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Any Gearbox experts on the forum?
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ukdave2002



Joined: 23 Nov 2007
Posts: 4100
Location: South Cheshire

PostPosted: Sat Aug 10, 2013 6:39 pm    Post subject: Any Gearbox experts on the forum? Reply with quote

This is a duplicate of my MGA post; just before I pull the engine and gearbox out of my newly restored MGA... I'd appreciate experience from the forum members Smile

Since I have had her back on the road the drive has been far better than I was expecting, engine pulls well, transmission nice and quiet, nice neutral handling.......but gear change horrible!..Those who have driven MGA's MGB's, Oxfords, Cambridge's etc will know how precise the gear change should be, my MGA is quite awkward especially between 2nd and 3rd, (both up & down) also selecting reverse, I was hoping it was clutch hydraulics but I don't think that is the case; I have pressure bled the clutch several times + the box is still not easy to change even whilst the engine is not running ... I have mastered the art of getting round these gear change problems; a second application of the clutch normally enables gear selection, when I can't select a gear there is no grating of gears, just a lot of resistance... any advice welcome.

Dave
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kevin2306



Joined: 01 Jul 2013
Posts: 1359
Location: nr Llangollen, north wales

PostPosted: Sat Aug 10, 2013 7:22 pm    Post subject: Reply with quote

Had a similar experience with an old landrover. That was caused by using a transmission oil that was too thick.
Would it be worthwhile doing a fluid service with high quality fluid of the correct spec and seeing if that alters the operation?

Kev
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Uncle Alec



Joined: 14 Jan 2008
Posts: 734
Location: Manchester

PostPosted: Sat Aug 10, 2013 8:40 pm    Post subject: Reply with quote

Now I could well be wrong - and I know I can rely on you lot to tell me if I am - but do I remember these B-series boxes use engine oil, not gearbox oil?
Even if I am wrong, downgrade this post to "check you have the right spec oil".
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kevin2306



Joined: 01 Jul 2013
Posts: 1359
Location: nr Llangollen, north wales

PostPosted: Sat Aug 10, 2013 8:48 pm    Post subject: Reply with quote

http://mgaguru.com/mgtech/gearbox/gt107.htm

Any help?

Kev
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Ray the rocker



Joined: 01 Aug 2008
Posts: 187
Location: south wales

PostPosted: Sat Aug 10, 2013 9:08 pm    Post subject: post subject Reply with quote

Hi dave--I think you`ve stumbled on the problem by default when you can actually engage gears with no difficulty by the operation of the clutch a second time....seems to me that there`s not a complete disengagement of drive from the start.this could point to bad hydraulics or a miss aligned clutch cover pressure plate,try to bleed the clutch in reverse--ie---attatch the bleed tube to the slave cylinder nipple with a clean oil can full of brake fluid, open the nipple,then pump the fluid through until no more bubbles appear in the master cylinder(make sure you surround the master cyl with cloth to soak up any excess fluid!tighten the nipple and test clutch pedal,
it has worked a few times for me in the past....other than that,pressure plate problems relate to perhaps irregular /misaligned fingers on the thrust plate which won`t disengage the drive properly. give it a try ....cheers,
ray the rocker.....
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Farmer John



Joined: 18 Feb 2010
Posts: 181
Location: Manawatu NZ

PostPosted: Sat Aug 10, 2013 10:55 pm    Post subject: Reply with quote

Hello Dave. Is this a problem of non-engagement or faulty selection?
To test selection without gearbox dismantling try this.
Engine not running.
Jiggle, juggle, pump the clutch, rock the car, flick the starter, do whatever is necessary to align the internals so that the lever will slip into a gear smoothly and with a single movement. Begin with second or third. Use only fore and aft lever movement. Once satisfied that it will go into gear nicely move the lever across the "gate" and back, and only across, then retry the gear. Any attempt to engage another gear ( it can happen accidentally) whilst performing this test will render the diagnosis ineffective. Do not worry about the direct drive gear, which I guess will be fourth in your case, but try all the other gears over and over, what you are looking at is an assessment of the overall ability to select any particular gear after the lever has been across the gate in either or both directions. ( Yes, include the reverse plane.)
This procedure takes the clutch and synchros out of the equation.
If you would like to report back with findings we could work through the next step.
How is the gear lever connected to the box, an extension or linkage?
That is a fine job you have done on that car.

John
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PAUL BEAUMONT



Joined: 27 Nov 2007
Posts: 1281
Location: Barnsley S. Yorks

PostPosted: Mon Aug 12, 2013 1:02 pm    Post subject: Reply with quote

About 30 years ago I had a Maxi with the same problem. I had fitted a recon box and had difficulty selecting some gears. The reconditioners recommended the second dip of the clutch for a while until it "ran in". After about 1000 miles the problem went away.
I suggest some miles may fix it!

Paul
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Bitumen Boy



Joined: 26 Jan 2012
Posts: 1733
Location: Above the snow line in old Monmouthshire

PostPosted: Mon Aug 12, 2013 10:59 pm    Post subject: Reply with quote

PAUL BEAUMONT wrote:
About 30 years ago I had a Maxi with the same problem. I had fitted a recon box and had difficulty selecting some gears. The reconditioners recommended the second dip of the clutch for a while until it "ran in". After about 1000 miles the problem went away.
I suggest some miles may fix it!

Paul


That's a point - is the 'box a recon, secondhand or the car's original? I had to fit a recon 'box a few years ago and it could be quite awkward at first, had to double declutch quite often to select gears, but with use it did "run in" and settled down nicely.

I do still think it would be worth nobbling an assistant to bleed the hydraulics again the old fashioned way, I've never had much luck with pressure bleeding gadgets either myself or when I used to use garages - remember picking up one of the Minis I had from a local place after a rear subframe swap, got 1/4 mile down the road, turned round and went straight back because the pedal was spongy - "it's fine, it's been pressure bled..." - but I persisted, and eventually they did it properly, and got a nice firm pedal.
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ukdave2002



Joined: 23 Nov 2007
Posts: 4100
Location: South Cheshire

PostPosted: Sat Aug 17, 2013 8:30 am    Post subject: Reply with quote

Thanks for all the replies, I'm going to work on the car today.

I've just tried the test John advised, and can report it goes back into the same gear ok after moving across the gate.

A couple of other things I didn't mention:

The gearbox was rebuilt by a firm in Chester about 15 years ago, they had to replace loads of components as water had got into the innards and many of the gears had the case hardening damaged, so the box is a mix of old and new components.

Even moving across the gate feels stiff, with or without the engine running.

There is never any grating; just awkward to select the gears.

Cheers

Dave
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ukdave2002



Joined: 23 Nov 2007
Posts: 4100
Location: South Cheshire

PostPosted: Sat Aug 17, 2013 6:02 pm    Post subject: Reply with quote

Progress Very Happy

Today I changed the gearbox oil; although I'm 90% sure it was filled with 20/50 there was a doubt!
The overall change was still stiff, so I decided to look at the remote extension , this can be done from inside the car, I was thinking that after 15 years of standing in may require some lubrication Question I was looking for some where to add some oil so removed the remote damper, this is what I found:





When ever the last time the damper was fitted it ended up being more of a wedge!

I cleaned up the housing and turned a new plunger:



A combination of changing the oil and fixing the remote damper has improved things massively, 2-3 up or down is better but around 30 % of the time needs a second application of the clutch.

Your words of wisdom welcome Very Happy

Thanks for the advice this far

dave
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Kelsham



Joined: 18 Jan 2009
Posts: 349
Location: Llandrindod Wells Powys

PostPosted: Sun Aug 18, 2013 10:04 am    Post subject: Reply with quote

I believe that TR7s changed to Dexron automatic gearbox oil in their five speed boxes to assist gear changing.
Might be worth a try.
Regards Kels
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Farmer John



Joined: 18 Feb 2010
Posts: 181
Location: Manawatu NZ

PostPosted: Sun Aug 18, 2013 12:59 pm    Post subject: Reply with quote

Hi Dave, excellent work finding and sorting the wicked work on the plunger. You are doing the right thing by making sure the oil is correct. There is nothing more to be discovered without dismantling now. If you were to make a major change to oil viscosity as Kels suggested, and it is well worth a try, there might be enough improvement to confirm that the problem is in the synchros.
A complete cure will require new parts, there is way too much work involved to be trying used parts, which means you can do the job yourself. There is no magic involved, proper tools cleanliness and care are all that are required.

John
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peter scott



Joined: 18 Dec 2007
Posts: 7113
Location: Edinburgh

PostPosted: Sun Aug 18, 2013 10:31 pm    Post subject: Reply with quote

Farmer John wrote:

A complete cure will require new parts, there is way too much work involved to be trying used parts, which means you can do the job yourself.
John


You might need to buy new synchro springs but the cones can be ground in just like grinding in valves. (Same paste.)

http://www.nostalgiatech.co.uk/new_page_1.htm

Peter
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1939 SS Jaguar 2 1/2 litre saloon
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