16 replies to this topic

[Dave K]

I have eventually completed doing a total restoration on my sons 1987 Mini. I bought a 1275 engine and gearbox complete off ebay last year. I overhauled the engine completely but foolishly didn't get the gearbox checked and now it jumps out of gear in 2nd and 4th.

 

Anyone had this problem and what is the solution? 

 

I still have the 998 engine and gearbox on a pallet wrapped in industrial clingfilm so I am thinking of doing a swap with that gearbox. I know it fits but I would still like to sort this box out so I can swap it for the mental 1275 mini gearbox that crunches in second my youngest son has.

 

Any suggestions would be helpful.

 

Dave

[BSAjohnnyboy]

I had a similar problem with my newly built1275 engine  & gearbox. I found that the rubber gaitor for the rod change seal was compressing when selecting 2nd & 4th gear then pushing it back out of gear. Hope this helps.

 

 

[Spider]

As it sounds like it's jumped out a few times now, there's a very good chance that it's beyond anything repairable externally. After they jump out of gear a few times, especially under power, the dogs on the gears themselves round off and they will never hold gear.

 

It could have been caused by a number of things, but given your description, I'd guess here that the Main Shaft Bearing is really badly worn, allowing the main Shaft to walk back and forth from Power On to Power Off, and in doing so, pulling the geartrain out of those gears from the side thrust of the gears themselves.

 

If you are to fit your 998 gearbox, at the very least, have it looked at before doing so, regardless of what ever condition you think it might be in. Guessworks seems to be the guy to see for this stuff.

[Dave K]

Some good points, everything is either new or recon on this car no expense spared except for the gearbox! I did fit a new gaiter on the rod change gaiter so worth checking that first. This isn't the first car I've restored and the quality of rubber parts like many other parts are dubious.

 

I did fit an auto selector from minisport and a quick change gearlever but removed them both just to see if they affected anything, by fitting the original gear lever all I achieved was to fit a gearlever that slops around all over the place.

 

I did forget to mention that while you are giving the car some gas it will stay in gear, as soon as the gas is off it drops out which I think is what you are saying Moke spider. I would have thought that if the main shaft bearings had gone then there would be some sort of noise from the box which is very quiet, however I know there are lister's here who know more about Minis than I'll ever know.

 

The 998 gearbox was fine before I removed it, not dropping out of gear or crunching in any gear. The engine was knackered and was the original unrestored engine having done 75K miles from new.

 

Dave

[Guess-Works.com]

If it drops out of gear on run down... 9 out of 10 times it's because of worn selector forks... causes of this are many but most of the time it's someone holding it in gear, while driving along... wearing away at the thrust side of the fork and eventually they are not able to fully engage the gear and it drops out when not under load...

 

You'll probably find the 998 gearbox is 10 times better condition wise, however, once bitten, twice shy ?

[Dave K]

How difficult is it to change the selector forks? I'm a mechanical engineer with plenty of access to tools.

 

Dave

[Guess-Works.com]

Complete strip of gearbox

[Dave K]

Ah, either exchange box or the 998 one.

 

Thanks.

 

Dave

[Ethel]

Sounds like you could have the makings of 2 good gearboxes anyway. Worth checking the engine can't rock far enough to pull it out of gear, probably not that likely but much easier to fix.

[idlethumbs]

Mine used to pop out of 2nd. I fitted a gear bias to the rods so the stick centralises. I did it for different reasons than it popping out but it hasn't popped out since in over 12 months gears feel tighter. Maybe worth a go. They are about £20 from minispares.

[Dave K]

Is a gear bias a spring loaded gadget with two forks on it, fits on the change rod and the prongs go either side of the shaft above? If so I have one of those.

 

Dave

[Spider]

I don't like to rain on anyone's parade and I like to read other's ideas and approaches, as I've said before here, I'm only learning like the next guy.

 

However in regards to fitting anything to the shifter to 'fix' problems like these, I just feel that while it may appear as a fix, I think it's only masking an underlying problem and delaying the inevitable.

 

Whether it be Bearings or Selector Forks or what ever, I really think the box needs to come out and be stripped down, checking everything. I've found once something (jumping out of gear, noise that wasn't there, grinding in to gear etc) upon stripping the box, and checking them, it's evident that the whole box was up for an over haul, then it's all good to go again for another 100 000.

 

Sometimes masking underlying issues while delaying the inevitable, only makes them worse and much more expensive to repair.

[idlethumbs]

Hi Dave k. Yes that's the one.
I agree that potentially it may mask the problem although mine had just started and it's been fine since as well as the bias being a great thing to improve the drive.

[mina08]

I had the same problem, but it was only jumping out of 2nd when coasting, after an engine/gearbox rebuild. So i fitted the MS gear Bias and it stopped, so it could be something in the selector box under the gear stick.

[Steve220]

I asked John at guessworks about this when dropping off my gearbox. He said to look at replacing the shifter bobbins.