Berlina LSD install into Sprint GT

[Alex]

Last summer I decided to take my car off the road until I had diagnosed and fixed a nasty leak in my 4.56 differential. Other commitments prevented me from doing much about this until last week, when I had two days to remove the old diff (this is an ATE version which I had fitted to the car in early 2000 to replace the Dunlop unit, which I've still got) and install a 4.3 Berlina LSD which I removed from a car in the north of England early last year.

Not having the required tools or insider knowledge to rebuild the LSD myself, at the beginning of April I travelled up to Cumbria in the north of England, home to Cloverleaf Transmissions where Charlie Skinner is reckoned to be the best specialist Alfa transmissions rebuilder in the country, and almost certainly the only guy with all the correct factory tools - not to mention a huge stock of spares. After he used a little persuasion on me, Charlie re-used my original clutch plates in addition to a new pair of plates, building the stack of plates and shims to result in approximately 40-45% lock. Everything was totally stripped down and checked, and rebuilt to the closest possible tolerances. All seals and bearings were first-quality items from Alfaholics. The job would take about 6 hours, so I left him to it and returned later that day after a little tour around the lakes and hills of the area (I recommend it).

A while ago, I masked and shot blasted the axle tubes and had them powder-coated by a local company, then thoroughly cleaned them inside to remove all traces of grit that might chew up the fresh oil seals later. I decided to re-use the backing plates and handbrake mechanism from the old diff as I had restored these about three years ago and were still perfect.

So, taking advantage of a spell of warm, dry weather I topped up the old diff with oil and drove the car slowly from its winter storage to the garage at home. Jacked up the rear of the car (under the diff sump) and placed axle stands under the chassis points at the front of the trailing arms, then used small bottle jacks under the rear of the trailing arms to relieve the tension on the trailing arm bolts and allow everything to come apart smoothly. The handbrake mechanism was disconnected and tied off, likewise the flexible brake line from the MC, the rear calipers, dust shields etc, and used a rudimentary slide hammer to pull out the old shafts from the tubes. Once the propshaft coupling and trunnion arm were disconnected (watch out for the nose of the diff case rotating forward at this point) everything was carefully lowered on the jack and pulled free.

[Alex]

Luckily I've got the use of a 10-tonne press, so fitting the outer wheel bearings was a breeze. However, I made a slight mistake by omitting the ring spacer when pressing on the bearing for the first time and realised what had gone wrong when it was clear that the back of the wheel nut bolts were fouling the handbrake mechanism. Luckily it wasn't difficult to turn the shaft 180* and carefully press off the bearing. I didn't realise that the 'bell' at the end of the LSD axle shaft is of a slightly different shape and length than that of the standard shaft, hence the problem! Anyway, once that was corrected it all fitted together smoothly ...

Now for the fun part

Whereas the Sprint GT's outer rear wheel bearings were originally held in place by a threaded retaining ring (Dunlop diff), the later versions of shaft use a shrunk-on metal ring that fits on snugly behind the bearing. I doubted that the press was a good idea so out came the big propane gas torch and heated that ring up until it glowed red-hot. Working quickly, this was dropped down the shaft (make sure the 'step' is facing downwards) and then I dropped a length of heavy metal tubing immediately after it just to make sure it seated properly. Easy! Just let it cool for half an hour before doing anything else with it!

Now the halfshaft tubes had to be fitted up to the diff casing. The studs were cleaned up with a die and I made sure the sealing surfaces were totally clean and grease-free (I used thinners and then some 'pre-prep', I think its correct name is carbon tetrachloride but don't quote me on that - but you can also use acetone). I used Loctite 518 anaerobic flange sealant (don't use silicone if at all possible) and moly-coated M8 locking K-Nuts to clamp it all together - you don't want to use regular nylocs here as it gets too hot for them. Either that, or you clean up and re-use the original lockwashers (if they're not beyond recovery) and bend the tabs around the nuts after you've tightened them. There is a torque figure for these nuts, so check the workshop manual.

Apart from making new lengths of copper brake pipe, the tricky part was over. Reinstallation is just a reverse of the dismantling. Bled the brakes and hooked up the handbrake mechanism, adjusted that and bolted up the propshaft.

So eventually the wheels go back on and .... bugger! There's just a little lateral play in the outer wheel bearings. Not enough to worry about immediately, but in the next couple of weeks I'll have to remove the halfshafts once more and carefully shim these bearings with a purpose-made dense fibre ring just inside the opening to the half shaft tube, but at least this shouldn't take all that long.

I was pleased with the result. It's going to need running in and I'll change the oil after 500 miles just in case (I'm using Morris 90W LSD oil - but don't even try looking for that in the US!) (and another thing I noticed is that the filler plug uses a different Allen key to the earlier diff), but so far so good. It runs quiet and no perceptible lash (yet). Maybe soon I'll check out that limited-slip action too ...

Alex.

[Alex]

And here's the finished result.

[aikendrum105]

Wow

I'm leaning towards an LSD diff to replace the badly lashed one in my Duetto. Thanks for posting this info ! Really tidy install - mine usually come with free greasy fingerprints everywhere (just like the factory eh ? )

I'd been using that permatex aeronautic gasket stuff on the alloy casings (gbox etc) which seems to work ok, but that loctite flange sealer looks the business - might have to give it a go when I split the gearbox this month. (3rd synchro is balking)

Cheers !


Scott.

[conedriver]

Hi Alex,

A very pristine installation on what appears to be an exceptional car.

And... a good hint for use of permatex anerobic gasket sealer.

One question (with all respect): I always heard that use of brass tubing for brake lines was absolutely not recommended. Are those brake lines actually brass?

[Alex]

Hi George,

The brake lines at this point are metric copper. Although I've never checked this as they're covered in underbody sealer, the hard lines running under the chassis might be steel ... I stand to be corrected on this though. I also use Automec DOT-5 hygroscopic silicone brake fluid and (touch wood) I've never had any kind of seal failure nor any issues with sticking brakes owing to humidity absorption. Thanks for your kind words.

Alex.

[Subtle]

Good review--I'll soon have a lsd installed in my Spider.

[alfa2go]

Alex,
I am about to get a LSD diff rear end refurbed soon, and was looking at getting the parts from Alfaholics. Since I am in Oz I want to make sure I get all the parts I need first go. Is this what you ordered? :

1 x Diff pinion oil seal
1 x front and rear pinion bearings
1 x diff case bearing
2 x rear wheel bearing kits

Thanks

[AussieTony]

Alex I don't suppose you still have your old 4.56 gears? I've only just stumbled into this forum and am looking for some short gears for my diff. I will search and post elsewhere but what happened to the old CW&P?

Tony
Canberra AUS

[Alex]

Hi Tony,

I don't usually sell or throw away anything if possible. I've still got the Dunlop rear end and the ATE rear end (both 4.56:1) and they'll stay with the car just in case I ever decide to sell it one day. Ditto the Dunlop brakes and the original front axles.

I'm sorry I cannot help you, but there are plenty of people who have swapped out that ratio for something else, so I'd suggest posting in the 'Parts for Sale and Wanted' section. Good luck!

Alex.

[alfacorse1965]

Dear Alex ,and alfisti ,I am from Romania and I own a 69 gt junior with 1.6 engine.I have purchased from ebay a dismantled rear 2.0 GTV axle with LSD,and I dont have the rear bearing (large) from the pinion.My measurments indicate 35 mm inner ring,76 mm outer ring,and about 30 mm height.Unfortunately I'm not able to find one to match in my country so please if anyone can tell me the dimensions in inch ,or provide a clear photo,or best tell the manufacturer (SKF,FAG,Timken etc) and the code I will apreciate very much.Tks for your answer and interest.
Regards,
Serban

[Subtle]

As I recall, Alfar7 put Timkin bearings into the rebuild of my 2 L diff.

Maybe he will tune in, but he also machined 2.5 lbs off the ring gear.

[101/105guy]

A fine job !!
Did you have an issue with joining the late diff with the early drive shaft ?
I believe that the late models have larger bolts.
Randy