I've seen that most T-34 have the cast differential gear covers (rounded edges), but I've seen welded differential covers ("hard" edges) in some tanks as well. I want to know a little more about the latter, were these covers used by any factory? or maybe they were used only by one of them. I have the Tamiya T-34/76 ChTZ (I think UTZ is the correct designation), 1943 production, and I know that the hull depicted in the kit is a Nº 183 Factory hull, but It comes with welded differential gears covers, If they're not situable for that hull, It will be easy to make the modifications. Thanks a lot in advance. Best regards.

José.

Well, Factory 183 did use a cast part that had more of an angled cross section and this is one of the types provided in the Tamiya kit.
I believe 183 was the only producer of the T-34 to use this type. (I could be wrong here but I’m “fairly” sure it was only they.)
The kit part can be improved by making the angled face rougher (it looks to have been torch cut from its casting gate) with a Dremel and ball headed bit and maybe a little putty. See some of hte photos Dmitry provided in his section on rear hinges to get an idea of what I mean.
BTW, the diameter of the housing should be a little larger than the kit has it. This can easily be built up with some plastic strip to build the outside face.
As far as welded housings go, yes, there were some but if I recall correctly they mostly show up on early-ish Model '41 hulls also from Factory 183 (correct me if I'm wrong here). These were built up from rolled strip and flat plate.

Mark