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MG Midget and Sprite Technical - expert help needed! (mkIII diff)

Hi all,
I have a problem with the diff. After the installation of new Ivor Searle 1275 engine last summer I managed to set the SU's and timing and driving become the joy again (new engine is just GREAT).
Few weeks ago, during regular 2 years change of oil and change of the plugs in the diff I found out some oil sprayed all over the front part of the diff where the drive shaft is comming into it, so I suppose I have some leaks in there and the drive shaft - as it rotates - sprayes the road and car with the oil. The diff is working OK, no strange noises, it still hold some oil.

It is a standard diff for MKIII 1973 (as far as I know, because it is the last part of the the car I didn't need to open untill now in last 7 years of my ownership).

Can you please tell me which parts should I change to stop the leaking? I would like to avoid buying of needless parts. Ideally based on the Moss catalogue here, please:

http://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=29295

Thanks in advance!
Stepan
Stepan Marek

sounds to me like the normal rear crank leak from your 1275 and the oil is getting blown down the tranmission tunnel and coating your diff. Either that or you could have a leaking pinnion seal - again not a major problem. Both are covered in the archives at length.
Nick

28 120-800 $3.10
OIL SEAL

1: Take the bolts off the driveshaft and lift out of the way

2: use a big socket on the nut you uncover on the diff - an impact wrench is the tool for this job, but the handbreak and a breaker bar may work

3: slide the washer and flange off the splined shaft

4: leaver out the old seal

5: grease and press in the new seal

6: do up the nut and bolts
Will Munns

Nick, based on from where the oil seems to be leaking and on fact, that engine oil level is stable for last 1000 miles I think Will is right (thanks Will), but I will also check that.
Thanks for help, Stepan
Stepan Marek

Stepan,

Check the archives as I think Will has missed an important step. The pinion shaft has a crushable preload spacer which is no longer available IIRC so you need to note the position of the nut before removal so you can place it back in the same orientation, otherwise you need to do the pinion nut up until the torque required to rotate the pinion is at a specified value.
David Billington

The collapsible spacer (BTA532) is now available again :-)
However, it is not necessary to replace it when replacing the seal. The official workshop manual (for the MGB - the midget one covers only the solid spacer type) descirbes the procedure as
Measure the torque required to rotate the pinion prior to removal.
Then after assembly:
- tighten the nut gradually until resistance is felt
- rotate pinion to settle bearings
- measure torque require to rotate pinion. If less than pre-dismantling figure, tighten a very small amount then settle bearings & remeasure.
- Repeat until reaching a tourque which is the higher of either the pre-dismantling figure OR 4 to 6 lb-in.

It carries a warning that torque build-up is rapid, and if an original torque higher than 6 in-ilb (0.7 kg-m) is exceeded, the collapsible spacer must be renewed and the whole process repeated.
Paul Walbran

Thanks to all of you, I will order the oil seal and as it arrives, will try to change it.
S.
Stepan Marek

This thread was discussed between 30/06/2008 and 02/07/2008

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.