One-Point-Five Gearboxes

[Mabel]

Mabel's gearbox ix suffering a bit. Synchro has gone on second and overall it's getting noisier and noisier and before any bright spark asks, yes it's got oil in it.

So, from time to time gearboxes become available and just wondered if any 1.5 gearbox can replace any 1.5 gearbox? For instance as I have MK I do I have to get a a MK I gearbox or are those from from MK IIs and MK IIIs compatible and a straight swop?

The problem is if they'e not then sometimes the sellers doen't know which model it's from. Any identifying features that could be looked out for?

[noddy]

Graham,

A straight swap is possible - but there is one thing to watch out for ...
The oil filler plug on the side cover was moved during production - on early cars (? all Mk1s ?) it is quite far forward - but later cars it was moved 4 inches further back and up a bit. This means access to the filler could be impossible - without cutting a new hole in your transmission tunnel!
Later gearboxes were also much more robust!

Roger

[Mabel]

Roger, If I have to cut a new hole and patch the original then so be it. That's really not a problem.

I don't know why but there's something going on in the back of my mind that keeps coming back to me that says there's an issue with the number of splines and also fixing points. I could be wrong though.

[canuck]

I have to think that a Riley specific transmission is straight swap for swap as Roger states. 

However, what did the chaps & bonnies at ADO do with the later build Riley transmission?

 

In the detail plate above there was a change point along the way for our Riley, that being the transmission cross member and mountings? Having only ever seen 3 other Riley in my life, and all MK 1 cars I do not have the experience or exposure that you home market chaps do. This lower RH viewed type is fitted to my early MK1 Riley as I believe Grahams' Mabel is. . Practically I think it easier to source a Riley specific gearbox, MK 1 specific? 

Over here we have little source so I am always looking for alternative, an for purpose of discussion; in the detail above the lower RH cross member and mount leads me to believe that any low starter motor gearbox from an early MGA may fit as well?  I recognize that to use a MGA transmission it will not be 'plug n play' but rather some 'mix n match' will be needed. One, the MGA gear lever extension will be swapped out for the simple Riley gear lever attach. The bell housing will require a notch at top to clear the steering rack of the Riley.

So did I serve to confuse? probably, so best to search out a Riley transmission for replacement. The caveat being it may be like that Forest Gump box of chocolates, you never know what you are going to get. FWIW good quality replacement synchromesh rings and lay gear clusters are a devil to have in NA for non synchro first transmissions.

Back to you lot

Salut

B

Edit:

Splines concern is probably at first motion shaft. This can be addressed by swapping your existing clutch disc if you need. There is early 10 spline and later 23 spline clutch disc.

B

  

[2robert4]

I have been toying with this for some time as the second gear syncro has all but disappeared and the Laygear bearings are starting to get noisy on my gearbox. Generally Mk2 Gearboxes onward have the later type cross member and a 23 spline center plate but the filler is in the same place, MGA early gearbox's have a dipstick which cant be used on 1.5 unless you cut another hole in the floor pan and the filler is in the wrong position. One of the other problems will be the speedo gearing which will be different but the with the later box you can if my memory serves me right get three different driven gears sourced from MGB I think its 26 teeth 28 teeth and 30 teeth these combinations are used with non overdrive, overdrive and auto box's. I am currently looking at this and have obtained all gears available for when I do get around to doing it plus I am experimenting with drive gears for the early gearbox/later speedo head combinations so that you don't have to send the Head away for a recalibration which is expensive as just changing the drive gear is easy and cheap compared to recalibration.I am also looking into early gearbox stay rubbers which the club do not have stock of but are I think the same as MG ZA/ZB this site NTG Motor services www.mgbits.com/contents/en-uk/d171_02.html has the bar complete with rubbers plus the rubbers on their own. I will report back once I have completed these tasks but the cold weather does not make me feel like doing anything just now. Hope these comments are of some help.
Cheers
NP

[blaxy]

Probably a stupid question, but they say, if you don’t ask……!

If you have a spare gearbox (and I do) is there any way of testing its operation/synchromesh before you spend the time and effort fitting it to the car – maybe only to find out that it’s not any better than the one that was fitted?

Dave

[2robert4]

Unfortunately there is not too much you can do with out stripping it and examining the syncro cones and the Hub detents and springs plus the usual Laygear bearings etc. But you can drain any oil that is left in the gearbox through a filter cloth looking for debris then remove the side plate to check for corrosion chipped teeth on the gears and worn bearings. Select the gears one by one and check the syncro cones for excess wear and damage, turn the input shaft and feel for roughness then rotate the output shaft to check for any roughness as this is indicative of a worn bearing these jobs can be done with out stripping the gearbox and might save you some grief. Don't forget to change the input and output shaft seals, speedo drive seal and any gaskets you can easily get to this may save you from oil leaks later. Don't forget if the Gearboxes are not like for like i.e early 10 spine Gearbox to a later 23 spline gearbox and visa versa you will need a new clutch center plate and gearbox mounting cross member plus the speedometer drive ratios will be different.
Hope this helps
NP

[blaxy]

Thanks for that NP that is really interesting, I will look into that when I hopefully get more time, as the better weather and longer daylight hours arrive.  In the meantime I will continue to double clutch when changing down to 2nd.

I always though that the 'stronger gearbox' (with the 23 spline shaft) were introduced on the MkIII from November 1961, but stand corrected if I am wrong

Dave

[2robert4]

No you are indeed correct thank you for pointing out my keying error.
Kind regards
NP

[Mabel]

Was Synchro failing on 2nd gear a standard fitting and guaranteed to fail by the time it left the factory gates?

[wunpointfyve]

Mabel,

I know this is a late answer, but I've only just joined, thinking to get back into 1.5s after a 20-year gap.

Anyway, I think the 2nd gear synchro fails because it's used almost twice as often as the other two, especially as its a low enough gear to start with on the level. If they'd fitted a synchro on first this defect might never have happened.

[2robert4]

Further to my post on the 17th of February I have now fitted the MG ZA/B Gearbox Stay and rubbers with some success although the bubbers are not as thick as the originals they have performed well over the last 1100 miles.
Hope this info may be of some use.
NP