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gearbox
Posted: Mon Apr 30, 2012 5:44 pm
by kennatt
just lost top gear after giving the splitty a blast out, will not select top properly sometimes goes in and stays others(Mostly) throws the gear out.You can feel that it's not engaging,think best solution would be a secondhand box rather than a strip down probably selector forks worn or syncro. so in market for a 948 box if anyone has a known decent one.Then I may rebuild mine at my leisure,strange that There was no previous warnings,just suddenly threw the gear after a quick change up.Distance no object can arrange my own carrier but would prefer north east england if possible. Cheers
Re: gearbox
Posted: Mon Apr 30, 2012 6:28 pm
by bmcecosse
Yet it works normally in all other gears ? I would check the lever mechanism for any looseness/free play. 4th gear is a direct drive, so usually pretty much troublefree. But it could be bearing [problems. As you suggest - another box will be the best way forward in the short term.
Re: gearbox
Posted: Tue May 01, 2012 7:07 am
by kennatt
yes all others are ok when it actually goes into top even from 60mph if you take your foot off it stays in gear with no sign of jumping out. but most times it will go sort of just in then when I let clutch out slips straight out,can be held in with a bit of force as you say unusual for this sort of fault in top, mainly lower gears, can't quite work out why. Might take the cover off and have a look .Just dosen't feel as though it is actually meshing into the gear
Re: gearbox
Posted: Tue May 01, 2012 9:09 am
by bmcecosse
Check all the lever/extension mech in case something has come loose and is blocking the movement - maybe even just the top 3 bolts allowing the lever to come loose?
Re: gearbox
Posted: Tue May 01, 2012 11:52 am
by kennatt
already tried the three bolts,I think it may be the selector fork rod bolt since It happened the first time then second try engaged and ran fine for the next 10 mile changing ok then it started again and eventually will not engage properly.going to drop the box and have a look
Re: gearbox
Posted: Tue May 01, 2012 2:37 pm
by bmcecosse
Well you can get at the fork through the side plate - so just drain and remove the plate as a first check.
Re: gearbox
Posted: Wed May 02, 2012 7:28 am
by kennatt
did that last night and can't see anything loose so looks like a box swap,shame because it was a very quiet and dry box no crunching even on rapid gears changes
Re: gearbox
Posted: Wed May 02, 2012 9:03 am
by MarkyB
If you can get the floor out it would be worth removing the remote from the top of the box, the lever that goes into the box can get loose on the shaft.
Re: gearbox
Posted: Thu May 03, 2012 7:21 am
by kennatt
did that and put into top straight from gear box still jumps out,checked all springs and plungers all ok grove in selector rod dosn't look worn,everybody I have spoken to including a guy That has had lots of dealings with these boxes(Miget rebuilder) and a guy at easygears rebuilders they all say ..........neverheard of this sort of problem yes well worn ones will throw top gear out on the overrun,but once drive is taken the gears tend to drive into each other an hold. Looks like another box and then I'm going to strip the old one to see if I can see what has caused it,Could do with the practice about 20 years since I had a box in bits (Sad eh,nothing else to do need another rebuild project maybe)
Re: gearbox
Posted: Thu May 03, 2012 9:10 am
by bmcecosse
I agree - most unusual problem.
Re: gearbox
Posted: Fri May 04, 2012 8:00 am
by kennatt
well found it I think

decided to take box out and fit another that I have managed to find.Once out it was clear that the first motion shaft bearing had broken up, the first motion shaft was flopping about and you could see the bearing in the casing moving in its housing, This wasn't seen with the box in situ because the clutch and spiggot bush in the engine were holding the end of the first motion shaft and preventing any movement by hand but obviously on drive it was thrashing about and so must have been causing a missalignment of fourth gear,it wouldn't effect third because the gear is at the rear of the box so less movement on the shaft.Strange that there was absolutly no noise from the box,and mental note to check the state of the spiggot bush (Could be that, worn or missing, and that has caused the bearing to fail in the first place) This has to be the fault cos I can't see anything else wrong inside .Dont know if its worth trying to rebuild it, From memory I think you need a full stripdown to replace that bearing because it is driven in from inside the box .have to get the books out.Now that I'm at this stage going to take engine out to clean up the engine bay and put a new friction plate into the clutch and much easier to mate the engine and box out of the car to refit.
Re: gearbox
Posted: Fri May 04, 2012 9:44 am
by bmcecosse
I was going to suggest bearing failure - but you hadn't mentioned any strange noises. I think it will be well worth rebuilding if it was otherwise working ok. Put a new syncro ring in 2nd gear - and check the layshaft/bearings while in there!
Re: gearbox
Posted: Fri May 04, 2012 6:05 pm
by MarkyB
Is there a spigot bearing in the middle of the flywheel?
The lack of one would put extra strain on the bearing.
Re: gearbox
Posted: Fri May 04, 2012 7:41 pm
by kennatt
Re: gearbox
Posted: Fri May 04, 2012 8:35 pm
by linearaudio
Its your money!! If the box is already out and all other gears were fine, I would be tempted to put a new front bearing in, and as a matter of course, replace the needle bearing between 1st and 3rd shaft. The box is easy to strip, but needs a certain simple approach regarding drifting 1st and 3rd shafts with their bearings out with a suitable screwdriver/ hammer mx

. There does exist a very helpful WSM download somewhere... BMCEcosse may just be able to locate the relevant link

.
Don't be put off by any implied technology of the moggy box- I have 3 which I am juggling with at the moment- hardest bit seems to be registering the tail section with the main box on re-assembly, but hardly mind boggling stuff!!
Re: gearbox
Posted: Fri May 04, 2012 9:01 pm
by bmcecosse
£100 for a 948 box?? A bit over the top!! Yes the 1098 box is obviously better - but the 948 box is fine for a 948 engined car. Some of the bits are hard to get now - but bearings are easy.
Re: gearbox
Posted: Sat May 05, 2012 8:17 am
by kennatt
Re: gearbox
Posted: Sat May 05, 2012 9:49 am
by bmcecosse
Let's see some Scimitar pics!!
Re: gearbox
Posted: Sat May 05, 2012 8:29 pm
by lambrettalad
Hi
not having driven a moggie with an old style gear box ,I found it useful to remember it has three moving gears 2nd 3rd and 4th and two stationary gears 1st and reverse,also the gates are more like a X rather than a H
I remember cupping my hand whist changing gear ,still do it today,having re-educated my left foot, brain and hand

Re: gearbox
Posted: Mon May 07, 2012 9:29 am
by kennatt
Yes will put some photos on as soon as I get my camera back from my daughter who borrowed it for a couple of hours three weeks ago