getting overdrive back on

[cleverusername]

I have the gearbox on, but I put the overdrive on upside down. No problem, just slide it off the shaft, rotate, put it back. Nope, It won't go back on. I have even taken it off to realign the splines (can be done if you remove the middle section of the exhaust and the engine is a few inches forward), still no luck. It gets stuck just when the studs engage. The splines must be out of line, but they look like they are lined up. Any suggestions how to get out of this mess?

[Jon Tilson]

Make sure the mainshaft oil pump drive cam is upper most so it clears the pump. Make sure the one way roller clutch splines are aligned.

They should be if it went on before. I didnt realise it was possible to put it on upside down. No wonder your were 2 holes short on the rear mounting.

Jonners

[Henk]

You might have a spare mainshaft lying around? If so, use it to re-align the splines (when od is placed on workbench probably easier to do than when standing under car).

[Richard the old one]

I have been there a number of times. You were just lucky the first time just keep trying it will just slide on when the splines are aligned correctly.

You have found out why people were telling you not to take the gearbox and O/D apart.

There must be a secret to doing it but I do not know it. Lets hope someone can help.

[Jon Tilson]

Nobody has a spare o/d mainshaft unless they are rebuilding more than one box at a time...

It wasnt his fault Richard. He bought the box and o/d from 2 different sources. They didnt come together. I'm still struggling to see how he fitted it
wrong way up though.

Jonners

[cleverusername]

I have been there a number of times. You were just lucky the first time just keep trying it will just slide on when the splines are aligned correctly.

You have found out why people were telling you not to take the gearbox and O/D apart.

There must be a secret to doing it but I do not know it. Lets hope someone can help.

In my defence the od and gearbox have never been properly together. Alas I assumed it would only fit on one way and didn't look at the diagram carefully enough.

Hopefully the splines are still out of line and adjusting them with a screw driver will fix the problem. It is very dumb design, all that complexity and weight, when the same job could be done with an of gear in the box.

[RodR]

Reading this I remembered I have a booklet of Triumph Service Training Notes on this Overdrive. I can't seem to attach a scan so I have copied a relevant section:

"Refitting to Gearbox

Using a screwdriver of suitable length rotate the inner member of the uni-directional clutch in an anti-clockwise direction until the splines of this member are in line with the splines in the planet carrier.

Ensure that the pump cam and planet carrier retaining clip are correctly located on the main-shaft. Next engage bottom gear and after fitting a new joint to the front face of the overdrive offer the unit up to the gearbox. Rotate the output shaft of the unit in a clockwise direction at the same time applying slight forward pressure until the splines become engaged.

Ensure that the pump strap assembly rides smoothly onto the cam and that the overdrive pushes home to the adaptor plate face without excessive force. Next fit and tighten the eight nuts which secure the unit.

If the overdrive fails to meet the adaptor plate face by approximately 5/8” it means that the planet carrier and uni-directional clutch have become mis-aligned. In this case remove the unit and re-align the splines."

[zombeh]

It is very dumb design, all that complexity and weight, when the same job could be done with an of gear in the box.

I think that greatly depends on what the job you want it to do actually is and how you'd go about getting another gear in the box.

A sprint overdrive box weighs the same as a 5 speed rover box.
It's got another gear (the really useful one) or even two if you want.
You need to take your foot off to change gear with a 5 speed.

[cleverusername]

Reading this I remembered I have a booklet of Triumph Service Training Notes on this Overdrive. I can't seem to attach a scan so I have copied a relevant section:

"Refitting to Gearbox

Using a screwdriver of suitable length rotate the inner member of the uni-directional clutch in an anti-clockwise direction until the splines of this member are in line with the splines in the planet carrier.

Ensure that the pump cam and planet carrier retaining clip are correctly located on the main-shaft. Next engage bottom gear and after fitting a new joint to the front face of the overdrive offer the unit up to the gearbox. Rotate the output shaft of the unit in a clockwise direction at the same time applying slight forward pressure until the splines become engaged.

Ensure that the pump strap assembly rides smoothly onto the cam and that the overdrive pushes home to the adaptor plate face without excessive force. Next fit and tighten the eight nuts which secure the unit.

If the overdrive fails to meet the adaptor plate face by approximately 5/8” it means that the planet carrier and uni-directional clutch have become mis-aligned. In this case remove the unit and re-align the splines."

Yeah I have come across that, I am 90% certain it is the splines, they are pain to realign. Oh how I wish someone had design a special tool for this. Oh well

[cleverusername]

It is very dumb design, all that complexity and weight, when the same job could be done with an of gear in the box.

I think that greatly depends on what the job you want it to do actually is and how you'd go about getting another gear in the box.

A sprint overdrive box weighs the same as a 5 speed rover box.
It's got another gear (the really useful one) or even two if you want.
You need to take your foot off to change gear with a 5 speed.

The problem with the overdrive is you are adding a whole new electrical and hydraulic system that can go wrong. Plus it does weigh a surprising amount, I was amazed how heavy it is. Whereas a 5 speed achieves the same end in a more compact package, without the extra systems that can fail. It hasn't got 2 extra gears, it has one, overdrive 3rd is pretty much the same as normal fourth.

There is also the nasty problem of the inhibitor switch failing and the overdrive being destroyed when you put it into reverse. There is a reason nobody uses them anymore, even on rear wheel drive cars.

[Jon Tilson]

Its a moot point....

A rover LT77 box is a right old mare of a box to rebuild and has a stupid oil pump with ceramic gears. I cant say I'd rather have it than a Sprint (triumph generic large car) box with o-d which weighs about the same with its alloy casing.

It clearly cost one heck of a lot more to build than the cheapo LT77. Yes the o/d and leccy bits can go wrong, but having had more than one LT77 ingest synchro teeth and stuff the oil pump, I'll take the Triumph box any day. I think nowadays its cheaper to rebuild bits and labour wise too. And the LT77 5th gear selector is an utter abortion as well...

I'm sure Ford 5 speeders are a lot better....

Jonners