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Differential Questions
#1
  This topic is about my 1979 Triumph Spitfire
ajohncock Alex Johncock
Salt Lake City, UT, USA   USA
Hi guys, first let me say that I did some searching in the forum and found some info, but not the specifics I am looking for.

I have a few question in regards to the differential in my car. It has a rather loud whine that only appears at high(ish) speed, about 40 mph and above. It's obnoxious, but doesn't seem to have any other ill effects. My questions are:

1. Are there any obvious and simple issue that could cause this? - I haven't checked fluid level yet, but will soon.

2. How long do they take to swap out, and how difficult is the job? Any special tools required? I've got a parts car I can pull one from, but I have no indication if that one is in any better shape.

3. Can I identify the ratio by any markings on the diff?

4. If I do end up swapping one from my parts car, are there any components I should replace while I've got it apart?

Thanks! Any other input or suggestions are more than welcome!



Edited 3 time(s). Last edit at 2017-12-30 09:15 PM by ajohncock.

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Doug in Vegas Avatar
Doug in Vegas Douglas D
Las Vegas, NV, USA   USA
Basic swap on a car this old is fairly easy if you can get it in the air. I would go all four points to the top of the stands. You have to drop the exhaust from the manifold. Then remove the rear half-shafts and drive shaft. This means the shocks and radius rods. Then there's the fun of getting inside the car and removing the access panel and pulling the spring studs. Now you can remove the front mounts and swing the diff down on it's rear bolt usually into one's chest. About now you notice the mounts could use new rubber.

grumpicus Steve Jackson
Leicester, Leicestershire, UK   GBR
A few answers:-

1. Whining from the diff is generally caused by wear in the bearings, allowing the crownwheel & pinion to move very slightly under load, so that engagement of the gear teeth is less than ideal. It's quite common for the noise to be worse at some speeds than others, I suspect it's some sort of resonance. I once had a diff that whined at around 37mph, went quiet above that speed, but got very noisy again at around 75mph. The late diffs (from about 1973 onwards) use the 'collapsible spacer' on the pinion shaft to set the initial pinion bearing preload - at best this idea is a compromise, at worst it's a disaster. (Earlier diffs used a solid spacer, which clamped the inner races of the two taper roller bearings firmly to the pinion shaft - the collapsible spacer doesn't do that once pinion bearings start to wear.)

2. Swapping the diff is as Doug outlines - just lets say it's easier with the body removed from the frame/chassis! winking smiley I've done both, and I'm getting too old to support a diff on my chest....

3. Markings on the diff don't help much, but all US spec Spit 1500s had a 3.89:1 ratio from the factory, and the diff serial number had a 'FH' prefix.

4. If the diff seals are leaking, it's a good idea to change them (especially the output shaft seals). The input shaft seal means that the nut has to be removed from the input shaft, destroying the pinion preload settings if a collapsible spacer is fitted. It's commonly stated that the nyloc nut has to go back in exactly the same position, to avoid changing the preload on the bearings by crushing the collapsible spacer even further. My experience is that once the diff has covered a few thousand miles, the bearings will have developed wear, and the collapsible spacer will no longer be doing its job very effectively, and the bearing preload will then be much less than when set at the factory.

Swapping the diff may result in a reduction of the noise - or a different noise entirely. As well as having the obnoxious collapsible spacer, all diffs from about 1973 onwards had fibre thrust washers behind the sun gears in the diff assembly. The idea was that these wretched washers would compress slightly during assembly, making it easier and quicker to assemble the units. Once in use, these thrust washers wear much faster than the old style brass or copper thrust washers, allowing backlash to develop between the sun & planet gears in the centre of the diff. This leads to all sorts of random banging/clonking noises from the unit, and can occur from a lowish mileage. As the BL warranty period back in the 1970s was only 12 months or 12,000 miles, the fibre washers probably failed shortly afterwards! There are also cases where the fibre washers have broken up completely, or were missed out during initial assembly.

FWIW, I'm currently rebuilding a late US spec 3.89:1 diff - with new bearings, copper thrust washers and the earlier 'solid spacer + shims' setup. Hopefully it will last more than 12 months/12,000 miles!

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tapkaJohnD Avatar
tapkaJohnD John Davies
Lancaster, Lancashire, UK   GBR
See the Canley Classic Technical Archive page on Rear End Noises: https://www.canleyclassics.com/technical-archive/rear-end-noises
Note the remark that "The differential gets blamed on all too many occasions" and consider the other possibilties.

JOhn

grumpicus Steve Jackson
Leicester, Leicestershire, UK   GBR
In reply to # 1505216 by tapkaJohnD See the Canley Classic Technical Archive page on Rear End Noises: https://www.canleyclassics.com/technical-archive/rear-end-noises
Note the remark that "The differential gets blamed on all too many occasions" and consider the other possibilties.

JOhn

Very true, but the OP was complaining about a whining noise that occurs at high speed. Even the Canley Classics archive page indicates that noise comes from the diff, although they blame the case hardening on the gears - I reckon that misalignment of the crownwheel & pinion can cause enough noise to induce panic, long before the case hardening fails!

skyking1231 Avatar
skyking1231 Silver Member Frank Strobel
Mt. Sinai, NY, USA   USA
1975 Triumph Spitfire 1500 "Lil' Rose"
if you do remove your diff....anger is your friend. mine was a battle to get out. (with everything removed....the diff was 'stuck' in the car....aggression, anger...even hatred eventually got it out). Now putting the new one in...was easy peasy eye rolling smiley

but the job is straight forward....you will need some sort of long rod...to knock or tap the hinge pin/bolt out on the back of diff

...I got a rebuilt one from BP.

ajohncock Alex Johncock
Salt Lake City, UT, USA   USA
Thanks for all the input guys! That's a lot more information than I had before. I'll do some more reading and then start working. Thanks again.

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tapkaJohnD Avatar
tapkaJohnD John Davies
Lancaster, Lancashire, UK   GBR
If you are determined to remove the diff, then dismantle the rear suspension .
Knock up a diff 'carrier' from scrap wood - it really won't balance on a jack, and is too heavy to lift by hand (IMHO) See below
And buy two bolts to replace the single long one - much easier to replace!

John


Attachments:
Diff carrier 4.jpg    56.2 KB
Diff carrier 4.jpg

mkivmarty Avatar
mkivmarty Marty Yanik
N.E.Ohio, USA   USA
In reply to # 1505183 by ajohncock 1 - I haven't checked fluid level yet, but will soon.

BEFORE you take all of the excellent advice above, put some oil in it. Much easier to do. It may solve your problem short term, and prevent any further damage from occurring.

Marty

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Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
In reply to # 1505242 by mkivmarty
In reply to # 1505183 by ajohncock 1 - I haven't checked fluid level yet, but will soon.

BEFORE you take all of the excellent advice above, put some oil in it. Much easier to do. It may solve your problem short term, and prevent any further damage from occurring.

Marty

Totally agree! and if the noise persists I would even tighten the pinion nut (just a little) to see if that makes any differance, before 'biting the bullet'and dropping the diff.

As for removing the diff, I have done this many a time with the axels in situ. Yes, they are in the way and need to be moved around a bit. If you do remove them, it would be a good opportunity to change the UJ's if you have any doubt about them.

Replacing the long rear bolt with two short ones is a good idea. As is making a saddle for the trolly jack.

mkivmarty Avatar
mkivmarty Marty Yanik
N.E.Ohio, USA   USA
[/quote]

.

As for removing the diff, I have done this many a time with the axels in situ. Yes, they are in the way and need to be moved around a bit. If you do remove them, it would be a good opportunity to change the UJ's if you have any doubt about them.

[/quote]

I remember the Wheeler Dealers episode where Edd used a ratchet strap over the trunk to hold the axles out of the way when he removed the diff.

Marty

trrdster Avatar
trrdster Wayne Tate
Spencer, NC, USA   USA
Alex and all, lots of us have struggled with and in most cases won ageist the heavy lump that turns the wheels. Some times the major problem has nothing to do with the rearend. The exhaust system, or back half of it needs to be gone, lots of places for the little Spitfire or GT6 to fight back. A couple of days before starting, put some penetrate on the brackets and pipe overlaps. While at it, give the rear long bolt, were it goes through the back a couple of shots. The bolt gets stuck in the collar of the bushing..
The trick is to not pry anything, that's where the excitement comes in, as things tend to move in a hurry when they weight this much.
A few folks have tried and removed and replaced leaving the spring in. Just not a good idea, all parts removed can be checked, if not cleaned.
Four bolts on the each out side for the suspension, slide those bolts back in their hole and put the nut and washer on. (top spring, bottom shock, trailing arm and trunnion). Now four each for on 3 drive shaft flanges. Quick way to get the axle ones is a 24 inch extension, u joint type 9/16 socket from the outside of the car, with the nut to be removed at the top. . bracing a openend against the frame. Air or a speed wrench makes quick work of it. The drive shaft bolts present them self at the bottom as you turn it..
All this should be removed before you attempt the studs at the top of the spring. Here's a little trick, that cross bolt in the cage that surrounds the spring, give it a couple of loosening turns, it allows it to move around slightly, not so much assistance on the taking out process, but you will thank me on the install, as the spring is locked in place by the slot and centering bolt, making it almost impossible to get the studs lined up. The spring will catch less on the rearend if you turn the spring sideways, curve towards the front.
If you were lucky, you now have all your fingers and not too many cuts. The prize is in sight. Take the nut off the cross bolt in the rear, now you will take a crow bar or such and pry the rear bracket apart just a little, it will help it come out of it's hole. The front nuts should be taken loose, down to a few threads, do not take them off, just get it down a bit, so the rubbers are loose. It doesn't seem right, but support the lump and take the back bolt out first, should knock out without a lot of effort. It will fall down when the weight is released a bit and now take the two nuts off the front. Being careful let the jack down to clear the studs and pull the jack forward to get the rear end out of the rear brackets. Don't let it wobble off to the side, a helper would be great at this time.
Install in reverse order, taking note to stuff the rear inside the brackets at the rear. Put the rubbers on the stud, top and bottom and install washer and a few turns on the nuts. All of this while supporting the rear with a jack. If you try and put the front on first and tighten it up, your nightmare has just begun, getting the rear inside the brackets. Use a couple of good size Philips head screwdrivers or small bushing pullers, the pointed bolt will go in easy, use a little anti seize on it.
I didn't say it was going to be easy, but really it is, just time consuming.
Have fun.



Wayne
1970 TR6
2000 Jaguar XK8
1949 Triumph Roadster 2000
1978 Spitfire (rust victim)
1971 GT6 (tarp covered for 12 years, rusted inside out)
1980 Spitfire (getting all the good GT6 parts, all poly suspension and Spax shocks)



Edited 3 time(s). Last edit at 2017-12-31 05:01 PM by trrdster.

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
When removing an old diff, I remove the studs. Sometime they come out anyway when you are un-bolting the spring.

Be aware. The stud holes go all the way into the diff case. Any muck that falls through the holes falls into the diff.

But as Wayne says. Make darn sure the noise really is the Diff! Many of us have been fooled!
Check and grease the wheel bearings, even the front wheel bearings. I have recently had a front bearng start to whine (drone) starting at 40 mph, at that speed it was difficult to tell where the noise was comming from. and yes, I did for a while suspect the diff.



Edited 1 time(s). Last edit at 2017-12-31 11:54 AM by Tonyfixit.

CraigL Avatar
CraigL Gold Member Craig Larsen
Santa Clara, CA, USA   USA
Thanks for all of the advise, everyone.

I am wondering if the high level of whine would be considered "normal" for speeds at 60MPH and higher. On I-5 in Calif. the speed limit is 70MPH and speeds at 75-80 are frequent. My '75 1500 has the stock diff and the Ford T-9 tranny conversion. At 80MPH, the engine is at about 3,500RPM. I don't really notice any whine until about 60-65MPH. Assuming the whine is from a primo differential, my questions are:

1. Are some diff oils better at reducing whine?
2. Are there any heat issues if I wrap the diff in sound deadening material such as Dynamat or other? Not sure how effective this would be, but would like to try. The sound may be propagated by the half-shafts, so wrapping the diff may not be so effective.

Thoughts?

Craig

brucejon Avatar
brucejon Bruce Jones
Santa Cruz, CA, USA   USA
1962 Triumph TR3B
1963 Triumph TR3B "Tupperware TR3"
1969 Triumph Spitfire MkIII
1972 Triumph TR6
I drive mine at 70 and don't hear it. I would investigate more.

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