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Overdrive in a 4 speed?  Rating:  Rating
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 Posted: 10-13-2005 04:46 pm
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Lawrence Tod
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I had purchased a clutch ,pressure plate, pilot bearing and release bearing
a while back, just to have on hand for 11211.

I was examining the article in the "tech" section regarding the clutch replacement. From the pictures I have seen I am a little concerned. My gear box has a "solonoid " with a wire pigtail hanging out of it. I suspect this is an overdrive unit. Does anybody else have one of these?

If not, I suspect I will have a spare clutch..etc. for a long time.

If nobody knows what I am speaking about I will post a photograph.

Thanks

Lawrence

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 Posted: 10-13-2005 11:18 pm
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Tony Hollart
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The overdrive gearbox is easy to spot as it fits to the back of the standard gearbox and is large. The " solenoid " you speak of is not the reversing lights switch is it?

None of the JH came out with the overdrive gearbox but there are lots of cars that use the Hillman / Rootes gearbox, which means there are gearboxes that can be fitted to the Jensen Healey bellhousing and installed into the Jensen.

Attached is photo of a gearbox out of a Sunbeam rapier with the overdrive attached.

Not my car or photograph so cant give any other details. 

Tony H

Attachment: rapier gearbox.jpg (Downloaded 245 times)

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 Posted: 10-14-2005 02:04 am
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Lawrence Tod
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O.K. So I guess I have a big problem now.
How much slower does that make my JH than everbody elses.

The first thing that comes to mind is...what are the gear ratios of all the gears in the Holden box compared to the stock unit.

My first thoughts are..on the market place page there is a guy with a very early JH in England that is very rusty, and sounds like it won't see the road again unlesss somebody is willing to Hemorage Money at it .
This English Healey would obviously be RHD and therefore better suited to where I live, so perhaps I could merge Healeys . Is this frowned upon ? Can you imagine shipping a "parts car across the ocean!?
My accountant will have a fit!

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 Posted: 10-14-2005 07:23 am
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Tony Hollart
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Lawrence, if you have got an overdrive gearbox this is a good thing rather than a bad. If the drive shaft fits ok and connects to the diff, then you dont have a problem. The overdrive box has been retrofitted from cars like the Rapier in the photo to the Jensen. Its a good move as typically they reduce the revs in 3rd and 4th by somthing like 25%. The only reason overdrive gearbox has gone out of favour is because of the availability of 5 speed boxes. As far as I know and I am sure I will be corrected if wrong is that the Jensen 4 speed box is 1:1 ratio in top and so is the Getrag 5 speed box BUT, the Jensen with the five speed box were fitted with a slightly taller diff ratio ie 3.45 for the 5 speed and 3.727 for the 4 speed. The overdrive box in MG B's and such like make them much more comfortable cruisers on the open road.

As for using two cars to make one, this is a fact of life that the bad cars get used for parts. The cars were very much put together to minimise assembly costs as they use many big flat sections with herring bone pattern to provide rigidity and stop drumming of panels. Then there must have been quite big money tied up in the tooling to press the bonnet and front wings becuase of their size.

I purchased my car three years ago and it was in a poor state, but with attention to replacing panels and rust removal and rust prevention it is coming together as a smart car that I am looking forward to driving in. All the best with your project.

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 Posted: 10-14-2005 01:48 pm
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Lawrence Tod
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Tony;
So your line of thinking is this is a good thing rather than a bad?
So maybe I'll hold off calling this fello in U.K.
Any ideas how to hook up the overdrive. Is this simply something I supply a constant 12 volts to. Or do I need to rig a switch?

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 Posted: 10-14-2005 02:28 pm
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Mark Rosenbaum
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The overdrive solenoid should work off +12 volts.  Ideally you would use two switches to control it: one on the dash or shift knob, with power supplied by the ignition switch.  The output of this switch would feed a 3rd/4th gear switch mounted on the transmission linkage cover (this is directly opposite the backup lights switch).  The output of this second switch would go directly to the solenoid.

This arrangement prevents damage to the overdrive from excessive torque in the lower two gears.

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 Posted: 10-14-2005 03:30 pm
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Lawrence Tod
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Oh Scary!

Thanks Mark, so how did Holden configure this originally,
The switch close to the reverse switch was this automaticically engaged like the reverse light switch, so it suplied power when a part of the shift mechanism came in contact with it?

I called the guy in Essex from the marketplace add, with the very early Healey. He wasn't home, left message perhaps he'll get back to me.

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 Posted: 10-14-2005 05:55 pm
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Mark Rosenbaum
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Don't know how Holden did things.  The way I described is the simplest safe approach.  If you don't trust your switches to handle the current needed by the solenoid, then you can have the switches control a relay which in turn controls the solenoid.  You could also, perhaps, add a throttle position sensor such as the one used in the Austin Healey, to switch out of overdrive under full throttle conditions (much like the 'kickdown' in an automatic transmission).

The shift linkage cover has a boss for the overdrive switch and the linkage itself has the necessary protrusion to operate the switch.  As you surmised, the overdrive switch is automatically closed whenever the shift lever is moved to the 3rd or 4th gear position.

The shift linkage cover is supposed to be drilled and tapped for the overdrive switch, but this may have been neglected in some cases -- and if so, drilling and tapping an accurately located hole would solve the problem.  The overdrive switch and backup lights switch are identical.

There are several gear sets that can fit into the basic Sunbeam/JH transmission case, and these were listed in one of the other posts in the Engine & Transmissions category on this site.  The only way to know which set you have is to select first gear and count turns in versus turns out, or to take things apart and count gear teeth.

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 Posted: 01-03-2008 01:17 am
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mark lees
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hello my car is # 13076 and it does have an overdrive  from what i can find out it is a d type laycock de normanville and evryone i have talked to say they didnt come with them any info would be appreciated as i understand that it is quite an ordeal to put  them in [new transmission mainshaft etc] i am trying to find out more info from previos owners. my purchase price was 100 dollars and i have since fixed the rear wheel bearings and welded in new floors and frame rails helluva job but i had it running the day i dragged it home,quite a snappy sounding little motor. hope to hear from anybody on this topic    thanks

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