So I bought 3.45 diff gears off the net and was given a LSD cone type center from a good friend. I've just bought another EL falcon (3.08 open diff), only 106000 on the clock. Immaculate! Anyway, pulled out the diff, stripped it down and installed the 3.45 gears, replaced all bearings, seals and crush washer, set the pinion preload to spec and then dropped in the center tightened it down and then found the diff wouldnt move at all, determined the pinion was too high in the housing.

After hours of research I found a thread that mentions the following:
3.08 diffs use a r75 housing.
3.45 diffs use a r78 housing.

The difference is the pinion depth. I have read on another thread that you can machine the bearing race in order to get the pinion sitting further away from the crown wheel.

What I Need to know is, what is the base line for the machining, eg. 20thou 40thou? I cant find anywhere what the actual difference is in the depth of the housings, I've spent hours. I figured as my first topic and post I would do a diff build thread and show all my findings to help anyone else out in the future.

Reference:
gearbox-suspension-brake-driveline-f4/diff-housing-differences-and-3-08-3-27-3-45-gears-t18113.html

From what I know 3.08 housing is too small for 3.45 gears. Might be easier just to sell the 3.08 housing off and get the proper 3.45 housing? Otherwise have a crack at machining it.

Yeah, after 2 weeks of trail and error, going to machine 1.1mm off underside of pinion so that bearing can press further on, get it back on Wednesday and will post final results including a tooth contact pattern and shims used.

Yeah, may've been less complicated using a 3.23:1 housing - plenty of those around. I replaced the carrier and pinion bearings on a 3.27:1 a*** - fit into a 3.23:1 housing no probs - same shims(a*** ones that is).
Some good info here http://www.thirdgen.org/techboard/faq-b ... about.html .
Check out your centre as well http://www.9bolt.com/technical.html .

Fit your crownwheel/bearings/shims and do that preload check first - then you can remove it and fit the pinion and do it, then leave it in. A set of digital luggage scales work well.

Best of luck with it all - it's not that hard as people make out - just time consuming.

Thanks Snap, I realised pretty quick it would of been easier to fit it to a 3.23 housing, but have 2 EL Falcon's, and a nice workshop, so can afford to have 1 on stands waiting for the upgraded rebuild.
At least at the end of it all I'll learn heaps, and make it easier for other people looking to do the same as I have.

Yes, it'd be nice to have some of those specific tools (dummy pinion for location depth), but you can improvise.

Well the good news is I've managed to get this working. For anyone that is thinking about doing something like this, I wouldn't attempt it unless you have patience and lots of different shims!

In order to get the pinion depth right, I have machined approx. 1.2mm from the underside of the pinion (so the bearing would slide further up the shaft rather then trying to machine the bearing race,) which was absolutely perfect (didn't even have to shim bearing race!), set the preload on the bearings (all new bearings) and then removed the pinion once more and machined up a solid spacer matching what the crush washer had crushed to.

In order to get my crownwheel in the correct position I stripped 6 old diffs to get the side carrier shims out. Trial and error and checking tooth contact pattern I found the perfect combination that gave me a nice preload on the bearings and also a nice tooth contact pattern.

I have also machined the lsd cones to prevent them bottoming out in the housing, added extra shims to ensure it was nice and tight.

This diff drives absolutely beautiful, perfect amount of backlash, perfect pinion preload, perfect tooth contact pattern. All up I spent about 10 - 12 hours setting it all up including machining parts.

I hope that this thread can help someone else trying to do the same thing as I spent hours researching and couldn't find any information and people were saying it couldn't be done.

Special thanks to Ryan Maisey for donating a lsd center to the cause, and Aaron Deary for helping machine the pinion and solid spacer. Thanks alot fellaz.

Nice work bngoold! Patience does pay off. Got any photos?

Coast side tooth contact


Drive side tooth contact


The closest car is my new 1 that has the diff from this thread in it, the other 1 is my old car which I am regrettably selling.

Unfortunately I didn't take any more photos during construction, my hands were always too dirty to pick up my phone lol. I just got the important ones. Hope this helps.