The Triumph Dolomite Club - Discussion Forum
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Auto Overdrive
http://forum.triumphdolomite.co.uk/viewtopic.php?t=33986
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Author:  AlanH [ Sun May 20, 2018 11:03 pm ]
Post subject:  Auto Overdrive

Just been reading in Club Torque about the finishing of Charlie Deards' beautiful 2500S at the Practical Classics show.

The last paragraph says 'the overdrive on the BW65 auto box should be completed by Moordales in the next few months'.

As the owner of two 1850s and one Sprint auto I shall follow this with great interest.

Author:  harvey [ Tue May 22, 2018 6:54 pm ]
Post subject:  Re: Auto Overdrive

Making a standalone overdrive is quite easy if you have access to, and ability on, machine tools, and room in the tunnel to fit it.

Author:  Galileo [ Tue May 22, 2018 8:11 pm ]
Post subject:  Re: Auto Overdrive

Overdrive Spares will happily supply you with a standalone unit and so with a little tunnel modification...
Image
http://www.odspares.com/phdi/p1.nsf/sup ... ent&part=4

Author:  xvivalve [ Tue May 22, 2018 8:18 pm ]
Post subject:  Re: Auto Overdrive

I have overdrive units amongst Jonners' things...

Author:  Carledo [ Tue May 22, 2018 8:46 pm ]
Post subject:  Re: Auto Overdrive

I reckon you'd have to bolt that to the front of the diff to get it in a Dolomite! The sheer size of the BW65 and the "choke point" in the Dolly bodyshell just aft of the removable tunnel would preclude any possibilty of mounting it at the front end of the tunnel. The sensible thing would be to replace the prop centre bearing with it, but, even if you WERE prepared to hack the shell about to fit it there, its right where the seats go! And bolting it to the diff would do wonders for the unsprung weight - NOT!

My solution is better, if not much easier, i've got the Aisin Warner ECU controlled, 4 speed, 3 range, overdriven autobox with lockup on 4th gear that goes with my Omega 2.2 16v motor. It's been a tight squeeze getting it in and the wiring was a total PITA, but i've not had to mod the shell in any way, so no risk of BIVA for me!

I'm just praying it was worth the effort! The 1.8 tonne air conditioned, power steered, 3.7 diffed behemoth that donated it's power train to the project managed to average 38mpg on a 300 mile, mostly motorway run shortly before I dismantled it. In the 1100kg Sprint with no PAS or aircon to drag it down and a taller 3.45 axle, i'm hoping for VERY relaxed cruising and fuel economy in the 40+ range - at least on a run!

Steve

Author:  Galileo [ Tue May 22, 2018 10:27 pm ]
Post subject:  Re: Auto Overdrive

Well that escalated quickly into an entire engine and box transplant! :lol:

Replacing the centre bearing would be worth a look but agree that bolting it to the diff would be a courageous choice!

Author:  AlastairC [ Fri May 25, 2018 12:42 am ]
Post subject:  Re: Auto Overdrive

Interesting - I was wondering about doing this with my Stag but was told that it isn't possible. Those who have (or have driven) an auto stag will know that they are a bit under geared and could well do with another cog when it comes to motor way driving etc. Would be great to hear more about this. Id be wrapped if an od can be applied to a stag auto box

Author:  xvivalve [ Fri May 25, 2018 6:50 am ]
Post subject:  Re: Auto Overdrive

Isn’t the auto’ ‘box shorter than the manual o/d ‘box? The prop is certainly longer, and by more than the width of the manual adapter plate which isn’t used...

The auto’ transmission tunnel is flatter than the manual, especially to the rear, so you’d need to adapt that, but surely it would fit? Isn’t there a rear extension housing on the back of an auto’ box too? I used to have one I. The garden that I could have experimented with, but I gave it away 🙁

Author:  soe8m [ Fri May 25, 2018 9:21 am ]
Post subject:  Re: Auto Overdrive

Nice to dream about this but I think it's the most strange and stupid idea to put an od behind an autobox. The lining up, the short propshaft involved, the modification of the body and the overall characteristics of an autobox of a non solid drive according the converter. Find a fourspeed autobox if you want an extra gear.

Jeroen.

Author:  xvivalve [ Fri May 25, 2018 9:54 am ]
Post subject:  Re: Auto Overdrive

Toyota, and others, have autoboxes with overdrive...

Author:  Mahesh [ Fri May 25, 2018 10:25 am ]
Post subject:  Re: Auto Overdrive

Quote:
Toyota, and others, have autoboxes with overdrive...
I know the Nissan Prairie had an o/d on a autobox, damn thing was smooth in operation
at high speed as well.

Author:  Carledo [ Fri May 25, 2018 10:27 am ]
Post subject:  Re: Auto Overdrive

Quote:
Isn’t the auto’ ‘box shorter than the manual o/d ‘box? The prop is certainly longer, and by more than the width of the manual adapter plate which isn’t used...

The auto’ transmission tunnel is flatter than the manual, especially to the rear, so you’d need to adapt that, but surely it would fit? Isn’t there a rear extension housing on the back of an auto’ box too? I used to have one I. The garden that I could have experimented with, but I gave it away 🙁
The 65 IS slighly shorter than a man/OD box, but only by an inch or two, but the loss is much greater than that as the BODY of the trans is much longer than the body of a non O/D manual and the tailshaft housing with speedo drive is correspondingly shorter, only about 6" long. Then there is the shorter mainshaft you'd have to make for the autobox and the adaptor housing too, I don't think it's a viable alternative.

Like Jeroen says, get a 4 speed box to start with......I did!

The Toyota/Mitsubishi Auto range nearly ALL have "O/D" but its not a true overdrive, just a 4th gear that can be locked out manually, its still operated by the same valve block as the rest of the transmission.

Steve

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