Lotus Elan

Hissing sound from diff

PostPost by: SENC » Tue Apr 03, 2018 10:23 am

JonB wrote:
SENC wrote:As I'm about to reinstall my diff after pinion seal replacement, I have some concerns I'll find a similar issue. To avoid getting there and having to disassemble the entire rear suspension again, would I have any risk in running the diff without wheel load to test for whining?


If you have doughnuts they will be highly stressed by running them with the suspension in full droop. Same for CV joints (even on a +2 you'll be working them hard). Also, the sound I got only occurred when the diff was under load. To recreate the load, you might try to apply the handbrake.

If you run it without the wheels connected you won't get any loading, so the results might not be indicative.


Thanks Jon. I was thinking of running it before connecting the cv drive shaft - though I did realize the lack of load might not give me a real test.
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PostPost by: rgh0 » Tue Apr 03, 2018 11:51 am

Thinking about it the lack of hissing when not loaded suggests the pinion bearings are to loose not to tight in my mind.

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PostPost by: JonB » Tue Apr 03, 2018 12:26 pm

OK Rohan.

Maybe I should try to loosen it a tiny bit first? If I tighten first and the crush tube is extra crushed I cannot uncrush it..

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PostPost by: rgh0 » Tue Apr 03, 2018 1:10 pm

Yes try both ways but loosen first like you say I think.
Look carefully at everything else you have changed in the rear end such as the diff mounts etc to see if they may be causing the noise

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PostPost by: Hawksfield » Tue Apr 03, 2018 5:44 pm

JonB

You say it was hissing when running, my experience with diff mal adjustment is a whine that can be noticed when either accelerating or decelerating and goes off with light throttle between both. Usually starting around 40 to 50 mph
Does your hiss start immediately ie minimum speed or higher.

Did you rotate the diff during finally tightening to ensure that the bearing cones were aligned properly
Is there any end play on the pinion at present, not easy to discern that would show it is under tightened

I am no expert just my experiences with diffs in cars owned by me and friends

Good luck hope it works out
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PostPost by: JonB » Tue Apr 03, 2018 6:57 pm

Good point John, I will check when I am next under the car.
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PostPost by: c.garde » Tue Apr 03, 2018 7:41 pm

Hi all,
A very precise description of my experience with a tired diff. output bearing.
Anyway a possibility.

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PostPost by: elansprint71 » Tue Apr 03, 2018 10:59 pm

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PostPost by: elanfan1 » Wed Apr 04, 2018 12:29 am

I suspect the reference to long gone members will be lost on many people here now. Countdown to moderation starts ..... Now.
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PostPost by: vincereynard » Wed Apr 04, 2018 12:34 am

Steve! What are you doing up this time in the morning - I'll tell mother!

Did you fit a new crush tube? They are not supposed to be reused. (It has already been crushed!) Get a new one, stick it in, torque it up, off you go.
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PostPost by: JonB » Wed Apr 04, 2018 6:03 am

HI Vince

When I asked about this I was advised that I could reuse it if I ensured the pinion nut was returned to its previous position (by virtue of counting the turns and lining up pre-made marks). According to what was said, I'd have to have the crown wheel out to do it right, if using a new crush tube.

lotus-gearbox-f37/pinion-oil-seal-t41056.html (second post).

I must have got the torque wrong.

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PostPost by: Hawksfield » Wed Apr 04, 2018 10:35 am

JonB

Did you actually torque it to a set lb./foot on the nut as the correct procedure is by turning torque of the pinion shaft without crown wheel as you tighten the flange nut.
I don't know why they have a torque setting in the manual as the Ford spec has no set torque for the flange nut
If you were to use this setting to replace a pinion seal it would compress the crush tube again upsetting the pinion shaft turning torque setting.

This is only my assumption of the actions of torqueing up on replacing a seal
Good luck in a resolution
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PostPost by: JonB » Wed Apr 04, 2018 1:21 pm

Well, this is useful:

http://www.skf.com/binary/30-285048/TT08_024.pdf

Whirring noise - points to loose pinion bearing preload. Other readings suggest the handbrake might be dragging (I did adjust it prior to this test run) and so I will loosen that off slightly first as it is easy to get at. Pretty sure it's the diff though...
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PostPost by: JonB » Wed Apr 04, 2018 1:24 pm

Hawksfield wrote:JonB

Did you actually torque it to a set lb./foot on the nut as the correct procedure is by turning torque of the pinion shaft without crown wheel as you tighten the flange nut.
I don't know why they have a torque setting in the manual as the Ford spec has no set torque for the flange nut
If you were to use this setting to replace a pinion seal it would compress the crush tube again upsetting the pinion shaft turning torque setting.

This is only my assumption of the actions of torqueing up on replacing a seal
Good luck in a resolution


Well, since the nut has a nylon locking ring you would have to apply some torque just to wind it onto the thread.. but as discussed, I followed Rohan's advice and reset the nut to the same place it was before disassembly. That said, I might be a turn out. I need to experiment with it to find out for sure.
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PostPost by: pharriso » Wed Apr 04, 2018 8:26 pm

JonB wrote:Well, this is useful:

http://www.skf.com/binary/30-285048/TT08_024.pdf

Whirring noise - points to loose pinion bearing preload. Other readings suggest the handbrake might be dragging (I did adjust it prior to this test run) and so I will loosen that off slightly first as it is easy to get at. Pretty sure it's the diff though...


Thx for posting, that will be useful.
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