Transmission Swap Details

Years ago I swapped out my 700R4 for a Doug Nash 5 speed manual (that was the design predecessor to the current Richmond transmissions; Richmond Gear bought Doug Nash out).

More recently, I upgraded to a Richmond Gear 6 speed to add overdrive. The Centerforce clutch parts and 5 speed you see above were removed from service at that time. The new 6 speed (below) looks very similar to the old 5 speed, save for the updated tail housing sporting an extra shift arm. With the 5 speed the frontmost arm controlled 5th gear and Reverse. Now all the gears in the main case are forward speeds, and the reverse gear is in the tailhousing.

Lots of big and little things had to be dealt with. Mostly, I was able to use 1980-1981 GM manual transmission application parts (e.g., clutch linkage, pedals, etc.), though I went with Centerforce for the clutch. Cutting the hole in the transmission tunnel was a little challenging, and if I had to do it again I'd lay more towels and stuff in the car to keep the sparks and filings under better control. Probably the most surprising aspect was that my 1982 crossmember didn't fit up with the new transmission, so we swapped in a mid-70s crossmember with two exhaust holes and custom fabricated the rear mount using some hardware from another car. This, of course, mandated the exhaust system had to be swapped out for a true dual arrangement. The down side to a custom exhaust is that the factory pipes were good (stainless) and the quality of custom work I have been able to get since has left something to be desired.

The only issues with switching the 5 speed for the 6 speed were an inch or so relocation rearward of the rear tranny mount pad, slight modification to the shifter to make the handle angle back a little bit, and rounding of the shifter ball nut for comfort.

I swapped out the factory bellhousing for a Lakewood blow-proof unit, but that wasn't really necessary. I had read something about the possibility of clutch explosions in high performance applications, and I figured what the heck...

The 6 speed works and looks like it was made in the car by the factory! Plenty of off-the-line baloney boiling, hide hazing torque, yet on the highway, I go about 70 MPH at 2000 RPM in overdrive. It's a great combo at both ends!

You can get exact specifications and measurements right from Richmond. They're on the web at: http://www.richmondgear.com

Regarding parts, here's what I have now. Where I used GM parts, they were generally items used in the factory 4 speed '80 and '81 cars.

GM clutch/brake pedals.
GM 4 speed clutch linkage (rods, Z-bar, stud, clutch fork).
Miscellaneous springs keep the linkage tight and pull the pedal up.
Centerforce throwout bearing.
Centerforce Dual Friction 11" clutch.
Ram steel flywheel.
Mr. Gasket roller pilot bearing.
Lakewood "blow proof" bellhousing.
ARP bolts/studs.
Richmond Gear 6 speed, 3.26:1 1st, 0.76:1 overdrive.
Long 6 speed shifter (supplied with tranny), modified slightly.
Rubber "accordion" shift boots for tunnel hole & fork from Discount Auto.
Spliced wiring to adapt my backup lights to the Richmond switch.
Dinosaur oil in the tranny (I heard bad things about using synthetic).
GM C4 Corvette tail yoke.
Spicer non-cross-drilled U-joints.
Coleman custom driveshaft.

I spent a lot of time making sure the flywheel was perfectly perpendicular to the driveshaft centerline (reputedly the trick for ensuring long clutch life and smooth operation). I filed on the rear of the crankshaft, and test-mounted the flywheel many, many times. Other than that, things just bolted together.

Tough to nail the total cost down, as the above was accumulated over two separate swaps. The Richmond 6 (with shifter) is $2700 , the clutch a few hundred, and maybe $1000 or so for everything else. It is a labor-intensive job, but nothing a serious enthusiast can't do in a few weekends.

Date last updated: June 10, 2003

NCarboni@ProDigitalSoftware.com