Fairey overdrive wont Bolt down

P38dave · May 13, 2020

Hi all after removing my overdrive and doing the seals upon refitting try as we might the od just will not Bolt down the nuts only go so far leaving about quarter inch gap between the od and tb mating surfaces iv had the tb cover off and the input gear is meshed but it just will not go any further. Another thing I found was the drain plug threads on the od have been stripped and the plug was glued in does anyone know the best way to sort that? Cheers Dave.

jamesmartin · May 13, 2020

P38dave said:
Hi all after removing my overdrive and doing the seals upon refitting try as we might the od just will not Bolt down the nuts only go so far leaving about quarter inch gap between the od and tb mating surfaces iv had the tb cover off and the input gear is meshed but it just will not go any further. Another thing I found was the drain plug threads on the od have been stripped and the plug was glued in does anyone know the best way to sort that? Cheers Dave.

what seals ? recoil kit will sort the thread issue

P38dave · May 13, 2020

All the seals were changed as it leaked from everywhere

rob1miles · May 13, 2020

I seem to recall the tab washer on the mainshaft nut can be an issue. Also have you checked that the small bush is not full of grease?

P38dave · May 14, 2020

Cheers for the info il have a look at the tab washer and I think there may be some grease where the bush sits in as I greased the splines not thinking not to get any grease on the bush!

P38dave · May 14, 2020

Should also add you can move the input gear in and out on the mainshaft about 1mm is this normal?

jamesmartin · May 14, 2020

P38dave said:
Should also add you can move the input gear in and out on the mainshaft about 1mm is this normal?

no and have you had the castleated nut off because the 3 tabs need bending over eventhough only one fits in a slot

Blackburn · May 14, 2020

The locknut tabs usually need reducing a little for fairey instalation.
Fitting instructions.

P38dave · May 14, 2020

Haven't touched the clutch sleeve or the lock washer I did have a problem with a bearing race being stuck the one that holds the mainshaft the one that's visible with the rear ball bearings and gear removed a needle bearing sits on it

rob1miles · May 14, 2020

My point with the grease was a little is good but too much and it forms a hydrualic lock. Any pics, it would help.

P38dave · May 14, 2020

Don't know if you can see on the pic but the splines on the mainshaft of the od seem badly worn as they are sharp

rob1miles · May 14, 2020

I would definately replace the "clutch" part with the male splines. These seem to be quite soft and designed to wear first. There's a needle bearing that's worth changing at the same time. Look carefully at the splines in the OD as they can be worn behind the bit you can see so they look OK at first sight but in reality the splines are very weak. The bad news is that means a new input shaft, that's what happened to me. One good reason to change the "clutch" / coupleing is to try to prolong the life of the splines in the much more expensive shaft.

P38dave · May 14, 2020

Yes that's what's Im worried about the splines in the od that as you say look OK at first glance mabe first 2mm from the edge but are razor sharp after that. TBH I just rant rid of the od after the trouble it's caused so if anyone has a standard gear and cover for sale let me know

jamesmartin · May 14, 2020

P38dave said:
Yes that's what's Im worried about the splines in the od that as you say look OK at first glance mabe first 2mm from the edge but are razor sharp after that. TBH I just rant rid of the od after the trouble it's caused so if anyone has a standard gear and cover for sale let me know

they nearly all have worn splines but aslong as it drives keep it, id hhave a gear and cover, you could have till necessary,.they can be hard to refit , try jacking a rear wheel up and have someone turn it whilst you try fitting over drive

P38dave · May 14, 2020

I think il just stick a gear on til I get round to the od thank you very much for the offer JamesMartin but il just use the missus car for now

rob1miles · May 15, 2020

Trouble is there not an OD that's less than around 40 years old now so its a case of nursing them along or major rebuilds.

P38dave · May 15, 2020

Rob that's the thing I don't trust it I don't want to loose drive. The fairey is a weak unit doesn't hold enough oil splines made of cheese leaks needs weekly oil checks noisy etc etc. Though in saying that they do increase top speed and keep the revs down especially in the 2.25d.

rob1miles · May 15, 2020

I rebuilt mine around 4 years ago - the splines were exacltly like yours so it needed a new input shaft, drive clutch, the needle breaings, all the seals and the circlips. i left the big bears as is and the out put and lay gears were worn but usable. Its now done 10,000 miles in a LWB with 3.3L Perkins and its not used any oil and works great. If I were you I would strip it and fix all the damaged parts, there's no point in struggling on with something you don't trust. Obvouly you can take it off and get £2-300 for it as is, but try driving without it first, the noise goes up a lot and the cruising speed drops by about 8mph which is a lot in a Serie.

P38dave · May 15, 2020

I never went as far as stripping the input shaft as I couldn't get the needle roller race off it not even with heat. I would like to rebuild it at a later date somehow as it does make cruising more tolerable

steve2286w · May 15, 2020

Tips in the fitting instructions above if it does not fully engage due to meshing problems
Did you try them

Fairey overdrive wont Bolt down

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