C4 Upgrades

I did not want to steal the other thread on this subject... but.

You folks know I am currently working on my C4. It is the 68 with the small input shaft, and the factory H-Code servo.

Could I go and update to the bigger input shaft and drum assembly that it goes with? If going to Rollers, do I have to roller the entire tranni, or just the input drum components? Not touching the rear drum assembly....

I was about to start work on putting some holes in my front clutch assembly. But that would be one of the components that come with the new front drum assembly...right? So would that drum assembly need to have some holes put in it too, or will it come race ready? Are those drum assemblies selectable so I can get one set up for 5 clutchs?


This Gear Reduction kit looks very interesting to me, and since I am running 3.00 gears, This would be nice, since third gear will let me keep the highway ratio for crusings in thrid gear...right?

It is very expensive though...$600.00 Maybe I need to be talked into it.

Complete wide ratio gear kit. This kit will lower your 1st and 2nd gear ratios to 2.92 1st, 1.68 2nd for increased acceleration and pulling power. Kit includes loaded high strength forward drum with bearing, forward planet gear, forward hub and bearing, and sun gear. Does not require any machining to install. Suitable for applications up to 500 horse power and 351 cubic inches. Specify 1965-1969 or 1970up transmission. Also fits C5 models 1982up

drilling holes in the reverse drum dont really do a hole lot for it, no noticeable diffrence i have done both ether way no diffrence, but on the other hand i have never done the ratio swaps let me know how that comes out!

Mike, it's hard to tell, but I think you are building this for a street car right? So, a street car at your power level doesn't really NEED anything fancy in the transmission. It just becomes a matter of how much money you want to spend. Added clutchs in the direct drum is certainly worth something in the longevity department. If you are going to do that, the added holes in the side of the drum is alway a good idea too and it doesn't cost anything to do.

Another worthwhile upgrade is a good shift kit. That will help the trans live too. The roller bearings aren't really needed at you power level and you will not likely see any measurable benifit in the MPGs. It's just another thing to spend money on that won't show in the end result.

As for the low gear set, the theory of it sounds like a good idea since you are running a 3.00:1 rear gear. The down side is that they are very expensive. Is it worth it? It's up to you and your bank account. I'm not going to talk you into it.

Thanks CS. I just keep getting trapped in the "Should have done it right the first time" so just trying to think about things.

I drilled 4 1/4 inch holes in the front drum. They line up with the oil holes in the band. I think they came out fine....I rounded the corners with a stone really smooth.

I myself have wondered about the gear kit.
You install one and let us all now how it goes.

If you are going to install the wide ratio gear kit you are going to be putting more thrust on the #9 thrust under full throttle than normal so I would take the time to rollerize the #9. It takes all the thrust of the tranny's gear train. Drilling holes in the clutch drums is always a worthwhile exercise. There are a number of ways to get 5 clutches in the direct clutch. A TransGo 40-2 kit is a good addition to a good transmission.

Or 47-2 for the early valvebody....