Running In New Diff

[Stuart+2]

I now have a brand new crown wheel and pinion and everything else following an output shaft failure many weeks ago.
I received only vague instructions on the correct running in procedure, ie vary speed then change the oil after one month.
I would welcome any advice on running in the new diff.
Thanks.

[mikealdren]

Hi Stuart,
I've never come across a manufacturer of any car who recommends running in and changing the oil in a diff. You may want to treat it gently for a short period but really it shouldn't be necessary.

Mike

[vernon.taylor]

Salut

Leslie from this forum has a lot of experience with diffs. I bought a 3.54 from him and he recommended to accelerate easy, stay below 3000rpm and change the oil after 500 miles.

@+

Vernon

[ardee_selby]

Just spotted that early Lotus manuals included:

Do we know what type / grade was used? Seems it could be mixed without problem whatever it was.

Cheers - Richard

[mikealdren]

Hi Vernon,
I agree about the gentle acceleration but revs are irrelevant, it's speed that matters for the diff because it's downstream of the gearbox.

WRT to running in: with modern oil, I still question whether an oil change is required. Does anyone have the original Elan user manual to see what Lotus recommended?

regards
Mike

[rgh0]

I would run in the correct spec but lowest cost mineral based hypoid diff oil I could find for 500km and driveg with care and with varying speeds to avoid overheating as the diff bedded in as recommended.

There used to be special diff running in oils avialable that had extra additives compared to the standard oils to help with the running in period but the additives in the standard diff oils these days are all you need for running in and no one seems to make diff running in oils any more from what i can find

After 500 km I would then change the oil and put in the best quality synthetic oil to the correct specification i could find.

Doing the change cleans out any metal particles that have come off and into the oil during the run in period as the gears wear into perfect contact

cheers
Rohan

[fatboyoz]

Stuart,
From my '68 S4 Owner's Handbook:

'Rear Axle,
The rear axle, when new, is filled with a special "running-in" oil. The used lubricant must be drained, and the differential housing flushed out (with a good quality flushing oil, not parafin (what we call kerosene)) at 500 miles (800km) and subsequently every 12,000 miles (20,000km). Refill the axle with the specified lubricant, after ensuring that all flushing oil is removed.'
Read Rohan's post above.
I use Redline synthetic 75W90 High Performance Gear Oil.
Read this article on flushing.
http://www.amsoil.com/techservicesbulle ... 0Flush.pdf
Would be expensive using the Redline as a flushing oil, but would definitely give you peace of mind that you have given the diff' a good start.
Regards,
Colin.

I now have a brand new crown wheel and pinion and everything else following an output shaft failure many weeks ago.
I received only vague instructions on the correct running in procedure, ie vary speed then change the oil after one month.
I would welcome any advice on running in the new diff.
Thanks.

[vernon.taylor]

Salut Colin

Wouldn't a cheap synthetic do as the flushing oil? As there is no load (I suppose back wheels jacked up?) perhaps the cheapest would be OK - it just has to last 15 minutes.

@+

Vernon

[fatboyoz]

Vernon,
Je suis d'accord.
Regards,
Colin.

Salut Colin

Wouldn't a cheap synthetic do as the flushing oil? As there is no load (I suppose back wheels jacked up?) perhaps the cheapest would be OK - it just has to last 15 minutes.

@+

Vernon

[msd1107]

"Running in" is to compensate for the method of machining that leaves micro-meter proud points of metal that are worn down and incorporated in the oil during the running in period. That is why there is special break in oil and why you change the oil after 500 (km/miles) of usage.

The differential has the greatest friction losses of any single item. REM super finishing will smooth out all the machining imperfections and decrease the coefficient of friction by at least a factor of two. There are now numerous licensed REM shops who will process your CWP for a rather nominal fee, especially attractive if you have disassembled your differential.

See http://www.remchem.com/.

A later and more expensive process is rf85 "http://www.rf85.com/". This purportedly reduces friction by 85% and usually obviates the need for an oil cooler in competition.

David
1968 36/7988

[Stuart+2]

Thanks to all for your valued advice.
I'll run it in and change the oil. Easier now, as I have just fitted the later diff casing with a drain plug (former casing was terminated by the output shaft).
Cheers.