Overdrive

[Stagster]

I wasdriving along in second gear andflipped the O/D switch, I was surprised when my O/D worked..!!, in fact it workson all my gears..?

I know it's only meant to work on 3rd and 4th, but my question is - will this damage anything, and should I get it sorted, or leave alone.

(I have only ever used O/D as a 'fifth gear', whilst cruising, and intend to continue using it in this manner)

I had the gearbox re-built a couple of months ago, could this be part of the problem?

Appreciate some comments..., from the guru's..!!

Jer

[Paul B]

imported post

There is a switch on the gearbox which allows the overdrive to be used in only third or fourth gear. I suspect you have a problem with this switch or the associated wiring.

However, be verycareful you must not leave the overdrive engaged while in reverse gear. There is a one way clutch in the overdrive and it will damage it if you reverse while in overdrive.

There is an inhibit switch on the gearbox which should stop this happening.

Regards, Paul,

[DJT]

imported post

Hi Jer,

There should be an inhibitor switch in the circuit so that OD only operates on 3 & 4. This is very similar to the reverse light switch and, depending on the box, can be mounted on the top of the gearlever extension housing, or on a bracket at the base of the gear lever. If the former, then it is virtually impossible to reach without dropping the box.

The attached picture shows the reverse light/ OD inhibitor switch. It also shows three round blanks in the top of the extension housing.One of these could be drilled & tapped to take the switch.Some TRs have two of these switches so that OD will work on 2nd gear as well.

If yours has been by-passed, then be VERY CAREFUL not to engage OD when in reverse as this will break the OD unit.

Dave

[stag8manod]

imported post

Hi Jer,I agree with your two other respondents. When I rebuilt the gearbox on my 1500 Spitfire, also with J type overdrive I made a new internal cam so that it would work on all 4 forward but not reverse. The car has been raced at club and national levels for some 10 years without any OD problems. I don't use 1st OD as it is too close to 1st & 2nd but 2nd OD is used constantly filling the big gap between 2nd and 3rd in the single raill gearbox giving me 4 close-ratios with 2 gear changes. Anyway when it is time to rebuild my Stag box I intend to do the same. Also 2nd OD is also usefull in town saving a number of manual changes.

Regards Ian

[Marco Polo]

imported post

Jer,

It's most likely to be the inhibit switch on the gear box, if you can switch it on and off. however if it engages as you change gear it, in my experience, will be the shuttle valve that is stuck, you can access it by removing the OD solenoid, a change of "O" rings should clear the problem.

I was told by my guru to not use the OD in 1st and 2nd gears as you can overtorque the unit, (it feels like the clutch is slipping), and most important don't use reverse with it engaged unless you want to spend alot of money overhauling the OD unit.

regards,

Raoul