TR4A overdrive issue 2nd gear

[Tiger123]

I drove over to TR70 meet today great to see so many TR gathered together

I noticed a problem with my overdrive today so looking for some direction where to fault find please be gentle as my spannering skills are not great but willing to learn

Ok sat at the lights in 1st gear overdrive not engaged change up into 2nd without engaging overdrive. overdrive kicks in for a moment then drops out shift into 3rd and fourth no problem

Seems to only affect second gear.

Spoke to the overdrive specialists at the show who thought it maybe worth looking at the column mounted switch as the 1st point as it was felt a electrical signal maybe being sent for brief moment?

As ever appreciate your thoughts as owners what maybe the root cause

 

 

Edited August 13, 2023 by Tiger123

[RogerH]

Hi Terry,

when you arrived at the lights where you in OD and then deselect it when stopped

If yes - then the OD may not of come out of OD when sitting there.  Selecting 2nd  then jarr's it out of OD.

Maybe !

Does it happen every time you select 2nd ?

How about deselecting OD when in 4th and then stopping - see what happens.

 

Roger

 

 

[Tiger123]

30 minutes ago, RogerH said:

Hi Terry,

when you arrived at the lights where you in OD and then deselect it when stopped

Not in overdrive

If yes - then the OD may not of come out of OD when sitting there.  Selecting 2nd  then jarr's it out of OD.

Maybe !

Does it happen every time you select 2nd ?

Yes everytime no issues 3rd and 4th

How about deselecting OD when in 4th and then stopping - see what happens.

Haven't tried that one Roger will give it a go hopefully tommorow

 

Roger

 

 

Hi Roger replies above just been out and removed the overdrive stalk checked wiring no visible break in wiring 

[stillp]

Check the terminals on the back of the stalk switch can't short together. I put a piece of fibre insulation over the back of the switch after a short-circuit engaged the o/d in reverse.

A break in the wiring would prevent the o/d from being selected.

Pete

[Tiger123]

Took the stalk apart again gave all contacts a clean with electrical spray cleaner re assembled then road tested it seems to cleared itself   fingers crossed it seems to be OK now

[RogerH]

Hooray

 

Roger

[Tiger123]

It's the small wins Roger that make it worthwhile!

[Andy Moltu]

There are 2 inhibitor switches on a standard TR box fitted with an A type O/D.

One enables the overdrive control circuit (preventing O/D from being engaged by operating the column switch) when in 1st and reverse gears) for 2nd gear and the other works on 3rd and 4th gear. So if you have overdrive problems that are only apparent in in 3rd or 4th but not 2nd or vice versa then it is almost certainly electrical rather than mechanical. 

If the fault is on all 3 then it could be either electrical or mechanical  (switch, relay, solenoid or wiring). If you can hear the solenoid engaging with a clunk and moving the lever then it gets more concerning that there might be an issue with the unit itself.

Glad your fault is sorted.

[Tiger123]

Hi Andy

Thank you for comprehensive reply it would appear it was electrical if my test drive last night indicated next drive out will indicate if its been fixed