Do I need TA Performance cover for my 10-bolt?

I'm building a restomod '72 Cutlass convertible (frame-off restoration) and I'm currently working on the chassis & suspension. I plan to build a small block with 200-4r trans and 3.42 rear gears with a Detroit Truetrac posi carrier. My HP/TQ target is 350-400 HP and around 400 lb/ft of torque. It will be driven daily, mostly city driving (I live in Houston, Tx so lots of stop-n-go traffic). I'll be running 17" rims and tires with about 10" of tread width on the rears. Is there any advantage to running a TA cover for the extra bearing support or is this overkill for my HP/TQ level? The alternative is a repro W27 cover for the extra fluid capacity, lower operating temps, and of course just for looks! What do ya'll think?

 

Do you NEED it? Heck no. Do you WANT it? Obviously yes. And it does look really cool! If you already have it, go for it. What I'd suggest is you compare the volume the cover has vs. your original 8.5 cover. Fill both with water and see if the volumes are the same.

I went with the W27 cover on my car for exactly the reasons you outlined, and it also looks really cool.

re: daily driver and stop n go traffic? The diff won't get hot enough to worry about. Only thing you will notice is with 3.42's you'll burn a heck of a lot more gas. The 1,2,3 ratios on the 200 4R are really close to the 1,2,3 ratios of the TH350. Where the 200 4R shines is that .67:1 final drive at highway speeds. I like your plan in spite of what I've said ^^^. You'll probably have to change out your speedo drive gear on the trans with those 3.42 gears (or get a ratio adapter for the cable) , unless you're planning to use GPS for speed monitoring.

Here's a link to Speedometer World, it has some interesting info if you want to check it out.

 

They do make a 10 bolt w-27 cover repop. That's what I'm using. My buddy has the T/A cover on his skylark. I would run the olds cover on an olds.

 

They both look nice. But yeah, I'd go with the W27 cover too.



John

 

Allen & John:
I prefer the W27 cover (and the price is about half of the TA cover). However, the TA cover has 2 bolts that apply a pre-load to the carrier bearing caps inside the differential to strengthen them, which the W27 cover does not. Is there any benefit to this feature for my HP/TQ level and application? Heat is a real killer here in Texas. I think the W27 cover might actually lower the operating temp more than the TA cover because of all the fins on the W27 cover.

 

For the use you described I don't think you need the extra support of the TA cover. My 2 cents

 

The W27 cover is the one I'd go with also, the 2 bolts on the T/A cover are not going to benefit you.

 

You will be fine with the W27 cover. I went 10:90's @ 122 with the W27 cover on my 8.5" 10-bolt. Now someone else is pounding on it.

 

Sorry, I was under the impression you'd already bought the TA cover. I put the W27 cover on my 72 (even though it's not correct) for 2 reasons. One is for looks, the second is for the better heat dissipation you're looking for. I realize TX can get pretty hot and the W27 does hold an extra quart of gear oil. Yes the fins should help dissipate the heat quite a bit. Up here we don't really get that hot, so the practicality of a W27 cover isn't really that noticeable.

As far as I know Parts Place has the best price (89.00) on the W27 cover. The one I bought came with the gasket and bolts. The gasket was no good (way too thin - replaced with Felpro) and the bolts weren't correct. They would work, but had separate lock washers. I simply cleaned up my OEM ones, and re-used them.

Came out looking like this (bumper is just test fitted here):


I'm not sure how much the differential would be affected by ambient heat under the car. Brian can answer that one.

 

The W27 cover will allow you to run two full quarts of fluid,and the aluminum will help dissipate heat better.
Some come with a gasket and bolts,and some do not.The prices reflect that. Just like anything else,you have to piece everything together separately to make it right. Some of the 12-bolt W27 covers come with the correct OEM gasket,but I haven't seen one with the 10-bolt. I just use black rtv silicone,and when it's dry,I trim the excess off.

 

Brian, quick question.

As you commented on the 10 bolt covers not having a good gasket, I can verify that. The one that came in the 'kit' with mine leaked, so I changed it out to a felpro. To make sure it didn't leak again I used some permatex 2 on the gasket. It doesn't leak anymore. I know that was overkill. Am I thinking correctly that the only thing this did would be to make it harder to take off when/if that time comes? From what I know P2 shouldn't dry like silicone does.

The supplied gasket was about 1/32" thick. The felpro was about 1/8"?? thick.

 

Even when I use a gasket,I still smear some silicone on each side. It acts like glue and is real sticky. Yes,it might make removal a little harder,but nothing I have leaks anywhere.

 

I had a different experience when I swapped my original 2.56 rear for a Chevy 12 bolt 3.55 rear. In-town mileage stayed exactly the same, which I attributed to the lower rear gears letting the trans shift up through the gears faster (and easier) so it got into 3rd faster. Think of riding a bicycle and trying to take off in a high gear vs. a low gear: it takes a lot more effort to get moving in the higher gear than with the lower gear.

Highway mileage was a different story, but you will have an OD gear so you won't suffer like I did.

 

I'd vote for the T/A cover, I have shelled rear main caps in these 10 bolts with less power than you are talking about. I would consider it a little bit of cheap insurance. The W-27 cover is a piece of fluff that does nothing for you but look nice.