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MG Midget and Sprite Technical - No 3rd or 4th gear

1971 1275. I rebuilt my own gearbox several years ago and finally got the car going yesterday. 1st & 2nd work just fine but I can't get into 3rd or 4th - I just get unpleasant graunching and kick back from the lever. I'm guessing it's an engine out again thing but could anyone shed light on what might be going on?
I checked the archive but couldn't find anything relating to this.
With thanks in advance.
Simon Fryer

Which parts did your replace?

Does it go into 3rd & 4th without the engine running?

Did you try selecting gears with the 'box on the bench, before you refitted it?
Dave O'Neill 2

Thanks Dave, It's been a while so I'm not sure exactly what I replaced but the lay gear for sure, bearings and synchro rings. I did try selecting gears on the bench and all seemed well. It still seems like I can select the gears at rest.
Simon Fryer

Simon, Assuming you stripped the main shaft (3rd motion) I'm wondering if you remembered to install the synchro rings for 3rd and 4th? Without those, the gears would select at rest but, in motion, you'd have no synchronising and they'd grind and kick back I think. You could try crashing 3rd or 4th in and, if they engage, I may be right.
Bill
W Bretherton

Thank you Bill. That would make sense (although it points to new depths of incompetence for me...). I'll try it out.
SF
Simon Fryer

It is possible to remove the side cover with the gearbox in-situ, so it's easy to check for synchro rings.
Dave O'Neill 2

OK - investigative work to do. Thanks Dave.
Simon Fryer

I was about to edit that to 'relatively easy', but you beat me to it.

Don't forget to drain the oil ;o)
Dave O'Neill 2

Thanks Dave. I find the word easy appears way too often in MG related sentences... and if I could forget the synchro rings I guess it's all too possible that I would forget to drain the oil before removing the side cover.
Simon Fryer

I'd try a few more tests before pulling it again. Maybe something is just stuck from sitting for those years.

I'd try something like: block front wheels, jack up one side of the rear and rest on a sturdy axle stand, with engine off get an assistant to dip clutch and work through the gears with you turning the rear wheels to feel if things rotate smoothly.

If that works jack up the other wheel on another sturdy stand, select 3rd gear, dip clutch and start car, then with revs at idle gently let the clutch in and see if the rear wheels rotate, again if all good try 4th, and then run through the gears. Proceed cautiously, keep revs low and keep clear of rotating wheels!


AdrianR

Thanks Adrian - would be nice to find that the whole lot doesn't have to come out again!
Simon Fryer

Another thought (first of the day for me) would be, if you pull the side cover after draining the oil, check if the shifting fork retention screw is properly seated and locked in place.
Martin

Cheers Martin - it's on my list. Will report back once I've had the chance to investigate.
Simon Fryer

So I got out there this afternoon and tried running the engine and going through the gears. I also removed the gear lever and found that the welch plug at the back of the remote had fallen out. Retrieved it and put it back in...
Main issue in the end seemed to be a sticking reverse detent allowing my cackhandedness to go right across the gate bypassing the 3/4 plane and causing much unpleasantness at the reverse side of things. Attention with a hammer popped it back out and enabled me to run through the gears without pain.
No time to actually get out of the garage today but I hope this may have solved my problem.
Sorry it was so mundane and eternal gratitude for the suggestions. Once I have clear results I'll confirm.
Simon Fryer

This thread was discussed between 19/06/2017 and 24/06/2017

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