omega 24 v6
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| posted on 5/4/05 at 12:05 PM |
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Live axle diff rebuilds
Hi lads ive been reuilding race diffs for hotrod and f2 cars for a while now with no probs trouble is they are bed for breaking shafts, and as a rule
dont run up a lot of miles between ratio changes or rebuilds.
I have a dial gauge etc for setting the clearances (backlash)and none of my rebuilds have ever failed YET. Does anyone have data on bearing preloads
or pinion nut torque settings with a new crush tube so that i can rebuild for road cars in the knowledge that higher mileages should not be a problem.
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clbarclay
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| posted on 5/4/05 at 12:10 PM |
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Most of what you need to know can be found in a haynes manual etc.
Haynes mk2 escort manual gives all the above info for english and salisbury live axles.
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NS Dev
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| posted on 5/4/05 at 12:13 PM |
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For what axle?
I think if you have done a few before you will be fine. As long as you check the backlash and blue up the gears to check the mesh pattern then all
will be ok.
I thought the pinion turning torques were in Haynes manuals, but if not, I have the ford rally prep book at home and can give you the figure for
English or Atlas axles later when I get home.
I just made a torque arm (posh name for some strip with a couple of holes for 2 bolts to go into the prop flange!) worked out the centre of mass of
the arm itself then welded an appropriate lump of steel the the end the get the right torque application (too little for most torque wrenches!). I
just hold the bar at just above 3 oclock/9 oclock and let it go. The nut needs to be just tight enough that the bar sinks slowly downwards.
Will post the turning torque later!
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britishtrident
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| posted on 5/4/05 at 12:35 PM |
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Always judged the crush washer preload by hand rather than use a spring balance -- if you can turn it by hand with a fairly light grip on the flange
it is OK ---- seem to rember book figure something like 12ft/lbs but someone will look up the correct figure.
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omega 24 v6
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| posted on 5/4/05 at 12:38 PM |
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cheers lads any info will be fine. I'll double check my old haynes manuals. The thing i could not find was any preload settings for the
crownwheel bearings. If there are any do you know if the bearing caps should be at thier torque settings first or only after the preloads are set. I
hope you understand what i mean as there is bound to be a considerable difference either way round.Sorry i should have said its an english axle.
[Edited on 5/4/05 by omega 24 v6]
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NS Dev
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| posted on 5/4/05 at 07:20 PM |
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Right, just checked for you on the stuff I can answer!
For Atlas/Capri (Salibury) axles, or English axles, with a new oil seal the turning torque for the pinion should be 1.8 to 2.0 lbft +/- 0.2lbft
The diff carrier "spread" (preload) for the English axle, according to the Boreham escort prep book, should be 0.2 to 0.25mm with new
bearings.
Hope this helps,
Nat.
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omega 24 v6
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| posted on 5/4/05 at 09:38 PM |
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I don't fully understand the spread figure. Do you mean clearance from side to side. If so this this is about 10thou added to the backlash of 4
to 6 thou.This leads me to think i've got the wrong end of the stick so what is the measurement and where do i measure it at.
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NS Dev
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| posted on 6/4/05 at 07:25 AM |
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To be honest I don't either! I'm just quoting the "Boreham Bible"!!! (Ford Works Escort prep book)
I have never rebuilt an english diff, from the salisbury/Atlas point of view I assumed it meant that the casing was 0.2mm wider when the diff was
fitted into it's bearings (you have to spread the casing slightly to get the diff in on these) and this stretch on the casing was the preload
for the carrier bearings??????
I guess the English could be the same except that you spread the carrier using the adjuster rings. In other words I had assumed it meant that if you
measure the diff housing width empty, then install the diff and wind in the adjuster rings (doing all the centring and meshing at the same time) once
all is set, the housing should be 0.2mm wider. If it's not, but the mesh is ok, then you adjust both rings equally to get the housing stretch
correct?
This is all my interpretation though!
[Edited on 6/4/05 by NS Dev]
[Edited on 6/4/05 by NS Dev]
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omega 24 v6
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| posted on 6/4/05 at 01:05 PM |
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cheers ns dev i see what youre getting at there. seems like a difficult thing to accurately measure so i'll stick with the "it feels ok
method" but thanks everyone for all the info. This forums an ocean of knowledge
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madman280
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| posted on 6/4/05 at 11:30 PM |
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I don't know the specifications for the diff you're using, but below should give you an idea of what your looking for. I'm a
Technician at a Ford dealer and regularly work on diffs. Been doing it for 20 years or so. Apoligies if some of this is old hat for some, but for the
benifit of anyone else who may be interested, here goes.
Normally if the gearset doesn't have too many miles or any abnormal noise I'd re-use them. If you're just replacing seals and
bearings and no abnormal noises were present. I'd re-use the originally pinion depth shim. Pinion depth is how far the pinion engages into the
ring gear. It remains the same with the original gear set and original case, but if anything is changed it needs to be re-set. A bit beyond this
proceedure.
The amount of force that's required to rotate the pinion flange is the pinion preload. Its measured with a spring scale(like for wieghing fish)
and a short bar and a bit of math or with a dial type torque wrench on the pinion nut. The pinion preload is generally between 8 inch pounds and 16
inch pounds. (2 ft lbs is way too much thats 24 inch pounds. a bit much for the small diffs we would use) It's measured with just the pinion,
bearings, seal, flange and nut installed. Not the ring gear. All measurements are made with the bearings lubricated in new clean oil. If you need more
preload tighten the pinion nut. If you go too far, pull it apart and get another collapsable spacer. They don't stetch or spring back, once
they're crushed thats it. I always use a new collapsable spacer. They are only a few dollars so why risk ruining the cost of everything else you
just done over a dollar or two. Some diffs use shims instead of a collapsable spacer, but the same thing applies, add or subtract shims until you get
the correct preload.
To explain carrier bearing preload. A certain amount of shims will just eliminate any play. The specified preload is the extra amount or thickness
of shim that will need to be added beyond that. If threaded adjusters are used then they are generally torqued to a certain amount- I recall something
in the order of 60 foot pounds for larger diffs. Its not a bad idea to keep track of what was originally there as its usually not too far off.
Now the total gear back lash is adjusted by taking shims from one side and adding them to the other. Always keeping the same total thickness. The
back lash is measured with a dial indicator on a ring gear tooth. Its gernerally in the range of 0.008 inch to 0.016 inch Larger gearsets are usually
in the higher range smaller in the lower. You need this play or distance between the gears to allow for heat expansion and to give the gears a bit of
room to move against each other. No need to get too picky yet as this may be re-adjusted in the next step. You just try to get it some where in the
middle of the specs. Then a paste like marking compound is painted on the ring gear teeth. It can be anything that'll stick but can be wiped or
rubbed of by the gear teeth. The real stuff is lead based so be careful. I've used chalk, blueing while its still wet, and crayon. It sometimes
pays to be inventive here. Rotate the gears against each other and apply a bit of force. Your looking at the convex drive side of the ring gear. What
gets wiped off is the point the gears are sliding against each other. The aim is to have the area of contact in the center of the gear and the back
lash within the specified range. Dependant on the pattern it may be necesary to adjust the pinion depth. I usually aim to be in the low side of the
specs to allow for wwear.The correct setting of pinion depth is quite a bit more involved as is reading the contact patterns and knowing what to
adjust. It wouldn't be harmfull to make an adjustment the wrong way if things are done in small amounts. Just keep track of where you started
in case you have to go the other way. Hope that helps. If anything's not clear or you have any questions just ask.
[Edited on 6/4/05 by madman280]
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madman280
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| posted on 6/4/05 at 11:32 PM |
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Just wanted to add that the back lash is measured with everything assembled. the carrier bearing caps are fully torqued to specs. Its kind of a
progresion through the steps I oulined. One part builds on the other. Add some more parts and make some more measurements.
I've had to redo quite a few of the it feels right kind of measurements done by others. If you don't have much invested and don't
expect much its fine, but if your investing time and money, it pays to do it right the first time. Unless you want the practice
[Edited on 6/4/05 by madman280]
[Edited on 6/4/05 by madman280]
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NS Dev
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| posted on 7/4/05 at 07:17 AM |
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quote:
Originally posted by madman280
I don't know the specifications for the diff you're using, but below should give you an idea of what your looking for. I'm a
Technician at a Ford dealer and regularly work on diffs. Been doing it for 20 years or so. Apoligies if some of this is old hat for some, but for the
benifit of anyone else who may be interested, here goes.
Normally if the gearset doesn't have too many miles or any abnormal noise I'd re-use them. If you're just replacing seals and
bearings and no abnormal noises were present. I'd re-use the originally pinion depth shim. Pinion depth is how far the pinion engages into the
ring gear. It remains the same with the original gear set and original case, but if anything is changed it needs to be re-set. A bit beyond this
proceedure.
The amount of force that's required to rotate the pinion flange is the pinion preload. Its measured with a spring scale(like for wieghing fish)
and a short bar and a bit of math or with a dial type torque wrench on the pinion nut. The pinion preload is generally between 8 inch pounds and 16
inch pounds. (2 ft lbs is way too much thats 24 inch pounds. a bit much for the small diffs we would use) It's measured with just the pinion,
bearings, seal, flange and nut installed.
[Edited on 6/4/05 by madman280]
Maybe, but the 2 ftlb figure was from a Ford datasheet for just what you describe assembled!
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omega 24 v6
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| posted on 7/4/05 at 08:41 AM |
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Wow madman i'm impressed and concerned that none of the diffs i have ever built have had shims to allow the pinion to gear depth adjusted. This
would explain why one i particular kept sharpening the pinion gears to a razor edge probable no enough depth of mesh eh? thanks for the major
explanation it helps a lot. Like i said plenty info on this forum.
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madman280
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| posted on 7/4/05 at 06:43 PM |
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Quote:
writen by NS Dev:
Maybe, but the 2 ftlb figure was from a Ford datasheet for just what you describe assembled!
Quite possibly, seems to be in about the right range might even be higher. I'd think that would be the total assembly rotating torque
specification, not the pinion preload rotating torque.
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