Conquest preselector gearbox adjustment

migray
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Joined: Fri Feb 26, 2016 10:31 pm
Location: Bakewell

Conquest preselector gearbox adjustment

Post by migray » Sat Aug 12, 2017 11:31 pm

I am having problems when selecting reverse on my Conquest NDHC. After releasing the gear change pedal the gearbox shakes and makes snatching noises. The car will drive backwards but I have had problems getting enough traction to reverse up a slope.
I have tried to adjust the gearbox (having made sure the selector rods and joints are all okay).
The manual suggests turning the adjuster screw for the gear band clockwise by a half turn if the gear is slipping, and then turning the pull rod nut back one turn before repeatedly operating the gear change pedal until the nut stops turning. It suggests turning the adjuster screw anticlockwise if the take up is fierce.
I am not sure if I have slipping or fierce take up though.
I have tried adjusting the screw both ways but so far I cannot get smooth take up in reverse gear - if I hold the car on the brake and rev the engine it makes an awful noise and the gearbox case tries to turn.
Does anyone know if there is a procedure to set the initial position of the adjuster for the reverse gear band - I am not sure if it needs to be screwed in or out? Or can someone advise what the issue may be?
I can see the gears selecting without problem when I operate the gear change pedal with the engine not running. Unfortunately you have to keep the cover on top of the gearbox when the engine is going as oil is pumped out otherwise.

Advice appreciated.

Mike

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theoldman
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Location: Bacton on Sea, Norfolk UK

Re: Conquest preselector gearbox adjustment

Post by theoldman » Sun Aug 13, 2017 8:03 pm

I would hazard the linings on the reverse gear brake bands are worn out.......................
Normal for Norfolk

migray
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Joined: Fri Feb 26, 2016 10:31 pm
Location: Bakewell

Re: Conquest preselector gearbox adjustment

Post by migray » Wed Aug 23, 2017 6:12 pm

Well I have stripped the gearbox down and the brake linings seem to have very little wear on them. The gear clusters all seem fine and the actuating rods etc look straight without any obvious wear. I am rather puzzled. The gearbox would select reverse but wouldn't transmit much torque without trying to shake the gearbox and making metallic noises. There is a part of the case, a stiffener web just above the ball bearing race, which is a little shiny, perhaps it was rubbing?

Mike

migray
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Joined: Fri Feb 26, 2016 10:31 pm
Location: Bakewell

Re: Conquest preselector gearbox adjustment

Post by migray » Thu Aug 24, 2017 4:24 pm

busbarrod.jpg
Still trying to find what is wrong. Found that the bus bar operating rod shows signs of wear, with a sharp edge to the top of the slotted section. Also at the point where it is riveted to the busbar, one of the rivets seems to have moved and the plate holding the rod in is raised.

The other sign of wear is the hook on the reverse brake band. The hooks on each side do not seem perfectly aligned and are not as deep as the hooks on the other bands. The operating rod hooks seem unmarked however. I attach a couple of photos to help illustrate what I am saying.

I am not sure how significant either of these items are for explaining the symptoms I was experiencing. Does anyone have more in depth knowledge please?

Mike
Attachments
reverseband_LI.jpg

Stan Thomas
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Location: Penkridge. Staffs.

Re: Conquest preselector gearbox adjustment

Post by Stan Thomas » Fri Aug 25, 2017 5:04 pm

Check if the large rubber (metalastik) mounting on the back of the gearbox has not gone soggy - and check the rubber cones on the torque reaction buffers are O.K. and providing a light clamping action. Both these will cause shuddering etc. if not correct.

migray
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Joined: Fri Feb 26, 2016 10:31 pm
Location: Bakewell

Re: Conquest preselector gearbox adjustment

Post by migray » Mon Sep 04, 2017 10:24 pm

I have been trying to reassemble the gearbox. The friction bands all looked as if they had minimal wear. I was trying to follow the instructions on setting the bus bar height. My diagnosis of why I was having trouble with reverse was that the bus bar was coming up too high and I think it had been misadjusted in the past.
The manual has little information it seems. I selected reverse and measured the height of the bus bar. Unselected it and adjusted the automatic adjuster nut by hand, then selected it again until the height was close to that in page 24 of the gearbox section of the Conquest manual (5.53"). I then adjusted the adjusting screw on the band so it was almost touching the adjuster table when it was selected. As best as I can determine from the information in the manual this should set the initial position of the adjuster.
However when trying to select 3rd gear there was a crack and the band broke! The selection was quite fierce but I'm not sure why it should have enough force to break the band. I now have to dismantle the gearbox again and find the best spare gear brake band to replace it. As far as I can see 3rd, 2nd and 1st bands are identical, though the adjuster nuts for 2nd and 3rd are the same while 1st and reverse are the same.

Any advice from someone who has more insight or information would be appreciated.

Mike

qantasqf1
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Joined: Mon Mar 07, 2016 10:13 pm

Re: Conquest preselector gearbox adjustment

Post by qantasqf1 » Tue Sep 05, 2017 8:47 am

Mike, when you said the band broke, do you mean the steel band itself, or the lining that's riveted to it? If the former I've never heard of this happening and it must have been cracked in the first place. Anyway, as far as band adjustment is concerned, I built a DB18 gearbox from 3 spare boxes and this is what I did after installing the gearbox in the car. I backed off the stop bolts of each gear to get the bloody things out of the way and screwed up the pull rod adjustment nuts, gear at a time, until there was no toggle action at all when operating the engagement pedal. Then I unscrewed the pull rod nut on the gear I was working on until toggle action just took place, then unscrewed it further until a gap of about 1/2 inch between the table and the band's stop bolt was obtained. Same procedure for all the gears. Since this is only a provisional setting what I did next was to test drive the car. I found the shifts were slightly fierce, so I screwed the pull rod nuts clockwise in each case 1/4 turn at a time (the bands are very sensitive to adjustment) and a softer shift was the result...except reverse which slipped slightly before fully gripping so I unscrewed the pull nut i.e., increased toggle action by about 1/8 of an inch if memory serves and that fixed it. Finally I set the stop bolts so they were just contacting the adjuster. In short, I did it by trial and error. That was over 4 years ago and the gearbox is fine.
Steve

migray
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Joined: Fri Feb 26, 2016 10:31 pm
Location: Bakewell

Re: Conquest preselector gearbox adjustment

Post by migray » Tue Sep 05, 2017 6:39 pm

Thanks for your information. I am conscious there is discussion on this forum about experts and those who know what they are doing, but some of us have to learn somehow! And we need to pool what experience we can.
The metal band did break, not sure how but I attach a picture. The gearbox I am using for spare parts has various worn edges and loose brake linings but I have managed to assemble a good brake band to use for 3rd.
Just finished tightening up all those screws again!

Mike
Attachments
3rdgear.jpg

qantasqf1
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Joined: Mon Mar 07, 2016 10:13 pm

Re: Conquest preselector gearbox adjustment

Post by qantasqf1 » Tue Sep 05, 2017 9:01 pm

I forgot to mention the fact that the annuli are grooved to increase grip. The pitches of the grooves are different for individual gears so it's not a good idea to fit a used brake band that wasn't originally for that particular gear.

migray
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Joined: Fri Feb 26, 2016 10:31 pm
Location: Bakewell

Re: Conquest preselector gearbox adjustment

Post by migray » Tue Sep 05, 2017 10:56 pm

You are quite correct the grooves in the gear brake drums are at differing pitches. I think 1st and reverse are the same, and 2nd and 3rd the same. However the parts manual shows the friction linings as being the same for each gear. Does this mean they take up the shape of the drum grooves once fitted? I remember reading about someone fitting new brake bands and having lots of grabbing before they bed in, is this why? I am interested because I have fitted a first gear bandin the position of a 3rd gear band as it was in better condition. The loose inner band is from the original 3rd gear, so will fit, but the outer band which is riveted to the brake band itself has the wrong pitch to fit the drum.

Still much to learn.

Mike

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