10 replies to this topic

[Gwallace]

I've search everywhere and cant find any information on the compatibility of 3/4 Synchro parts. ( probably for good reason as i'm attempting something which defies logic :) ) So i'm hoping someone here might have hands on knowledge of the differences.

 

I'm putting together a 997 cooper engine and box. I have an old 3 Synchro 850 engine and box which i have stripped down. I also have the empty housing of a 4 Synchro aluminium remote gear change box (correct for the 997). The original plan (as the ratios are the same) was to put everything out of the 3 synchro into the 4 synchro on the idea i'm not too bothered about not having synchro on first.

 

1. is this even possible?

2. Does anyone know of any bits that are not compatible?

 

I've found lots of videos of putting a+ components into pre A+ box's with a little fettling but nothing for pre A+ 3/4 synchro

 

I'm trying to make sure i'm buying the right bearings etc I've been trying to research enough to give me a little re assurance before ordering MSG17 from Mini spares

 

http://www.minispare...|Back to search

 

I's assuming the synchro gears are the same for 3/4 but assume is a dirty word. or at least the word i say before i find out I've screwed it up.

 

The first motion shaft bearing are a bigger O/D but i'm hoping the ID is the same. Putting the two cases next to each other there seams to be very little difference other than a few oil way machining details.

 

All comments welcome, I'm really struggling to find any information on this one.

 

Thanks in advance

 

Gregg

 

[nicklouse]

talk to john at Guessworks IIRC he has done this.

[Spider]

Short Answer is No.

 

About the only parts that interchange between the 3 and 4 Synchro Boxes is the Diffs, the Final Drive Gears and the Speedo Drives.

 

The 3 Syncho Laygear is (from memory) 1.00" shorter from Thrust Face to Thrust Face than that fitted to the 4 Synchro and so the cases are vastly different between the two.

 

The ratios are also different between 3 and 4 Synchro boxes.

 

The correct Gearbox Case Casting No. for a 997 Cooper is 22G68. The early 998 Cooper and same period 850 Minis, shared the same Gearbox cases, but only the Coopers had the right ratios.

[Retroman]

Its mission impossible

 

The laygear, mainshaft and 1 motion are different lengths and is reverse gear is different, the layshaft is shorter and parallel

 

The double roller bearing is smaller in a 3 syncro too and the bearings inside 2nd and 3rd are big diameter un-caged needles

 

Your 4 syncro remote box was never fitted to the original 997 they were all 3 syncro

 

Just rebuilt a 3 syncro for a really nice '66 original 998 Cooper

 

As Spider said they share the diff, the speedo gears and thats about it

 

You answered your own question in your 1st sentence.... you can only defy logic with logic

 

As you are using a 4 syncro box just use a 4 syncro gearset

[nicklouse]

talk to john at Guessworks IIRC he has done this.

mm actually I might have been thing of something else.

[Retroman]

 

talk to john at Guessworks IIRC he has done this.

mm actually I might have been thing of something else.

 

 

Did wonder...

[nicklouse]

 

 

talk to john at Guessworks IIRC he has done this.

mm actually I might have been thing of something else.

 

 

Did wonder...

 

may have been later 4 syncro gear set into an early 4 syncro case was late last night. but I know it was some gear set that would not normally fit in some case.

[Spider]

 

talk to john at Guessworks IIRC he has done this.

mm actually I might have been thing of something else.

 

 

I suspect what you may have been thinking of was fitting a 3 sychro diff cap on a 4 synchro box or viki-verka.

[nicklouse]

 

 

talk to john at Guessworks IIRC he has done this.

mm actually I might have been thing of something else.

 

 

I suspect what you may have been thinking of was fitting a 3 sychro diff cap on a 4 synchro box or viki-verka.

 

sure it was not that. it was definatly a gearset.

[Cooperman]

It is possible to fit Cooper/Cooper 'S' ratio gears into a standard ratio box of the same basic type, i.e. a 4-syncro or a 3-syncro, but not across the types.

For example, my 1990 Cooper 1275 has been fitted with gear ratios as for a late model Cooper 'S' Mk.2 or 3 with the 4-syncro Cooper remote gear-shift 'box. Lovely ratios they are too.

[Gwallace]

Thanks everyone for your input. It is really appreciated. I think i will just see if i can get my hands on a 4-syncro box for parts. The last month has been a bit hectic and so i haven't made much progress but hopefully the Christmas break should give me a chance to find a good donor.