Looking for advice on these differential bearing caps

[HAWAIIZR-1]

http://i78.photobucket.com/albums/j86/hawaiizr1/DSC01735.jpg

These cracks don't look right to me. Do I need new caps?

http://i78.photobucket.com/albums/j86/hawaiizr1/DSC01738.jpg

Here is the other side. This can't be normal. Only 53K miles (as far as I know) on this differential.

Thanks for any advice or input from those that know and have experience working on differentials.:cheers:

[tccrab]

If they're just casting marks I wouldn't be too concerned.
If they're cracks I'd think seriously about replacing them.

Has this diff ever been out of the car before?

TomC
'Crabs

[carter200]

Craig,
Have the machine shop magnaflux the caps to be sure the "cracks" aren't an issue.

[HAWAIIZR-1]

If they're just casting marks I wouldn't be too concerned.
If they're cracks I'd think seriously about replacing them.

Has this diff ever been out of the car before?

TomC
'Crabs

Thanks Tom, these concern me and don't look like casting marks but hoping some of the folks that just did there might be able to chime in. As far as I could tell, it seemed like the first time out of the car based on all the bolts and condition of the other items like the half shaft ujoints, etc. They were almost one with the yokes.

[HAWAIIZR-1]

Craig,
Have the machine shop magnaflux the caps to be sure the "cracks" aren't an issue.

Carter,

Thanks, good idea and I do have to go there to take all my bottom half stuff next week when I get the shipment. They look pretty wicked and I'll look into new ones just in case.

[Jagdpanzer]

Given that the caps are obviously of none ferromagnetic material I'm afraid you will find magnafluxing ineffective. Dye penetrant inspection would be the more appropriate method. I've been through a few C4 Dana 44s and have to agree with Crabs, what you are looking at are marks left over from the casting process. A little rubbing with 400 grit should make them go away. If not then you really do have a crack.

[flyin ryan]

Given that the caps are obviously of none ferromagnetic material I'm afraid you will find magnafluxing ineffective. Dye penetrant inspection would be the more appropriate method. Exactly right...What you need to do is often refered to as 'Zyglo'.

[GOLDCYLON]

Wow those look like cracks to me. Thanks Ryan and JP I had no idea how you would inspect these beyond magna fluxing. I would ask JVD hes seen a few rear teardowns before

[HAWAIIZR-1]

Thanks for the advice and I'll try it out. How hard is it to find the dye? I'll check around. Worst case scenario I found these, but a little pricey:

http://cgi.ebay.com/ebaymotors/1985-96-Corvette-Dana-44-HD-Billet-Steel-Bearing-Caps_W0QQitemZ390112828555QQcmdZViewItemQQptZMotor s_Car_Truck_Parts_Accessories?hash=item5ad4895c8b

[HAWAIIZR-1]

Given that the caps are obviously of none ferromagnetic material I'm afraid you will find magnafluxing ineffective. Dye penetrant inspection would be the more appropriate method. I've been through a few C4 Dana 44s and have to agree with Crabs, what you are looking at are marks left over from the casting process. A little rubbing with 400 grit should make them go away. If not then you really do have a crack.

So the caps looked like this on all the ones that you worked on? These really look like cracks and I'll go in the garage now to check it and hit it with some 400 grit as suggested.

[Jagdpanzer]

Craig,
Before going to the trouble of crack testing see if the lines will clean up with a little sanding and buffiing. If they do then you are good to go.

Here is a source for a dye penetrant inspection kit.
http://www.cylinderheadsupply.com/spbyma.html

[Jagdpanzer]

So the caps looked like this on all the ones that you worked on? These really look like cracks and I'll go in the garage now to check it and hit it with some 400 grit as suggested.

Yes

[Polo-1]

look the same as the 3 I've done.

[flyin ryan]

Craig...if you do buy those billet caps, don't think they are 100% for sure just going to bolt on without at least checking to make sure the housing bore is 'Round' with the caps in place & TQ'ed up. It's like our cam cover's, don't want to mix them up. Little more leway with a rearend bearing because of it's race, but I'd still check...

All you really need is one cap anyways, if you were trying to save a buck. All the rearends I've done, 85% of the time I put a good cap on the one side that takes the major load, Billet caps on both sides is a little extreme unless you've got 16x32's out back :cool:.

[HAWAIIZR-1]

Thanks Phil, Kevin and Ryan,

I did a little sanding with 400 grit and I think these are not cracks but will check them again on another day. I sanded a few of the light ones and it appears to get smooth, but the big ones are not really going away and will try to take a better look with light and magnifying glass to see it better. I have a feeling it is as stated and if folks have see it before then probably so and I should not worry about it. I have enough problems and cost already.............

Happy New Year!!! :occasion1

[4DSZR1]

if you compare the lines we're talking about on each cap with the other cap you can see that they both have the same lines in the same relative spot, indicating casting marks.... looks like casting lines to me.

[1991ZR1]

I have similar lines on bearing caps on a spare Dana 44.

http://i59.photobucket.com/albums/g311/corvettez/Corvette/DSCF0159.jpg

When I asked about these lines, I got similar responses. Some people were concerned and others said that it was normal. I notice that the lines do not continue past the mold lines. I would guess that a crack would not stop at the mold lines.

[HAWAIIZR-1]

Thanks to all that replied, especially 1991ZR1; I am convinced they are castings as they look indentical to the photo posted and in the same exact areas. I guess it is time for some glasses so I can see better. Only the fine lines can be sanded off and I decided to stop on the larger ones as it was just removing material and I am already convinced. Thanks again!!!! :handshak: