ford diff backlash adjustment

[pkw2704]

is this something that can be done with feel ,rather than dropping the diff off .or even adjust and run  to see if it quietens it down.or can the diff cover be removed insitu and adjusted?

[7 wonders of the world]

Whilst you can adjust the castellated collars in situ I would strongly recommend its taken out in order that you can check the unit correctly as the backlash on these is only a thou and isn't detectable by feel even with a thin coat of oil - they need to be clean and dry in order to e accurately measured.

neither can you look at the wear on the CWP or bearings.... these may well be the origin of you noise.

Alternatively pop the final drive out and send it to SPC in the non blatting part of the year and have it checked and rebuilt as required - maybe even add a Tracsport LSD whilst its out 

 

[David_Long]

Here's a video showing how the Ford manual recommends setting it up. The important thing is that the bearings are preloaded correctly, otherwise you are wasting your time at the case flexes under load. This was one of the issues with the Caterham supplied diffs around 2008 - they set the backlash without pre-load on the bearings.

 

[pkw2704]

understood guys and i wont mess,  just wondered if the diff cover could be removed in position on the car ,to have a look inside. the noise is annoying. though.......

[SM25T]

Have you checked, or maybe replaced, the oil ?

[Tom_Arundel]

Caterham diffs. are out of the airflow and get hot which significantly reduced the oil viscosity and that affects the noise.

All the pre-loads go out of the window as it gets hot.

The oil itself gets `mangled` when driven hard so it does pay to change it.

It is only 1ft. from your ear!

Carpet helps a bit!

I did adjust mine in situ. by trial and error and ended up 6 notches tighter, which is quite a lot but also quite a lot quieter!

There is also a possibility of metal to metal contact (spacer washers mostly) and there have been loose mounting bolts.  

`Unusual English engineering` is why we bought Caterhams...isn`t it? 

[BrettJ]

@David_Long, I don't suppose you have a similar video for the BMW diff?

[aerobod - near CYYC]

Re #7, this may be one of the most relevant BMW diff rebuild videos: https://www.youtube.com/embed/WSRgCX_LmOM?rel=0

We have a 168K (168mm) diff in our Caterhams that uses circlip shims that are available in thicknesses in increments of 0.02mm. You either need a shim kit or order a number of them around the sizes that are already in your diff. The size in mm is etched into the circlip face. Some people just buy oversized shims and have a machinist with a precision grinder reduce the thickness to whatever value you need. To check the shim size you need to remove the side seals and replace with new ones after the shims have been replaced. Backlash is typically around 0.1mm, but I've never seen a Caterham spec and BMW don't typically release rebuild info for diffs for current cars.

I would say removing the rear cover and cleaning oil off the gears before doing a backlash check would be a first step, if it is in the range of 0.05 to 0.15mm and the bearings are good, there is probably little point in rebuilding, unless the LSD is being rebuilt or replaced, too.

There is a bit more info in the tech guides from when I did my BMW/Titan diff rebuild the winter before last: https://www.caterhamlotus7.club/guides/maintenance/titan-limited-slip-unit-overhaul

[pkw2704]

mines  ford sierra 

[pkw2704]

So i decided to have a play with it  on the car. Marked the position of the castellated bearing adjusters,so i could go back to the  original settings  if needed,so after a little adjustment ,mainly to eliminate the play between the prop/pinion and the drive shafts.i took it for a blast and the difference is quite amazing,no drivetrain clunking on light throttle,the diff whine/noise is greatly reduced,and has me happier with the car( i think i may have just got lucky with the adjustment) ,so it stays for now,I will monitor it and see how it goes,but very happy,chalk and cheese ,could it get quieter as it beds in??

[7 wonders of the world]

the play you feel in the prop is not the true backlash.... there's running clearance in there for the differential gears... so you can't do this by feel on that basis.

You need to be very careful as you run the risk of running the CWP tight, overheating it which can then seize in operation resulting in a swift stage left exit...

...I saw the results of a Westy final drive that had been 'set' this way..... car needed some work to !

Straight forward job to take the final drive out and have it set correctly 

[ScottR400D]

#11 That would be my view with the obvious thought that if it were that easy CC would surely have got it right by now. Wouldn't they? 

[pkw2704]

i will drop it out and double check when i have the time,main thing is for me is its the diff area not g/box

[David_Long]

I think the reason Caterham, and their agents, had trouble getting the diff quiet was two fold. The worst examples relate to 'pattern' parts produced under license (and stamped with the Ford logo) that simply were not of the same design quality as the OE part. Secondly, the genuine Ford parts where not fitted as intended by Ford.

The Sierra diff was developed after quite a lot of R&D and this technology was closely guarded and limited to a small number of production lines. The contact patch pattern we see widely shared on YouTube videos is an engineering interpretation of what is correct - not necessarily wrong in an engineering perspective, but not what was used by Ford.  If you dig into the history and available archives, you see their production process used an offset pattern. This pattern dispersed the oil from between the teeth in way that reduced the whine.  But the 'non factory' techniques, although arguably correct, can override these subtle design features. 

The relevance to this thread is that adjusting the backlash to the extreme limits can reduce noise - the trick is balancing noise reduction against reliability and service life.