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MG Midget and Sprite Technical - Downshift to 3rd gear

I am a 1275 guy but recently replaced the clutch and linkage in a 1500. While we were at it, I had the transmission rebuilt. The reverse gear was badly worn and warranted replacement.

The clutch is great and the transmission is fine except that it WILL NOT DOWNSHIFT into 3rd gear without horrible grinding, not double clutching, no matching revs, all bets area off at any speed. It upshifts fairly well from 2nd into 3rd but the choice on the downshift is to use the brakes, lower the speed, go into second and slide easily (enough) into third. This makes driving in hilly areas a challenge. It is workable for city driving.

The oil in the box is 75w-90. The problem did not exist before the rebuild. It looks like an engine-out situation, a dreadful thought after the hours of work trying to get the assembly back into the car. At least it is clean now so removal will not be such a mess.

Otherwise, the engine is strong, smooth idle, clutch has a high bite point. It's that 3rd gear that is really causing frustration.

Could this be a linkage issue or a bad synchro from Moss?
Glenn Mallory

""""Otherwise, the engine is strong, smooth idle, clutch has a high bite point. It's that 3rd gear that is really causing frustration.""""""

Did the clutch have a high bit point before you pulled it ???

My 1st thought is Air in the system, that about how the datsun 5 does if there is some air in the line

My 2nd thought would be a worn, missing, or damaged fork boot, the little rubber sleeve that goes over the clutch fork and is attached to the side of the tranny, if thats at fault that can effect the clutch plate and hamper how the gear is shifted

3rd option... ask santa for beer, lots of beer, cause that lump is coming back out.

Were you the rebuilder of the transmission or was it a shop....if it really was a flaw in the trans and not air in the system or a faulty boot on the clutch fork.....and you had it done professionally, id take iit back for a 2nd look

The dead give away is you said this only started to happen after reassembly not before the teardown, so im thinking whats changed and what is the most common flaw that would mirrior your situation

Prop
Prop and the Blackhole Midget

Sounds like a dodgy syncro to me. I've learn't nowadays that if something is working don't be tempted to replace it with a new part just because you have the opportunity.

I had exactly the same problem but on a 1098. No matter how gentle I could not get it from 4th to 3rd without grateing. 2nd to 3rd was no problem. Initial inspection through the access panel on the gearbox revealed nothing untoward. But once dismantled it was clear 3rd gear synchro was completely destroyed.

Not sure whether your fault is the same but all BL gears work on the same principal. Only the shape and size is different between models.

Hope it's something simpler than that but I'm suspicious the symptoms are identical.

Rob
Rob aka MG Moneypit

The clutch is fine. The problem was wear at all of the pivot points and a deep ridge in the release levers where the bearing had bedded in. Before, the clutch pedal went all the way to the floor and with the replacement takes only a slight push for full engagement (disengagement).

The problem is 4th to 3rd gear. I believe that Rob is correct that it was probably a defective synchro in the Moss kit. The transmission was rebuilt by the local transmission guy we send all of our transmissions and overdrives to. This is the first complaint that has presented itself in the British car circle. When he drove it, he could not keep it from grinding in every gear. Several years driving the Datsun 5 speed has left me with a gentle touch.

Trying to shift from 4th into 3rd is like trying to shift a ribcase from 2nd into 1st going 15 miles and hour. The grind is terrible with no chance for engagement. In other words, apparently no functional synchro at all.
Glenn Mallory

If it's the synchro that's not working, surely you should be able to change from 4th to 3rd by double de-clutching and matching the revs as you would on a crash box?
If you can't then I would suspect something else is amiss in the 'box.
Peter Blockley

I was on the fence abiut a syncro also, but you stated that it still happened while double clutching and match the rev so I discounted the syncro

And went with the next obvious of air in the hydro, but if your shifting okay at the top of the clutch pedal... I doubt its air ither...and id scrap my thought of a worn rubber boot also

Unfortantly... the above is about the extint to what I know about transmissions, its a very weak part of my knowledge about mg...and even that im sure is flawed

I hate to say it, but I fear its engine out, its not going to fix its self

Prop
Prop and the Blackhole Midget

When mine went there was no way of doing 4th to 3rd changes. Double de-clutching, matching road/engine revs or even trying very slowly only got the grating noise and no 3rd gear.

I wish I had kept the broken bits to photograph. It cost me £160 to have it fixed. All the bearings had to be replaced due to fine metal particles from the damaged synchro.

Oh well, I was warned that pushing 90+ BHP through a 1098 gearbox was not on. Although it was fine till I tried to show a clean pair of heels to an Audi that was right up my exhaust pipe.

Rob
Rob aka MG Moneypit

Oh well, I was warned that pushing 90+ BHP through a 1098 gearbox was not on....

is this the reason it failed

hahaha

http://db.tt/2OKJ8DTE

Prop
Prop and the Blackhole Midget

Engine oil is specified for the Morris/MG crash box and if I recall, the syncros in those we're not bronze but ferrous based. The Triumph box uses the standard bronze rings and, except for the worn reverse gear, shifted beautifully using 75W90 synthetic. The box probably should have been left alone when the clutch was replaced. The problem did not present itself in the initial test drive but became dreadfully evident after a few miles of driving. My guess is that the ring was a flawed casting and broke or cracked. Damage during assembly seems unlikely. Odd that it will take an up shift from 2nd although it is starting to grind under that condition also.

The transmission guy recommended trying engine oil but it seems illogical to me to go lighter. 3 in 1? WD40? Maybe banana peels or half a pound of ground beef would do the trick.
Glenn Mallory

Look at it this way glen,

Snow is just around the corner and that means lost days, you can always watch oprea or pull the engine and trans

I think its wishful dreaming to change trans oils to fix the problem...

now if you had a naked jennie in a bottle....©¿©

Prop
Prop and the Blackhole Midget

Glenn,

From your description of it being OK to start with but becoming problematic after a few miles I would vote for either a failure of the synchro ring or it being oversized in the cone and once bedded in had no further movement available so it failed to perform synchronisation and hence crunch. Either way it'll be a gearbox out and examine job, hopefully you'll be able to find out the cause and maybe get some redress.
David Billington

This thread was discussed between 15/11/2014 and 16/11/2014

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