Lotus Elan

Diff Unit Leaking Oil

PostPost by: CG901 » Thu Dec 05, 2013 8:57 pm

This is not an uncommon problem, but want some advice on what to do when I get it out and on the bench. This car (26/4004) has had no major service done since it was sold new in 1965. It has 84k miles on the clock and that is reasonably accurate based on the known history. Was planning to replace input shaft oil seal, two output shaft oil seals, and diff housing gasket. What about replacing the bearings? (pinion, output shafts, prop shaft)
I have a workshop manual and the Buckland book. What are the potential issues with taking on this task? Thanks
Current: 1965 S1.5 26/4004, 1966 S3 FHC 36/5192, 1958 Fiat Abarth 750GT Zagato, 1967 Brabham BT21B, 1988 Arrows A10B-04, 1991 Brun C91-001.
Past: 1971 Elan S4/SE DHC, 1972 Europa Special, 1980 Esprit Turbo, 1988 March 881-05, 1990 Leyton House CG90105
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PostPost by: PeterK » Fri Dec 06, 2013 8:29 am

Output bearings are cheap, so I would alway replace those while doing the seals.
Remember to remove the circlips before trying to remove the bearings. A slide hammer is your friend to encourage the bearings out. Use a Locktite type of bearing lock when fitting the new bearings.

My car is not yet running (doing a nut and bolt restoration of a completely disassembled, unfinished project that I bought in a moment of madness :-)), so pinion bering condition unknown. However, to avoid having to set the diff backlash, I just did the Wheeler Dealer 'mark the pinion nut, remove, replace seal and replace nut to original mark' and I hope that the pinion bearing is OK.

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PostPost by: RichardHawkins » Fri Dec 06, 2013 10:32 pm

You have the manual, so will see there are special tools required.

In my case the first problem was removing the circlips that were severely corroded, I was concerned I would break sections of the casing as I had with the rear hubs. I eventually got them out with patience and penetrating oil. I used stainless circlips when rebuilding. Carefully scrape away any corrosion of the aluminium casing on the outside of the bearing before using the slide hammer.

If I remember correctly there is a shim/spacer between the pinion and the bearing nearest the pinion on the pinion shaft. This is to set the depth of engagement with the crown wheel. If you are only changing bearings this shim should be correct as bearings are extremely precisely made and for most intents and purposes will be identical.

The pinion shaft bearings are pre-loaded. This preload is determined by the resistance to rotation of the pinion shaft whilst the pinion shaft nut is being tightened. There is a crush sleeve between the two pinion shaft bearings, the purpose of which I cannot remember, (I think it is to keep the bearings apart) but it should be replaced when changing the bearings.

There is a special tool to measure the pinion shaft resistance to rotation. I think Bucklands book shows it. I improvised by making a drum like a fishing reel, which I attached to the pinion shaft flange, wrapped cord round the drum and hung a weight on the cord.

Hope this helps,

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PostPost by: CG901 » Fri Dec 06, 2013 11:05 pm

Thanks to both Peter and Richard for very helpful comments.
Current: 1965 S1.5 26/4004, 1966 S3 FHC 36/5192, 1958 Fiat Abarth 750GT Zagato, 1967 Brabham BT21B, 1988 Arrows A10B-04, 1991 Brun C91-001.
Past: 1971 Elan S4/SE DHC, 1972 Europa Special, 1980 Esprit Turbo, 1988 March 881-05, 1990 Leyton House CG90105
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PostPost by: KevJ+2 » Sat Dec 07, 2013 12:48 pm

To add to Peter and Richard's comments, I found the use of heat when removing the drive shafts a great help (after removing the circlips of course!). I was advised to change all the bearings and seals whilst dismantled as although they seemed alright (to me anyway) they had signs of pitting. As this is not a job you want to repeat in a hurry, I would bite the bullet and do it all.
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PostPost by: miked » Mon Dec 09, 2013 8:58 am

Ditto on the heat otherwise you will not melt the loctite. A piece of a circlip is useful to clean the grooves when you have it all apart. Mike :)
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