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Daimler 15 rear differential/worm

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bop
Posts: 119
Joined: Mon Feb 15, 2016 3:26 am
Location: Alberta Canada

Daimler 15 rear differential/worm

Post by bop »

As part of the restoration of my car, I decided to change the oil in rear axle for the first time in at least 42 years (has been in storage awaiting restoration).
First question: is this a Type 3 differential?
1.JPG
4.JPG
The oil was more like tar
2.JPG
so I thought maybe this thick tar like stuff was put in to quiet the rear end and decided to check backlash
3.JPG
I must apologize because I didn't realize I went the wrong direction when measuring until I looked at photo later. It should read 0.041" (in small print on dial).

This leads to question #2: what is the correct backlash specifications?

And the last question: How is the backlash adjusted?

I would prefer to understand the correct way of doing it, rather then taking it apart and trying to re-engineer it! :D

thanks Bob

qantasqf1
Posts: 187
Joined: Mon Mar 07, 2016 10:13 pm

Re: Daimler 15 rear differential/worm

Post by qantasqf1 »

Bob, I can’t answer question 1, but I may be able to help on 2 and 3. I’m almost certain the backlash can’t be adjusted because there’s no provision to radially alter the position of the worm or the worm wheel. The only adjustment is setting the end float of the worm shaft by adding or removing shims from the front ball bearing, so if your worm shaft ball bearing isn’t being replaced it’s safe to use the original shim(s). The position of the worm wheel is altered by the diff carrier bearings’ shims because they set its central location relative to the worm, Again, if none of the parts is being replaced the original shims can be refitted. However, since there seems to be little information anywhere on this issue I’d be interested to find out more. I read somewhere the worm wheel should be offset by 0.002” from the central position towards the offside of the car, but I’m damned if I can remember where I read it. Sorry!
Steve

bop
Posts: 119
Joined: Mon Feb 15, 2016 3:26 am
Location: Alberta Canada

Re: Daimler 15 rear differential/worm

Post by bop »

Thanks for the reply Steve! If there is no backlash adjustment then that might explain why the only info I could find was basically for changing parts and the bottom line was "assemble it the same way as you took it apart". I don't know how one could find the central position accurate enough to then allow the 0.002" for the worm wheel offset :shock: I will still try to find more info on the differential and will let you know if I find anything.
Bob

qantasqf1
Posts: 187
Joined: Mon Mar 07, 2016 10:13 pm

Re: Daimler 15 rear differential/worm

Post by qantasqf1 »

That’s a good point, Bob, and I don’t have an answer to centralising the worm wheel. Maybe Daimler used a special jig. However, since posting my previous a faint memory stirred! As I recall, the worm wheel shim on the offside of the diff carrier is a standard (fixed) dimension, and the shim(s) on the near side are altered accordingly to achieve the required end float of 0.002”. If so, then the offside shim must be quarantined until it gets refitted in the same location. However, if the offside bearing is replaced then presumably its shim thickness would have to be recalculated by comparing the width of the old bearing and the new and increasing or decreasing the shim thickness accordingly.

Stan Thomas
Posts: 664
Joined: Sat Feb 13, 2016 2:14 pm
Location: Penkridge. Staffs.

Re: Daimler 15 rear differential/worm

Post by Stan Thomas »

The simple answer is that unless it is absolutely imperative to disturb the "adjustment" (i.e. by dismantling) NEVER NEVER try to alter the settings. If there is some wear, it is still far better to live with it as any alteration will enhance the possiblity of whine, and only lead to more rapid wear as there will be excessive pressure-point loading on the new contact areas.

I suggest you raise the axle off the ground, drain off the existing "tar" (*), refill and run the axle off-load with paraffin or white spirit for a few minutes, alternating between chocking each wheel in turn to activate the differential gears. Do this a couple of times to completely flush out, then let everything dry off and refill with Silkolene Rhino 140 Classic - which is especially blended for bronze wheel worm drives.

Do all that first and road test before you attack the axle with spanners if you must.

If you really want to improve things however, change over to a modern lip seal on the worm shaft whilst you have the axle drained - details are on the 'net at:



(*) - "tar" - a brummie expression for "Thank-you".

bop
Posts: 119
Joined: Mon Feb 15, 2016 3:26 am
Location: Alberta Canada

Re: Daimler 15 rear differential/worm

Post by bop »

Thanks for the info Stan. I have already washed the differential with paraffin and filled it with Mystik JT-7 Gear Lubricant, 85W140. (quote: Mystik JT-7 Multi-Purpose Gear Lubricants, in addition to meeting API GL-6, meets the requirements of the API MT-1 Classification for non-synchronized manual transmissions. The MT-1 Classification has a requirement for compatibility with yellow metal parts, therefore, gear oils which also meet MT-1 will not cause a problem with corrosion of yellow metal within your non-synchronized transmission or gear box.) On your advice I checked for a Silkolene dealer in Canada but there are none.
I did not get a chance to do a test drive as the weather turned and we now have 4" of snow and daily high temperatures of around -9C. I am afraid I will have to wait until spring before the test drive happens. My main concern is trying to prevent any needless wear on the gears. I would hate to find out years down the road if only I had......
Oh well it is not like there is nothing else to do on the car!
As for the video, thanks, I did stumble across it already in my search for info.
"tar"
Bob

Culbu
Posts: 252
Joined: Tue Nov 15, 2016 5:21 pm
Location: Deauville, FRANCE

Re: Daimler 15 rear differential/worm

Post by Culbu »

Interesting video. Does anyone know the exact dimensions of the modern spi joint shown ?

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