12 replies to this topic

[Johnmar]

Question regarding changing Final Drive 3.1 => 2.76

As my usage of our mini after restoration will be different than before and I expect to be using it 80% at 80-100km/h (50-60m/h)and I want to enjoy those trips I was contemplating on changing the FD from our '93 SPI from a 3.1 to a 2.76.

The latter was used by Rover in the MPI to reduce driveby noise as it lower the revs 12%  (2.76/3.11). I lknow it will mean that acceleration will be less nippy but I'm at the stage that I can use some comfort in the noise department next to the extra noise insulation that I'll try to incorperate during the restoration.

I can get my hands on a new 2.76 FD set (containing the 58 teeth Crown wheel and a 21 teeth pinion). From what I understand I will have change my speedo drive using a 15 teeth minn pinion and a 7 teeth spindle. (from what I read the we are talking here on the parts TXD10004(15 teeth) and TXF10001 (7 teeth).


My problem is: I've not been able to seperate my gearbox from the block as my flywheel does not budge. Have tried and killed multiple flyfwheel puller on this. So at the moment I cannot seperate my box from the engineblock.

My questions:

1. Has anyone been able using a 15 teeth speedo drive pinion from a 2.76 Fd  with a 7 teeth (blue) (DAM6028) from a standard 3.1 gearbox or do I really need to change this for a 7 teeth spindle (TXF10001)?
2. If I need to change the 7 teeth spindle from question 1, is there a way to do it without splitting the box from the engine?
3. If I can get away with Question 2, I still need to change the FD 21 teeth pinion. That one is fixed with a whopping 150lb/ft. Could I get away with locking the flywheel in order to block the box temporally or is the only way to engage 2nd and 4th gear as described in the article on minimania.com below?

(see: https://www.minimani...do_drive_ratios)

I'm not really looking forward to the following part of that article "Using a pry bar, or long screwdriver, push the 1st/2nd and 3rd/4th selector quadrants inwards. They will rotate towards the clutch end, and in so doing engage 2nd and 4th gears. Engaging reverse by sliding the gear away from the centre web and into mesh with the outer gear of the 1st/2nd outer track using a long screwdriver assists further."

I'm a total noob at the gearbox and I have to look op in the books what it even means so If I can steer away from that part of the selector quadrants and sliding the reverse alone, I'm much more at ease

If it is equally possible to lock up the box by locking the flywheel (with a locking bracket to lock the fly wheel bolted to the flywheel housing where the starter motor engages the fly wheel), I'd rather do that than try to operate on the box like described in the article.


If any one has any remarks/suggestions/experience they want to share, please do so.

 

 

[GraemeC]

You don't need to separate the block and gearbox.

 

The speedo gears are simply changed in the speedo drive housing - very simple.

The crownwheel can be changed by removing the diff - doing so also gives you the access to disengage the interlock spool and lock the box in 1st & 4th

The pinion can then be removed by removing the speedo drive housing.

 

Usually you need to use the correct pairs of speedo gears as the tooth profiles are different between part numbers

Edited by GraemeC, 16 November 2021 - 12:13 PM.

[Johnmar]

You don't need to separate the block and gearbox.

 

The speedo gears are simply changed in the speedo drive housing - very simple.

The crownwheel can be changed by removing the diff - doing so also gives you the access to disengage the interlock spool and lock the box in 1st & 4th

The pinion can then be removed by removing the speedo drive housing.

 

Usually you need to use the correct pairs of speedo gears as the tooth profiles are different between part numbers

 

Thanks GraemeC for this info.I'm getting more confident reading this info.

Heck:I've just bought the FD 2.76 set I have my eye on is a new one. And the seller can includes a matching set speedo drive (yellow) and speedo pinion so that should all match. So on the parts department it should be golden.
(now i ONLY have to find out how to disengage the interlock spool, lock the box in 1st and 4th, and how to unlock and engage the interlock spool (after having replaced the FD pinion).

Edited by Johnmar, 16 November 2021 - 05:48 PM.

[Spider]

To lock the Gearbox so you can get the Pinion Nut undone and then done up, it is as described, but without knowing what you'll be looking at it's a little hard to put just in to words. This may also help;-

 

 

But, before you get to this part, there's an interlock you need to remove (this prevents engaging 2 gears at the same time). When you take off the RH Side Cover on the Diff, you'll see a spring towards the bottom side of it (no, it won't fly out !), Remove that spring, then inside there, there's a ball bearing, use a magnet to remove that and these are in a small steel tube, take that out as well.

This then allows you to rotate the Selector Input Shaft 180⁰, after that, the selectors are unlocked and you'll be able to select 1st and 4th.

 

You should be right with this, but just check when fitting the Pinion that the C Plate that's bolted in the gearbox clears it.

[Johnmar]

Thank you Spider!!

This will help for sure!

[viz139]

Have to agree with all the advise already given.

The Mpi with the 2.7 FD produces 63hp. The SPi Cooper 62Hp but if you have the low compression SPi it only has 52Hp and that 20% power drop would have a big effect on drivability. 

Personally I have the 52Hp SPi and find it very comfortable at 100kph . I run a standard exhaust. I also use it to tow my Puck which is probably similar effect to higher final drive and not as much fun. 

[Magneto]

I run 2.76 final drive in my cars and I don't find it to be doggy around town, the reduction in revs on the highway makes for a much more comfortable long distance drive. And where I live it's pretty much a LONG distance to wherever I'm headed! 

 

For example, three Mini events I attended recently - KC to Wytheville, VA - 900 miles one way. KC to Aspen, Co - 816 miles one way, KC to Texas Hill country (San Antonio area) 950 miles one way. This and we'll probably drive 3-400 miles on the events too. Having the lower revs really helps keep my sanity on these long drives....especially when I went from a 3.44 to a 2.76.

[Johnmar]

I run 2.76 final drive in my cars and I don't find it to be doggy around town, the reduction in revs on the highway makes for a much more comfortable long distance drive. And where I live it's pretty much a LONG distance to wherever I'm headed!

For example, three Mini events I attended recently - KC to Wytheville, VA - 900 miles one way. KC to Aspen, Co - 816 miles one way, KC to Texas Hill country (San Antonio area) 950 miles one way. This and we'll probably drive 3-400 miles on the events too. Having the lower revs really helps keep my sanity on these long drives....especially when I went from a 3.44 to a 2.76.

Thank you Magneto.

I'm thinking the same. If they made a 998 with 2.95 FD, then I cannot see why a 1275 with 2.76 would be worse.

I don't need a screaming mini. I have had a van with a MG metro engine in it with a 3.44. It was fun but not for a daily commute.

Thank you for sharing your expereance. It seems we are thinking the same here.

Edited by Johnmar, 17 November 2021 - 07:59 PM.

[Cobra64]

Just wondering (hoping) if it is possible to change the crown & pinion without removing the engine/gearbox from the car?  I realise that the engine would need supporting off the ground so that the LHS engine mount can be removed.

 

Has anyone attempted/achieved it?

 

I've got a RE13 cam & lightened flywheel in a '98 Sportspack (2.76 FD) so it barely gets going from standing start.  I have to slip the clutch massively if starting off up a hill.  Looking to go to a 3.444 FD.

[Spider]

I can't say I've ever tried it with the engine in the car, it would be such a ball ache to try. If you have studs holding the diff cap on, then that's a no go, it will be engine out.

Given it only take around 20 - 30 minutes to remove the engine and say around 1 to 1-1/2 hours to refit, I've only ever don it that way, where I can see everything I need to and get at it.

[Ethel]

Theoretically it's supposed to be possible, but you'd need virtually everything disconnected that you would to lift the engine out anyway.

[Johnmar]

Theoretically it's supposed to be possible, but you'd need virtually everything disconnected that you would to lift the engine out anyway.

Oops,

Just read this message and the one from Spider. totally forgot to teel that the engine is already out of the car as the body it still in the rotisserie.


A lot of things has happend since my last post. Not all that pleasant.  Lets say that I'm looking forward to collect the keys of my small storage/work unit this month. Hopefully I'll be able to have everything fitted so I can use the unit this winter. 

Hopefully then I can restart my restoration..

[Cobra64]

I had a bit more of a look at it and seems like it'd be a knuckle-shredder so might pull the engine instead.  Then I can replace the flywheel and maybe clutch too with ease.

 

The diff cap is bolted on (no studs) but trying to shim & seal under the car off chassis stands could be difficult.

 

Thanks for your collective help...would still be interesting to know if anyones done it.