Difficulty selecting gears when hot

[ncurtis1]

Hi I just joined the Forum yesterday and would appreciate any comments about my current problem.

I have a 1964 Minor 1000 that has still to do 40,000. However, it has been running a rebuilt 1275 Marina A plus engine for some years without any problems. I am now running a rebuilt 3.9 diff (fitted last year) and earlier this year added a rebuilt 1275 Midget gearbox fitted with a roller bearing thrust to complete the job.

The issue I have is that everything runs fine until I believe things get hot and I am unable to get in or out of gear/change gear without extreme effort. If I turn off I can select gears but it feels like the clutch is not disengaging properly. The problem is intermittent as I can drive 15 miles without problem one day and the next cant change gear after a 5 minute drive to the shops. It is driving me nuts as a lot of money has been spent to effectively retrograde! I am almost thinking of going back to the original gearbox which gave me no trouble, or the alternative reverting to carbon thrust. Either way it is a costly gearbox out job.

I have been viewing comments and advice on the Forum which has encouraged me to seek advice and confirm my gut feelings.

Any advice would be greatly appreciated

Thanks for reading

[philthehill]

Welcome aboard the forum.
Firstly I would check that the clutch clearance is correct.
What clutch assy have you got fitted and is the release mechanism mechanical or hydraulic?
Reciept of the above information will help determine the next tranche of advice.

[ncurtis1]

Good morning and thanks for your prompt reply.

The clutch assembly is Modified Borg and Beck. Modified in that the gearbox builder advised removal of the pressure pad so that the roller bearing acts directly on the fingers to give the right clearances. I'm not sure how to measure the clearance. The activation is hydraulic and worked perfectly fine on the 1098 box.

[philthehill]

Thanks for the reply and additional information.
I have the same type of modification to the clutch pressure plate on my Minor so I have an understanding of what has been removed i.e. rubbing plate.
Regarding checking the clearance with the hydraulic actuation system - all you can do is make sure that there is some free play at the slave cylinder push rod. My own system is hydraulic and I have a adjustable slave cylinder push rod to allow for any variations in operation.

Hydraulic clutch 1.JPG (831.58 KiB) Viewed 361 times

Hydraulic clutch 3.JPG (855.79 KiB) Viewed 361 times

Make sure that you have free play at the master cylinder push rod.
I suspect that you do not have sufficient clearance at either the slave cylinder or master cylinder or both.
At the master cylinder the pedal should be able to be pushed down at least 3/4" before operating the master cylinder. At the slave cylinder you should just be able to rattle the push rod.
If the 1275cc clutch release lever was not fitted then the clutch operation would be compromised.
See details in the attached link below:-

http://gerardsgarage.com/Garage/Tech/TO ... arings.htm

[ncurtis1]

Thanks I appreciate your reply. Looks like you have a roller bearing or you would not have also removed the pressure pad, If so do you have any problems? I will check the items you mentioned when I can get under the car(a few lower back chassis problems of my own at the moment).

Have you seen this by any chance?
https://www.youtube.com/watch?v=4KIdkOWVcGg
makes you think.

Will check the items you mentioned asap and post result.

[philthehill]

Regarding the 'You Tube' video - I am aware of the concentricity problem and have had to get around the problem with the majority of clutch assys fitted to my Minor which have always been non standard ever since I fitted the 998cc race engine way back and various uprated gearboxes.
I do have a roller bearing set up which was produced by CS Autoclassic's in the early 90s.
The current gearbox is a Quaife/Ford item with the nose which carries the roller bearing carrier but I have faced the concentricity problems with the MG 1275cc gearbox previously fitted.
The roller release bearing with the Quaife/Ford gearbox therefore remains concentric to the rotating clutch. The out of concentricity is then transferred to the release arm pivot. Whilst I am able to get away with not modifying the release arm one of the ways of getting around the out of concentric motion is to slot the release arm pivot so as to allow the release bearing to find its own concentric path.
I have never had any problems with the roller release bearing and that operates a Ford RS 2000 7.5" full race clutch which needs a very heavy push to operate. I have fitted a small internal diameter master cylinder to increase the mechanical advantage.
See the Peter May Engineering web site regarding the release arm concentricity:-
https://www.petermayengineering.com/pro ... aring-kit/
See also the Front Line Developments web site:-
https://s3.amazonaws.com/frontline-deve ... -speed.pdf

[ncurtis1]

Finally got to lift and get under the car only to discover that a 1098 clutch fork has been fitted by the garage to a Midget 1275 gearbox. Opens a whole new can of worms!

Roller release bearing ,1275 gearbox, Morris Minor clutch fork, an ensemble to make you scratch your head!

probably first course need to have a quiet shout at the "specialist garage" no names no pack drill.

Mmmmmmm

[philthehill]

I am glad that you got to the bottom of the problem.
Just fit a 1275cc release arm and all should be well.
https://www.ebay.co.uk/itm/385024269687 ... SwRTVizJ06