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1986 Fuso bus air assist gearbox issues
2 months 1 week ago #253220
by Grae
1986 Fuso bus air assist gearbox issues was created by Grae
Hello everyone I have a friend with a 1986 Mitsubishi Fuso Motorhome and he is having issues with his gear changes. It has the air assist 5 speed manual.
The first issue he has was it was grinding going into 4th. He removed the box and sent it to a repairer and they found no problems with it mechanically.
He put the box back in and now is getting weird things happening.
When the bus is stationary he can select every gear without issue, all the correct lights come on when engaging every gear and the bus will move fine.
But as soon as he starts to move and engage second gear it will not select and the light goes out. If he comes to a stop he can easily select any gear again and the lights work. Reverse works as well.
He has tested all the solenoids on the bench and the air tank has pressure. The regulator on the tank is working.
If he leaves the bus over night the air tank is empty so a small leak sounds likely somewhere.
Can anyone shed some light on this weird issue please?
Thanks Grae.
The first issue he has was it was grinding going into 4th. He removed the box and sent it to a repairer and they found no problems with it mechanically.
He put the box back in and now is getting weird things happening.
When the bus is stationary he can select every gear without issue, all the correct lights come on when engaging every gear and the bus will move fine.
But as soon as he starts to move and engage second gear it will not select and the light goes out. If he comes to a stop he can easily select any gear again and the lights work. Reverse works as well.
He has tested all the solenoids on the bench and the air tank has pressure. The regulator on the tank is working.
If he leaves the bus over night the air tank is empty so a small leak sounds likely somewhere.
Can anyone shed some light on this weird issue please?
Thanks Grae.
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2 months 1 week ago #253223
by grumpy gumpy
Replied by grumpy gumpy on topic 1986 Fuso bus air assist gearbox issues
I don’t know if it’s the same style system but we had issues with the air brakes leaking slightly which caused the air assist clutch not to work, was fine to drive as long as you didn’t use the clutch and the brakes at the same time
Gumpy
Gumpy
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2 months 1 week ago #253227
by cobbadog
Cheers Cobba & Cobbarette
Coopernook, The Centre of our Universe
Working on more play time.
Replied by cobbadog on topic 1986 Fuso bus air assist gearbox issues
Out with the soapy water
Cheers Cobba & Cobbarette
Coopernook, The Centre of our Universe
Working on more play time.
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2 months 1 week ago #253228
by 180wannabe
Replied by 180wannabe on topic 1986 Fuso bus air assist gearbox issues
Is there an inline filter before the regulator?
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2 months 1 week ago - 2 months 1 week ago #253236
by jon_d
Replied by jon_d on topic 1986 Fuso bus air assist gearbox issues
Not sure if this will help or not.
I have a 6 speed isuzu box with air assist (both lever and clutch) of that era in the bus.
1. The wrong oil gave me all sorts of problems. GL4 is very different to GL5. Mine uses GL4. GL5 makes the synros sticky and the brass wears out pretty fast.
2. The cables need to be adjusted incredibly accurately. The gear lever in 'rest' has align with the 3/4 gate perfectly. If it doesn't, the gear lever spring (and feel) AND the gate detents are not aligned when finding 5/6 and 1/2. Goodness knows how many time I crunched gears until I worked that out.
I have a 6 speed isuzu box with air assist (both lever and clutch) of that era in the bus.
1. The wrong oil gave me all sorts of problems. GL4 is very different to GL5. Mine uses GL4. GL5 makes the synros sticky and the brass wears out pretty fast.
2. The cables need to be adjusted incredibly accurately. The gear lever in 'rest' has align with the 3/4 gate perfectly. If it doesn't, the gear lever spring (and feel) AND the gate detents are not aligned when finding 5/6 and 1/2. Goodness knows how many time I crunched gears until I worked that out.
Last edit: 2 months 1 week ago by jon_d.
The following user(s) said Thank You: 180wannabe, cobbadog
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1 month 3 weeks ago #253487
by Grae
Replied by Grae on topic 1986 Fuso bus air assist gearbox issues
Thanks for the replies. Does anyone know what the regulated pressure is set at from the factory for the transmission?
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1 month 3 weeks ago #253488
by jon_d
Do you mean the air assist on for the cable selector/quadrant box (?) or the air assist for the clutch(?) or something else?
Replied by jon_d on topic 1986 Fuso bus air assist gearbox issues
What do you mean by "the transmission"does anyone know what the regulated pressure is set at from the factory for the transmission?
Do you mean the air assist on for the cable selector/quadrant box (?) or the air assist for the clutch(?) or something else?
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1 month 3 weeks ago #253489
by Grae
Replied by Grae on topic 1986 Fuso bus air assist gearbox issues
Both actually.
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1 month 3 weeks ago #253492
by jon_d
Replied by jon_d on topic 1986 Fuso bus air assist gearbox issues
A friend has a Fuso import bus (motorhome) of that era. He reckons both tanks are coupled pressure wise (brakes and service).
He measured 110psi on the first tank.
hope this helps.
He measured 110psi on the first tank.
hope this helps.
The following user(s) said Thank You: PaulFH
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