Do a search on my name and Gear Vendors and you should find decent info.
The overdrive is .78 (22%) and is the equivalent of making a 4.10 gear like a 3.20.
There is a delay .8-1.0 seconds for the unit to engage, so for racing use a computer with an air shifter would be a necessity.
One last thing, in my Chevelle I did need to cut the floorpan and rather than use the standard "tube-type" crossmember I used one from a 68-72 GTO ("stamped type"), so I did not have to make any crossmember modifications. The stamped type crossmembers were in most 68-72 skylarks, GTOs, Cutlass.
I installed 1 of these on the back of the T-400 in my 72. It works awesome but I did have to rework the floor a little bit and also modify my tubular crossmember. I made my crossmember similar to the one shown in the Jan. 2001 issue of Car Craft. I mounted a round rocker switch to an aluminum housing I machined to fit the factory floor shifter and even tho it's only been in about a month it seems as tho I don't even think about it when I use it. They are a little pricey however, luckily I found a used one! Defineitely a nice piece.
I am not sure what a tubular cross member is. My car came originaly with a powerglide so I am not sure what type of cross member this is.
Is the cross member modification something that you can do at home, or do you have to take it somewhere to be modified? Also, would my powerglide cross member work, or would I have to go with a TH-400 one if I went with the 400 tranny.
Any Chevelle I've ever seen (only familiar w/68-72 - many) had a crossmember made out of bent to shape oval tubing. Apparently other GM A bodies used crossmembers stamped out of sheetmetal. The modification involves cutting a notch in the tubing by the trans mount bracket and then boxing this notch with angle iron to reinforce the crossmember. It's not hard to do if you or a friend has welding and cutting equiptment and skills. If not, probably easier to locate one of the flatter stamped crossmembers. I didn't bother looking for one as conv. crossmembers are different and harder to come by. I'm pretty sure the powerglide crossmember will work, just slide it back to a different set of holes in the frame. Hope this helps, Jim.
I'm using my original crossmember and did not have to "massage" the floor pan either. I fabbed up a new trans to crossmember mount that lowers the rear of the OD unit about an inch or so. No problems so far. It has been on the car for a year now.
68 Malibu B&M blown 350, TH350 with 10" converter and Gear Vendors overdrive, 12 bolt-3.90 gears
69 CST Pickup original 396, TH400 factory AC/PS/PB
99 Harley Dyna Wide Glide
91 Sportster 883- now a 1200!
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