Can you tell by the posting time that I often have trouble sleeping?

I run an LPW cap support cover on my 12 bolt. This device was invented quite some time ago and was called a GIESE (sp?) cover.

The idea is simple. The cover is a beefy cast aluminum rear cover with set screws that snug up to the backs of the carrier caps in order to decrease or eliminate cap deflection under power.

I was reading the Camaro tech website and one fellow made the following observations....things I never considered.
He states: When the cover heats up from driving, the preload changes, and when it does, who knows if the cover either remains effective, or actually applies too much preload to the caps and can actually cause harm. Not a direct quote, but you get the idea.

I don't know about you guys, but when I street drive my car, the rear end gets damn hot. So no doubt, the preload on these bolts changes. I'm not a metalurgest, so I'm not sure if the preload increases or decreases. And it will depend on how hot the diff gets.

I have heard of steel and alum replacement caps that are better than the stock setup. Might these be a better solution?
I have even heard of increasing the cap bolt diameter to 1/2". But it seems to me that there just isn't that much meat back there to accomplish this. I use ARP studs in mine.

Just sleepless thinking and wonder what folks think!

I know a friend uses no support cover, a steel cap on the pass side, runs low 10's and has never blown his 12 bolt up. 66 Chevelle

Is special machining required to add the steel caps? Or is it just a bolt in deal.

I'll shut up now.

Ron

Ron,
I have used the Geis cover and Summers Bros caps for over twenty years on the same 12-bolt rear end. The Summers Bros caps were installed on both sides, even though it is common practice to
use them on only one side. (Kinda seemed like purchasing only one new shoe to me.) When new cap(s) are installed, the housing bore should be honed to size. Mine just needed to be barely touched to bring into exact round. As I recall, the SB caps came with premium bolts.
I don't think heat will affect the reliability of the cover support. One thing that is extremely important when using these covers, is to be sure to only tighten the cap contact bolts finger tight. Any tighter any you will have carrier bearing failure.

The instructions that came with my rear cover said to tighten the support bolts to 10 lb/ft. That's not very tight so they would appear to be there to add additional support for the cap as it tries to move rearward than to put a meaningful amount of pressure to the cap when everything is static. Makes sense to me.

I was also told the greater benefit of these covers is that they stablize the entire center housing by providing a solid and stiff structure to the gaping hole at the back of the housing. The steel plate covers do not provide much of a stiffening action across this hole.

I seem to remember that the instructions call for about 5-7 inch lbs on the support screws....which is just like finger tight.
Thanks for the input guys.
Ron

Hey Ron454,

Got a question for you and some other racers out there, why do you guys buy full on drag parts for street duty? Your just paying double if not tripple for problems that will creep up later.
A support cover on a street car, do you have a pro gearset too! Sorry guys, I just see a lot of cash you are spending going down the tubes for you. I have the dual caps, Jegs cover and yes , preload is 10 lb.ft, Think about the expansion rates of the 3 types of metal in this area, you have aluminum, cast iron and billet steel, if you have Mark Williams caps that is, alm, willexpand & contract much quicker than the cast or billet, but the cast iron and billet will not expand as much as the alum. Yes the preload will change slightly, but if you machined the caps right on, and use good hardware for the cap supplier, you shouldn't have too many problems and use the best rear axle lube you can afford, something that moves heat better. Of course, the support cap holds more oil form the get go so this is a helper too.
Just wanted to voice my trapper.
Have fun this weekend guys and graemlins/beers.gif

John G.
O/C 9900

Got a question for you and some other racers out there, why do you guys buy full on drag parts for street duty? Your just paying double if not tripple for problems that will creep up later.
A support cover on a street car, do you have a pro gearset too! The only street driving my car sees is to and from the dragstrip. Maybe an occasional cruise in.

I would have to describe my Nova as a street legal drag car. I don't have a trailer. I don't want a trailer.

Ron

Keep on keepin on Ron, like I mentioned before, I don't mean to step on toes here! Not having a trailer does save cash, and I guess I am just getting old, I have lost 2 very good friends to street racing and it still hurts. Thanks for the reply post

John

Sent you an email John. No offense taken! BTW....street racing is stupid. That's why god invented dragstrips and Chrondex timing equipment!
Ron graemlins/beers.gif

i can tell you the covers work,my friend and racing buddy used to get a set of gears once if not twice a season racing his firebird after installing the cover he hasnt tore one up since.his car runs low 6s in the 1/8th and he uses 14x32 slicks

Someone mentioned their rear end getting real hot . . . that's a problem -- your rear end should never get that hot. 140-150* F is about the max normal temp. My 10 bolt runs 110-120* after a long street drive and is even cooler between rounds at the track.

And for reference . . . at about 120*F it becomes painful to keep touching an object. That's when you start doing damage to your body --- that's also why OSHA regulates hot water temp to 120*

If the rear end runs too hot the pinion bearing preload and/or carrier bearing preload might be excessively tight.

PS. My LPW cover requires 10 lb/ft TQ.

That was me who mentioned that my rear end gets hot. But I've never measured the temp. I can lay my hand on it, but only for e few seconds, so probably I'm actually in the ballpark!
Ron