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Gear selection issues when hot
https://www.ausmini.com/forums/viewtopic.php?f=2&t=101817		 Page 1 of 1
Author:  MINIRO [ Mon Apr 24, 2023 2:50 pm ]
Post subject:  Gear selection issues when hot
4 synchro remote change g/box with new Rover baulk rings - using Penrite 20w60 HPR30 Mineral oil


I have noticed recently that after driving for 20mins+ that i have trouble selecting gears. When the engine is cold or first driven there is zero issue, it selects gears nicely but once hot I struggle to select gears (mostly 2nd & 4th)

I have recently flushed/changed the clutch fluid as i thought it may have had moisture in it. - issue is still there.

It is most noticeable when attempting to change gear while the engine is under load, but if I am paying more attn to the RPM and when i select gears, it is somewhat better..

I'm really hoping not to have to pull the engine again as the engine is only 12months old, the gearbox was pulled apart, cleaned, baulk rings replaced and reassembled by my step father (retired mechanic) but this is starting to make long trips unbearable and extremely frustrating.

Any thoughts or suggestions on what the issue is?

Thanks in advance.
Author:  gtogreen1969 [ Mon Apr 24, 2023 3:05 pm ]
Post subject:  Re: Gear selection issues when hot
Oil might be too thick for a tight box. As it heats up the tolerances get tighter. Thinner oil is best for a new box and thick oil for a worn box
Author:  jpodge [ Mon Apr 24, 2023 3:57 pm ]
Post subject:  Re: Gear selection issues when hot
Have you tried adjusting the clutch up to rule that out as a potential cause?
Author:  i got a mini [ Mon Apr 24, 2023 8:22 pm ]
Post subject:  Re: Gear selection issues when hot
its very odd only thing i could think of is possible crank end float set incorrectly when clutch is pressed when hot does engine die down/stall as the end float is listen wrong in the book
Author:  bharp831 [ Tue Apr 25, 2023 7:23 am ]
Post subject:  Re: Gear selection issues when hot
Make sure the clutch lever components are in good condition. Had similar problem and found clutch lever had a crack in the ball head so as the motor got warm, the crack widened and the geometry of the level changed and thus made gear change clunky. Had the problem for about 6 months slowly getting worse as the crack got bigger. Fitted a new lever arm and adjusted as per manual and it is now perfect.

Bazzz
Author:  simon k [ Tue Apr 25, 2023 12:32 pm ]
Post subject:  Re: Gear selection issues when hot
Since its after a rebuild, and gearbox work, I'm gonna be the one to say it... idler gear clearance... thinner gasket with the same washers = oh dear...
Author:  drmini in aust [ Tue Apr 25, 2023 5:28 pm ]
Post subject:  Re: Gear selection issues when hot
simon k wrote:
Since its after a rebuild, and gearbox work, I'm gonna be the one to say it... idler gear clearance... thinner gasket with the same washers = oh dear...

Having built one once with too little clearance and got this, I agree.
2 thou clearance was not enough. Gap reduces when hot.
Author:  MINIRO [ Tue Apr 25, 2023 8:23 pm ]
Post subject:  Re: Gear selection issues when hot
i got a mini wrote:
its very odd only thing i could think of is possible crank end float set incorrectly when clutch is pressed when hot does engine die down/stall as the end float is listen wrong in the book



Thanks mate, na no issue with the engine wanting to die down or stall when clutch is pressed when hot, just the gear selecting issue.
Author:  MINIRO [ Tue Apr 25, 2023 8:30 pm ]
Post subject:  Re: Gear selection issues when hot
simon k wrote:
Since its after a rebuild, and gearbox work, I'm gonna be the one to say it... idler gear clearance... thinner gasket with the same washers = oh dear...


Thanks Simon,

Unfortunately, I am unaware of how the gearbox ran prior to the rebuild as I had purchased it along with another 1098 that had been sitting around for awhile.


Excuse my daft response, but can you please explain how the idler gear having incorrect gap would cause the gearbox to not want to select gear when hot? I would be grateful for your help in understanding this.
Author:  drmini in aust [ Wed Apr 26, 2023 8:05 am ]
Post subject:  Re: Gear selection issues when hot
As I said above if too little idler clearance the idler gear binds when hot. Then the synchro can't give enough torque to spin the drop gears up to allow gear engagement.

Yes there are different gasket thicknesses most red ones around 33 thou and a blue one is 22 thou I bought recently. Measure old one before fitting new.

I have a heap of good sh thrust washers if you need a thinner one. New ones are expensive now.
Author:  Bill B [ Wed Apr 26, 2023 10:34 am ]
Post subject:  Re: Gear selection issues when hot
Is it the primary gear clearance that is getting tighter when hot?
When changing gears with clutch pedal down, the primary gear isn't able to slow down but is still turning with the crankshaft.
Effectively, the clutch is not able to do its job of separating motor from gearbox.
Author:  drmini in aust [ Wed Apr 26, 2023 1:55 pm ]
Post subject:  Re: Gear selection issues when hot
It's usually the idler gear gets tighter as the alloy gear case expands.
Primary gear doesn't because it's steel and crank is too.
Author:  lomin [ Wed Apr 26, 2023 7:49 pm ]
Post subject:  Re: Gear selection issues when hot
Hi, well if people are leaning towards primary gear or idler gear problems, or primary gear being touched by end of a flywheel gone on too far, then easiest way to get an idea is : Drive it to get it hot when problem happens, remove starter, get someone to depress clutch pedal, get a long shaft screwdriver and push the side edge of the clutch plate, between the flywheel and back plate. You should be able to rotate it reasonably easily. Answer ruled in or out. cheers Lindsay
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