All - searched but could not find....talking about this in Tranny forum too, but knew there'd be expertise here too.....going to install Gear Vendor Overdrive on the back of TH400 in 71 Chevelle. Have to increase the tunnel clearance by about 1/4 in in two 4" areas. Looking for suggestions on the easiest and cleanest method/tool. Thinking about trying portapower unit. Thanks for your help.

Assume you are talking about the rear of the tunnel where it tapers down to meet up with the floor boards. If correct, you can cut out a piece wide enough to give yourself the clearance you need. Cut along both edges about 1" above the flat floor and across the top of the rear tunnel, then cut back to where the rear of the tunnel meets the rear floorboard and across so the piece can be removed like a cap.

Then shape a piece of sheet metal that is taller than the piece you cut out and reduce/extend the taper towards the rear to give you the clearance you need. Then taper it or drop it down to meet the floorboard somewhere beyond the original cut. Weld it all back up and then weld the underside too, seal and enjoy.

You are going to sacrifice some legroom in the back seat area and may have to have the rear carpet modified or made to fit the new rear center tunnel. Do you have a console also? Shouldn't be a problem although the console may sit a little higher in the rear.

You could forget all about the gear vendor and just get a 200/700R4. Maybe not the easiest way.

Bitchin sheet metal products has removeable tunnel covers that bolt on or can be welded on if permanent. You might want to look at one of those and cut out the preformed piece you need and then weld it into your old tunnel rather than forming a new piece by hand. I think the tunnel covers sold for about $60 bucks once upon a time.

Otherwise I would think you could adjust the pinion angle 1/4" and leave it all alone with out causing too many problems. You can sit the engine lower in the car by getting rid of the rubber engine mounts and bolt it up solid. Should drop the engine down 1"-2", but makes for a "shaker".

OK I am all out of ideas someone elses turn. I suppose you could "stretch the metal" where the G/V hits and see if you can gain more room as well, if you don't mind seeing the dents from under the car. OK now I really am out of ideas. LOL

Good Luck,

A 5lb hammer and a block of wood

Thanks!

OH I get it you meant really, really easy. LOL