Sometimes won’t go into gear on start up

[Nick Brooks]

Hello,

A friend of mine has a ‘64 TR4 like mine. From time to time he can’t engage gear when he first starts the car. Once the engine is warm it all appears to function like it should. I adjusted the pushrod on the clutch slave cylinder for him, and it has improved since then. It has had new clutch master cylinder and new slave cylinder. The car has a comprehensive rebuild file, but there are no details of the gearbox and whether it has been rebuilt (but it all seems to function correctly) and no details of the clutch assembly fitted.

Does anyone have any ideas why it randomly won’t engage gear on start up?

All ideas greatly appreciated!

Thanks, Nick

[RogerH]

Hi Nick,

what gear oil is it using?  The thicker oils   80/'90 etc can be cause this on some boxes when cold.

30/40/50  tend to cope with cold boxes better.

 

Roger 

[Nick Brooks]

Hi Roger,

Trust you’re well & ready for Xmas! Thanks for your thoughts.
He’s using Penrite 40 transmission oil, which I’d say is right for an overdrive box.

Cheers, Nick

[RogerH]

39 minutes ago, Nick Brooks said:

Hi Roger,

Trust you’re well & ready for Xmas! Thanks for your thoughts.
He’s using Penrite 40 transmission oil, which I’d say is right for an overdrive box.

Cheers, Nick

Hi Nick,

Hmm, that rules out the easy one.

It could still be clutch slave adjustment - worth another try.   Or possibly needing bleeding.  Quite easy - ensure the bleed nipple is upper most

 

Roger

[Nigel C]

is it the correct bore/diameter slave cylinder, I think there were two?? 

[Nick Brooks]

Hi Nigel,

Thanks for replying, I think I met you at the Coleford Festival of Transport.

Good point, I think you are right, and I will check with my friend which one is fitted.

Cheers, Nick

[Nigel C]

Hi Nick, You're the guy helping his mate to restore a car?

[Andy Moltu]

16 hours ago, RogerH said:

Hi Nick,

what gear oil is it using?  The thicker oils   80/'90 etc can be cause this on some boxes when cold.

30/40/50  tend to cope with cold boxes better.

 

Roger 

Are we not using different viscosity measuring methods with engine and EP gear oils. 20/50 engine oil having approximately the same viscousity as 80/90 gear. EP90 roughly 50 equivalent.

Back in the day, when the 6 was my only car, first thing on a frosty morning made the engagement of second tight until it had warmed up.

Depending on the oil you choose, an EP 80/90 will give easier cold gear changes than a 90. Those without EP additives may be 20/50, 20/60 or straight 40 could be used. Bear in mind that that multigrade engine oil can be used, the viscosity modifiers used may mean it has short life in a gearbox.

 

[monty]

Always have used Penrite gear 40.

[Rob Salisbury]

Just a thought , is the clutch plate sticking on the flywheel? .... if so engine off, handbrake on, stick it in gear, clutch down and try to start the engine, may go with a bang but this usually works (sticking due to moisture and corrosion and infrequent use).                                                                                                                                                                         Cheers Rob

[Nick Brooks]

7 hours ago, Nigel C said:

Hi Nick, You're the guy helping his mate to restore a car?

Hi Nigel, no that’s not me! His car has been very well restored by the previous owner and has won various awards, including at the TR International I believe.

[Nick Brooks]

22 hours ago, RogerH said:

Hi Nick,

Hmm, that rules out the easy one.

It could still be clutch slave adjustment - worth another try.   Or possibly needing bleeding.  Quite easy - ensure the bleed nipple is upper most

 

Roger

Hi Roger,

Before I adjusted the slave push rod, I did bleed the clutch circuit twice, no air was present. The rod is fitted to the centre hole on the cross shaft lever which I believe is correct. According to the Moss catalogue, we could place it in the top hole for more clutch movement but a heavier clutch. Perhaps I should give that a try?

Cheers, Nick

[RogerH]

Hi Nick,

 shouldn't need to do that.

 

Roger

[Nick Brooks]

On 12/19/2023 at 12:49 PM, Rob Salisbury said:

Just a thought , is the clutch plate sticking on the flywheel? .... if so engine off, handbrake on, stick it in gear, clutch down and try to start the engine, may go with a bang but this usually works (sticking due to moisture and corrosion and infrequent use).                                                                                                                                                                         Cheers Rob

Thanks Rob. I know that technique, but I don’t think it’s that as it only stands in a dry garage for a week or two at a time before being started again.

Cheers, Nick

[Nick Brooks]

Thanks for all your thoughts guys. Does anybody think that it might be a faulty clutch pressure plate with weak springs- could that be possible?

Cheers, Nick

[Ralph Whitaker]

13 hours ago, Nick Brooks said:

Thanks for all your thoughts guys. Does anybody think that it might be a faulty clutch pressure plate with weak springs- could that be possible?

Cheers, Nick

Wouldn`t have thought weak clutch springs would cause it.

My car does not like to go into 2nd when cold, but after about a mile it is OK. I use GB40 oil too. I had a word with Tom Cox about it and he thought it was probably worn thrust washers on the main shaft allowing the gears to move on the shaft when the synchro ring presses on to the gear and the oil is cold and thick, when warmed up and the oil thins then the synchro can do it`s job more easily so it snicks into gear easier, or it could just be worn rings. I have another o/d box on the "round to it" list that I keep promising to overhaul and fit, but can`t face taking the existing box out yet whilst I can live with it.

Ralph

 

Edited December 23, 2023 by Ralph Whitaker
Additional thoughts

[John L]

I used to have this problem on Tractors, in the end we made clutch plates with holes in the rivets to stop the suction that the rivet can cause to the flywheel or the cover,  Can also be caused by some oil on the linings making the plate sticky to the flywheel. Or too much grease on the splines of the clutch plate,  check for the dowel bolts keeping the gearbox to engine in correct alignment.

John

[Nick Brooks]

On 12/23/2023 at 7:14 AM, Ralph Whitaker said:

Wouldn`t have thought weak clutch springs would cause it.

My car does not like to go into 2nd when cold, but after about a mile it is OK. I use GB40 oil too. I had a word with Tom Cox about it and he thought it was probably worn thrust washers on the main shaft allowing the gears to move on the shaft when the synchro ring presses on to the gear and the oil is cold and thick, when warmed up and the oil thins then the synchro can do it`s job more easily so it snicks into gear easier, or it could just be worn rings. I have another o/d box on the "round to it" list that I keep promising to overhaul and fit, but can`t face taking the existing box out yet whilst I can live with it.

Ralph

 

That’s an interesting comment from Pete Cox, one of those things could also be the problem with my friends TR. Thanks Ralph

[Nick Brooks]

On 12/27/2023 at 5:45 PM, John L said:

I used to have this problem on Tractors, in the end we made clutch plates with holes in the rivets to stop the suction that the rivet can cause to the flywheel or the cover,  Can also be caused by some oil on the linings making the plate sticky to the flywheel. Or too much grease on the splines of the clutch plate,  check for the dowel bolts keeping the gearbox to engine in correct alignment.

John

Thanks John, that’s an interesting way around the problem that I’ve never come across before!