How to: 1275 Marina engine + Sierra Gearbox?

Davros · Post by **Davros** » Sun Jul 29, 2007 9:30 pm

OK Peaple. I've got a reconditioned engine and the gear box out a J reg serria. Joining the two togeather for less than the £350 kit.If anybody who has done this has got any tips please reply.
questions
1 Chop the Minor gearbox down to length and attache a plate that fits the seirra gearbox or use the Sierra and make a plate to fit the engine ?

2 Clutch plate. Machie the ford flywheel to fit the engine or is there a clutch plate avileable that will fit the morris flywheel Gearbox splines?

3 Length of gearbox drive shaft. chop the front bit off?

thats it for now . Will report on progress

Post by **Matt** » Sun Jul 29, 2007 10:18 pm

Has the engine got the marina backplate/flywheel?

Davros · Post by **Davros** » Mon Jul 30, 2007 1:22 pm

No .When i used the engine before i fitted the minor flywheel and clutch cover. I may have the marina flywheel around somewhere . Is that the one to use?

Post by **dunketh** » Mon Jul 30, 2007 4:50 pm

No chance of any help from your Dalek minnions?

Sorry I cant offer any help on this but I'll be interested in how you get on.
I would imagine its the large cost of the 'kits' that put most people off.

Post by **bmcecosse** » Mon Jul 30, 2007 9:10 pm

I suspect you will need to use the Marina flywheel to get a clutch plate that will fit the Sierra box input splines. This all sounds SO much work - just to get a 5th gear! I suspect it would be a whole lot easier to just use a Sierra engine with the Sierra box !!

Post by **bigginger** » Mon Jul 30, 2007 9:16 pm

???????? It does?

Davros · Post by **Davros** » Mon Jul 30, 2007 9:19 pm

Dunketh, Its having just the one withered arm thats the real bugger!

bmcecosse, Believe me putting the serria engine in is more work anyway where's your sense of adventure

Matt I've found the marina flywheel and cover and it is thecorrect size for the serria clutch however the minor gearbox will not fit over.

i'll keep playing

Post by **bmcecosse** » Mon Jul 30, 2007 10:05 pm

Which is why a special bell-housing is required - which costs a small fortune !!

Post by **Matt** » Mon Jul 30, 2007 10:15 pm

Im shortly going to be investigating using the marina bellhousing to get a 5spd

Post by **Rich_T** » Mon Jul 30, 2007 11:59 pm

20yrs or so ago, I did exactly what youre asking about. I dont remember which ford gearbox we used but i do remember it had a big bellhousing on it so probably wasnt a type 9. Anyway, I stripped a minor box of all its inards and had a machine shop cut the bellhousing off the minor box. then the minor bellhousing was drilled to mate with the Ford box, I think a spacer was required between the box and bellhousing. The engine was from a Marina so needed front and back plates from a Minor/Midget. From memory I definately used a Midget flywheel and clutch cover, converted to hydraulic. The centre plate and flywheel bush escape me as to what was used, I do however remember spending ages in the stores at our local motor factors measuring up various plates to get the correct diam along with the ford splines.
In short it can be done fairly easily, at the time I was 16 yo so was still at the begining of my learning curve.

Rich

Post by **bmcecosse** » Tue Jul 31, 2007 10:27 am

"was still at the begining of my learning curve" - ie Young and foolish!! So - how did it all work out, and where is the car now ?

Matt - I have just 'acquired' an LT77 box - the very strong Rover SD1/TR7/Discovery/Rover V8 gearbox. A bell housing to use this box on an A series engine would be good ! Any ideas ?

Post by **Rich_T** » Tue Jul 31, 2007 10:43 am

The cars still mine, it worked well, though did get changed after about 4 yrs for a Fiat twincam.
Young yes, foolish no!
Rich

Post by **Kevin** » Tue Jul 31, 2007 2:32 pm

Matt - I have just 'acquired' an LT77 box - the very strong Rover SD1/TR7/Discovery/Rover V8 gearbox. A bell housing to use this box on an A series engine would be good ! Any ideas ?

Roy didnt Robbins from Somerset say he had this gearbox fitted to his car, I did ask at the time how it was done but I dont remember seeing what the reply was.

Post by **paulhumphries** » Tue Jul 31, 2007 2:53 pm

bmcecosse wrote:
Matt - I have just 'acquired' an LT77 box - the very strong Rover SD1/TR7/Discovery/Rover V8 gearbox. A bell housing to use this box on an A series engine would be good ! Any ideas ?

There are numerous different versions of the LT77.
There are different car and van / Land Rover type ratios as well as input shaft lengths and actual gearchange mechanisms.
It's actually an easy gearbox to work on and comes apart as a complete gear assembly rather then you having to feed individual gears and shafts into a casing.
That means even if you have the wrong input shaft there is no problem swopping.
I've got several of these lying around comming off Range Rover / Discovery, LDV van and Defender - all are different.
I suspect the LDV version bellhousing and input shaft (same as Defender) is the one to try modifying to fit an A Series with SD1 gearchange mechanism.
I reckon the easiest way is going to be make a custom backplate for the engine rather than adapt a bellhousing.
That would then mean probably having to machine the flywheel to take the input staft bearing as it's a lot larger dia then the Minor shaft.
The LT77 started as a 4 speed in 1950/60's Jaguars and was then developed into a 5 speed at a later date. (Jaguar didn't, as far as I know, use it in 5 speed format).
It's "OK" in a van or 4x4 but no where near as nice as the Type 9 Ford unit.
It'll handle power but isn't the best choice and even Land Rover / Range Rover / Discovery V8's moved onto a better (R380) gearbox due to the LT77's failings.
If you want any measurments off a LDV version let me know.

Paul Humphries

Post by **bmcecosse** » Tue Jul 31, 2007 3:06 pm

I agree - a special backplate (maybe modified Marina backplate) will be a lot more 'affordable' - provided the bell housing used is the correct length to allow the gearbox input shaft to reach the crankshaft. The support is in the crank tail - not in the flywheel.
Is there a serial number etc on the gearbox that will tell what type it is ?

Post by **paulhumphries** » Tue Jul 31, 2007 3:31 pm

bmcecosse wrote:I agree - a special backplate (maybe modified Marina backplate) will be a lot more 'affordable' - provided the bell housing used is the correct length to allow the gearbox input shaft to reach the crankshaft. The support is in the crank tail - not in the flywheel.
Is there a serial number etc on the gearbox that will tell what type it is ?

On reflection the input shaft is easy to remove (like I say quite a nice gearbox to work on) so maybe having it's dia machined down to fit into the crank is going to be the way to go.
Ashcroft's is one of the main specialists and if you search their web site there is various information including how to identify some of the versions.
http://www.ashcroft-transmissions.co.uk/

If you look at
http://www.roversd1.nl/sd1web/index.html
you can find additional information including a stripdown / rebuild of the LT77

Paul Humphries

Davros · Post by **Davros** » Tue Jul 31, 2007 4:48 pm

Thanks to Rich T for his information.several other peaple have said machinig down the minor box is the way to go so i think thats my next move.
There is a company in sherbourn that makes clutches so i'm going to contact them to see if there is aclutch plate that will fit the minor flywheel/ ford splines

Post by **bmcecosse** » Tue Jul 31, 2007 8:51 pm

Thanks Paul for these leads for the LT77 box!

Davros · Post by **Davros** » Thu Aug 02, 2007 10:53 pm

We had a long discussion about this at the Devon branch meeting. The guys that have already done the conversion use the minor gearbox cut down and a backplate to fit the ford box. The bolts to the box can either be on the inside or the outside depending on how it's made. The seirra clutch fits the minor flywheel and clutch housing if the two dowels are removed.( the Marina box bell housing is to big to fit between the chassie legs and intrudeds into the car). the minor clutch linkage can be used if an additional support bracket is made or you can use hydrolic cylinders.
I''ll be in the garage this weekend checking this in

formation out and will let you know

Post by **jonathon** » Fri Aug 03, 2007 6:44 am

I presume that you will be using an ally backplate, and tig welding this to the cut down bell housing. How are you measuring the total length of housing required, and how are you going to make sure that everything is welded up square. Whilst you are using the tig welder why not make up an alloy bracket for a hydraulic slave cylinder. beware though that the Minor bell housing is not a partculary pure alloy. B'ham Minor center employed your route to the conversion and had many issues of the plate being off center and square as a result of heat sink, which put the box in an incorrect position causing premature wear if the box and spigot bush. The main issue though was that the adapter plate often split away from the bell housing.
Whilst I admire your thrill for a challenge, this project has been sorted, by engineers over the last 15 years, so why try to re invent the wheel, or at least ask those who produce the current very good bell housings about the pitfalls and ideas behind their product. Just seems an awfull amount of energy being spent in re assessing a product which has been already sorted and refined. Realistically the cost of the bellhousings is not prohibitive or if it is , should you be considering this project at all, I applaud your efforts though and wish you well.