Where to find help when you want to change major units on your CF - engine, transmission, brakes etc. - or upgrade earlier models to later specifications.
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Overdrive

Post by Grimble » Sun Sep 18, 2016 1:26 pm
Joined: Sat Nov 28, 2015 12:01 pm
Posts: 53
Hi
i am going to try and fit this overdrive unit to my gearbox. Any ideas if this is possible for an amateur? i have never worked on a gearbox before.
i currently have the same 4 speed box fitted to my CF and i also have the propshaft to go with the overdrive.
Anyone done this before? Anything i should know?
thanks

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Re: Overdrive

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Post by VDUB384 » Club admin » Sun Sep 18, 2016 6:07 pm
Joined: Wed Sep 12, 2012 9:01 am
Posts: 1253
Usually the main shaft in the gearbox is a different one when you have an overdrive unit fitted at least it has been on the gearboxes I've worked on in the past with overdrive units on
Dave
Whilst good maintainece is the best prevention"If its not broken don't fix it."
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Re: Overdrive

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Post by Phil Bradshaw » Club admin » Mon Sep 19, 2016 1:24 am
Joined: Sun Sep 02, 2012 7:15 pm
Posts: 3308
What's wrong with the gearbox that's attached to the overdrive now?
  • What is real is not the external form but the idea, the essence of things. Constantin Brâncuși
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Re: Overdrive

Post by Grimble » Mon Sep 19, 2016 8:40 am
Joined: Sat Nov 28, 2015 12:01 pm
Posts: 53
its a good question Phil. I was told by the previous owner that the bell housing cracked in several places. sounds like the bolts holding it onto the engine were not tight. i was worried that this might have damaged the rest of the box and was hoping that it would be an easy swap to fit the O/D to my box.
looks like i am going to do what you have suggested Phil and go from there. Fit the whole lot and find out.
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Re: Overdrive

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Post by VDUB384 » Club admin » Mon Sep 19, 2016 8:56 am
Joined: Wed Sep 12, 2012 9:01 am
Posts: 1253
What's stopping you swapping bell-housing over then putting the gearbox complete with overdrive on that would make more sense
Dave
Whilst good maintainece is the best prevention"If its not broken don't fix it."
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Re: Overdrive

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Post by Phil Bradshaw » Club admin » Mon Sep 19, 2016 10:54 am
Joined: Sun Sep 02, 2012 7:15 pm
Posts: 3308
If the clutch housing was an earlier type then cracks wouldn't be unusual. Later clutch housing is a straight swap but make sure that the two 1/2-inch caps and the end of the layshaft at the front of the transmission have a good coat of sealant before assembly to prevent oil leakage.

In the photo it looks like there's a hole in the top of the overdrive where the breather should be. Original fitting is like the breather on the extension housing of the non-overdrive transmission (i.e. hollow stem with loose fit cap) but larger diameter if I remember correctly.
  • What is real is not the external form but the idea, the essence of things. Constantin Brâncuși
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Re: Overdrive

Post by Grimble » Sun Oct 09, 2016 8:49 pm
Joined: Sat Nov 28, 2015 12:01 pm
Posts: 53
Well i got it fitted today using my bell housing and keeping the overdrive unit attached to its original gearbox. I will finish it tomorrow, fill it with fresh oil, fit a breather and go for a quick road test. Fingers crossed eh :D

One problem that i have already found is that the speedo cable for an o/d must have had another type of fitting because mine will not connect. Anyone know if they are avaliable new or where to find them?

I will post some pictures when i get a chance. It took me six hours in total today and was an easy job with no problems at all. Only bit that required some thought was the rear mount having different fixings. I removed the 1/2" studs from the mount and used bolts into the ally O/D housing. Other than that it was an absolute joy to work on. :) most pleasant gearbox change i ever did :thumb:)
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Re: Overdrive

Post by Grimble » Mon Oct 10, 2016 8:14 pm
Joined: Sat Nov 28, 2015 12:01 pm
Posts: 53
O that didn't go so well :(
1st 2nd and 3rd are fine, in fact very smooth and quieter than any CF box i ever used. i was actually quite pleased for a while. That is until i selected 4th and it popped straight out. dam shame as the other three gears are beautiful
Could this be a selector fault or is it something more serious? i put fresh oil in it :oops:
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Re: Overdrive

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Post by Phil Bradshaw » Club admin » Mon Oct 10, 2016 8:27 pm
Joined: Sun Sep 02, 2012 7:15 pm
Posts: 3308
Jumping out of top gear usually is due to worn synchro dogs on the input shaft and 3/4 synchro sleeve or a loose or cracked 3/4 synchro hub or a combination.

Wear in the clutch spigot bearing in the back of the crankshaft, transmission front bearing, mainshaft spigot and, or, roller bearing/s can be a contributory factor.
  • What is real is not the external form but the idea, the essence of things. Constantin Brâncuși
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Re: Overdrive

Post by Grimble » Sat Sep 16, 2017 8:19 pm
Joined: Sat Nov 28, 2015 12:01 pm
Posts: 53
All sorted now and i must admit that the overdrive is an essential component. My CF is now much more usable on motorways and long journeys. win 8-)

turned out that the synchro hub for 3rd and 4th was borked but i bought a new one from ebay for £30 and had it fitted by a friend.
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