differntial bearing housing

[bex1151]

In the process of refurbishing my differential, I have discovered that the differential was previously rebuilt without any half-shaft Bearing Housing dowel pins .  In fact it appears that the Housings have been replaced in that the pin holes in the Housings do not align with the holes in the differential casing.  How big of a problem do I have?  Can I rebuild without the dowel pins?  Do I have to fabricate new bearing housings?  If so, do I need to line bore both bearing housings?  Any guidance would be appreciated.

[Robin A Woolmer]

Gerry  Hawkridge of Hawk Cars is due to make new bearing housings for the Ace differential housing, so they should allow you to re-fit the dowels.
   It would be very difficult to line bore the Differential housing ,these are fabricated & welded into the Ace chassis, the main issue is to get the bearing housings in line with the differential assembly so the splines are in line with the housing.
   Be aware that the Aceca Bearing housing is slightly different
   Gerry should be able to help you.
   
   Robin

[Klassik Metall]

On the Ace units I've seen the dowel pins are welded on the ends inside the diff housing. I've rebuilt Ace & Aceca differentials & am not aware of any differences in the bearing housings, indeed I have interchanged them between the two models.
   
   I've also fitted new billet CNC machined bearing housings from INRacing in Nottingham, (part No. ENG1301) without any alignment issues.
   
   I would go ahead & refit the dowels in their original holes together with a pair of new housings. BTW the original dowels should be 3/16" diameter.
   
   Regards Luke

[Robin A Woolmer]

Luke
   There was a new housing design for the Aceca in November 1959, which probably went with an aluminium cast differential housing of the same period, I assume prior to this the Aceca used a modified Ace fabricated housing, the difference being the Aceca had isolating bushes!
   I presume the Cast aluminium design reduced cabin noise!
   
   Robin

[bex1151]

Robin
   
   Thanks for the lead to Gerry. My differential is not welded to the chassis.  The entire unit, including the case, is bolted into the chassis as a complete unit.  Is this an unusual assembly? I emailed Gerry and included photos.  He wrote back that the bearing blocks need to be custom made for my unit. I assume Luke's comments are also for the welded housing but I'll see what INRacing's units are like.  Otherwise, I'll just have to find a qualified machinist.  Again, thanks for leading me to Gerry.
   
   Aloha   Terry

[Robin A Woolmer]

Assuming you have an Aceca then the diff assembly is mounted on Metalastic bushes ( which by now are a bit deteriorated & might benefit from replacement) this was done I believe to reduce cabin noise which the Ace being open does not suffer! AS it is the fabricated design & not the later aluminium casting the bearing housings should be the same as the Ace, the cast housing had the bearings captured half in a counter bored housing in the casting & half in the bearing housing, so did not need to be doweled as the bearing O/D registered it! So I would expect the In Racing parts for the Ace should be fine!
   For your information Jim Stokes Workshops did a major overhaul on an Aceca last year which had the fabricated diff housing so you might get some useful information on this issue from them, I believe they removed the housing from the chassis so may also have replaced the Metalastic bushings!
   Hope this assists
   
   Robin

[BEX298]

So this reply is an experiment on trying to post a picture following instructions from the picture thread, as well as a comment on these housings. I have also purchased new bearing housings from IN Racing, and used them without modification. I have rebuilt several Ace/Aceca rears. I have plotted the hole centers of the bearing housings for the diff stub axles for original ("left/right" in picture) and INR bearing housings ("new" in picture). The originals from both my BEX298 and an early Aceca diff/axle seem to be based on a 2-3/8 bolt centers. The original left side/right side pin locations from the same and from different cars have quite a bit of variation. The new ones from INR seem to be something else entirely. As for the dowel pin locations, I am guessing the original is a polar dimensioning scheme rather than an ordinate, but INR might have been thinking ordinate in the translation when copying for CNC machining. Though neither way works out to be a homerun for those of us that like precision. The originals and the INR new ones both work, however, because there seems to be quite a bit of play from loose tolerances. INR supplies them from the shelf with dowel pin holes already drilled, while Gerry might have realized the variance problem so recommends custom from the beginning. If the INR off the shelf won't work, then I would simply ask whoever you decide on to make them (either INR or Gerry) without drilling the dowel pin holes and then have them drilled to match your diff case. If the photo sharing doesn't work, I can just email it to you off line.. Ian
   
   

[BEX298]

Hmm, not encouraging picture-wise but at least you can click on the link and it will send you to it..

[Robin A Woolmer]

The dowels should be 1.5" centres plus or minus 0.003" equidistant about the centreline horizontally
   By 2.8" plus or minus 0.003" vertically equidistant about the centreline.
   The CNC machine should be able to hold tighter limits than this!
   I anticipate the housing fabrication may have some variability, that is probably why Gerry suggests you make the dowel locations to suit! Which is a pity!!
   Robin

[BEX298]

Unfortunately, no matter how accurate a CNC machine can be, it is only as accurate as the guy programming it....

[Robin A Woolmer]

In 1953 when these parts were made they did not have CNC machines & no calculators! If the machinists could make within tolerance then why not now?
   
   Robin

[BEX298]

My theory is - calculators. when we did things by slide rule, in our heads or by hand calculation we had better sense of the "correctness" of the results. So many little things have been forgotten that we learned from day to day work. For example, in these bearing housings we're talking about, there is a nut that holds the bearing, and this nut has a set screw. The originals have a bit of lead in the hole that prevents the set screw from buggering up the threads, and not one of the "rebuilds" I've taken apart seems to have this little piece of lead..