26, 2019 6:01 pm

If its a two rail box then the GB comes off easily then as you say you can take the bell housing off the look at/change the clutch - did mine a couple of years ago - six bolts hold the GB on to the bell housing.

halfpenny · Post by **halfpenny** » Fri Apr 26, 2019 6:19 pm

Thank you Peter. A job for tomorrow.

Post by **peter freeman** » Fri Apr 26, 2019 8:39 pm

I am nearly ready to take the engine out of our Coupe - I am almost certain the flywheel needs a new starter ring even though it looks ok through the starter hole. Three different starters have failed to turn the engine - very frustrating.

halfpenny · Post by **halfpenny** » Sun Apr 28, 2019 5:58 pm

Bell housing off and clutch checked - like new, so a bonus. Two points of interest. A hardened thick washer between the clutch fork and its pivot post on the bell housing, and no external return spring for the clutch fork. The latter seems a strange omission, but there is no hole to hook a spring in place.

Post by **Oldconn** » Sun Apr 28, 2019 8:21 pm

Mine is the same. Ford had a spring on the Cortina , but Reliant didn't on the Scimitar. I don't know why.

halfpenny · Post by **halfpenny** » Wed May 08, 2019 12:04 pm

Just to close this off, turned out that the outer ring of the one way clutch was spinning in the casing - hence no drive. New oversize ring fitted as part of a full rebuild, so all will now be well.