broke 8.75

[rat roaster]

I took out my 8.75 today after it blew up on sunday at the track.Both bearing caps were broken. It looks like a cap broke and then it took out the gear set. Has anyone else had this happen and why did it happen?
No tranny brake. Its a 4.89 case.I foot brake 1.62 / 60ft. The pinion bearings seem to be ok ,it seems like the left cap broke inbetween the bolts , then the right cap broke on one side only.The gears I feel by looking at them were ok till the cap let go.It tried to come out the back of the houseing.

[PRO]

Is the gear missing any teeth?any rollers missing from the bearings? if so what usually happens is the broken teeth or rollers get between the pinion and ring gear and force the carrier to twist which results in broken caps,look at the ring gear wear pattern,is it centered in the teeth? if not it wasnt setup right.Were they original gears,you know 30 yr old steel gets brittle,I had this happen on an original 3.91 set dated 1967 and just cruising around it snapped a tooth,hope this helps......PRO....

[T748]

I had a bearing cap bust in my truck awile back. Here is the thread from it.
http://www.moparchat.com/forums/show...threadid=31387

[duster360]

how fast does the car go? how much does it weigh? unfortunantly the 8 3/4 can only handle so much horse power. i have seen several 9.00 cars that weigh over 3000# bust the caps. you got to remember these units are over 20 years old.

[JANDJ]

Did it look like this?

I changed to this and have had good luck so far
But I think anytime you are using an 8.75 in a heavy car that puts out some power you are at risk of that problem. The caps are from Mark Williams.

[T748]

Those aftermarket caps look good! Do they and the housing need a trip to the machine shop before use or can you just bolt them right up? -Tom.

[JANDJ]

They are sent a little big you just bolt them into the housing and take a measurement side to side and up and down then remove what is needed to make the bearing surface round. Very easy if I can tell my drunkin machinest neighbor how much to mill of the mating surface and he has if for me the next day it cant be to hard by the way that was about 100 passes ago, I hate to even jinx it by saying that.

[rat roaster]

The car weighs 3572 with me in it. It runs 11.60s at around 115.86 mph and 60fts in 1.62. Was going to try and get low 11s next year. Its a street car (no nitrous). I have been looking at the MW caps I may try them. I would love a Dana 60 . Will see what the budget allows, I have priced out some new Danas (through Magazine Advertisers) and I am looking at $2200.00 us dollars thats $3000.00 Canadian Ouch. But a couple of blown up 8.75 s and Ill be part way there. What to do?

[Hammer 74]

I saw JandJ's before and after in person and the Mark Williams caps look much beefier than the stock ones. For the money they are the way to go.

[rat roaster]

By the way Jandj my 8.75 did look like that. My crown gear wasnt as bad as yours but both my caps were broken. Left cap (drivers side) was completely broke and the right one (passenger side) was only broke on one side.What a waste of a good gear set.

[rat roaster]

Phoned Mark Williams and they said. Bolt the 8.75 together properly and use our caps and adjusters and 600 hp should be no problem. I think they probably wanted a spool in it. I have the clutch type posi,Anyone broke one of those with too much hp input? How much hp will the clutch posi handle?