Why the Doug Nash 4+1, and why in a G-body?

The 4+1 is not an overdrive transmission. The benefits of the 4+1 (now Richmond 5 speed) are price ($500-$800 used) and closely spaced gear ratios: 3.27, 2.13, 1.57, 1.24, 1 to 1 in 5th. This trans was developed to replace Muncies in 1960s muscle cars. Muncies have very low first gear ratios (low 2.xx) so the rearend gears were very high (4.10, 4.56, etc). To swap in the 4+1 they changed the high rearend gears for a ~2.73 gear and ended up with the same acceleration in 1st through 4th and had 5th as a cruising gear (hence the name 4+1). The beauty for G-body owners is we have low rearend gears already (or junkyards full of them). It's similar to overdrive but instead of overdriving the rearend you're raising the ratios of the transmission gears - different method, same result. Some luxury German cars are geared this way.

This is a record of the parts, trials and tribulations from my swap from a TH250C to a Doug Nash 4+1 in my '80 El Camino:

Overall it was not a hard swap - swappers before me posted online the parts they used: I want to return the favor.

• DNE (now Richmond) 4+1 (research shows it was purchased from Jegs in '86) 3.27/2.13/1.57/1.24/1 ratios
• Richmond Manual Transmission Fluid (2 quarts)
• Long shifter (the best shifter - has spherical rod ends) HN1000
• Lakewood Bellhousing 15020 (3rd Generation F-body SFI Approved)
• Summit G1341 Pilot Bearing (also Summit alignment tool)
• Hays 10-130 Flywheel 168 tooth
• Hays 11" 40-221 Clutch Disc
• Hays 11" 34-618 Pressure Plate (eBay score!)
• Hays 70-201 Self Aligning Throwout Bearing
• GM 3790556 Ball Stud (1.78" long)
• GM 14075725 Clutch Fork (3rd Generation F-body)
• Brakeware 10380 Aluminum Slave Cylinder (3rd Generation F-body)
• GM 12559912 Clutch Master Cylinder & Braided Line (4th Generation F-body; Stock slave not used due to header interference) Braided line drilled out to remove restriction
• Bzdel Clutch Pedal (trimmed brake pedal)
• Motormite 20734 pedal pads (Stock Manual G-body)
• Iceman TH700-R4 crossmember notched to clear the back of the transmission
• Standard TH350 rubber transmission mount
• 32 Spline Transmission Yoke (driveshaft length is OK)
• Hooker 2451 headers
• Mr. Gasket small shifter boot

Notes: I did not check bellhousing runout, but I don't have vibration in the high gears so I got lucky. I did use a "self-aligning" throwout bearing. So far so good. Hydraulic clutch linkage is possible due to John Bzdel's fabricated pedal. The longer ball stud was necessary to get enough travel. I did have to grind on the slave cylinder to clear the headers (notched the end). Unplug grinder after use: cutoff wheels cut skin even faster than metal (3 stitches).

After a few months here are some notes: be sure the shifter is secure to the transmission - the bolts tend to back out due to shifting and vibration. The clutch pedal actuation is somewhat stiff and the shifting is "notchy" but I was expecting both. A Centerforce clutch may have helped the stiff pedal but I didn't want to risk a parts mismatch - I already had the Hays flywheel. My wife says the pedal doesn't seem too stiff but I wonder what she'd say after a bit of stop and go traffic. I'm fine with the pedal and I actually like the Muncie-like shifting quality.

Helpful links:
Jay Orbison's ROD swap
Marc Hichens' Garage Scene Home Page
Marc Hichens' Manual Transmission Monte Showcase
Chevy High Performance article on a TKO into a 5th generation El Camino
J. Matthew Daugherty's Monte List T5 Tech Article
J. Matthew Daugherty's Bellhousing Photos
Iceman Crossmembers
Malibu North's G-body Bellhousings & Clutch Linkage Parts (dead link?)
Steve Ragusa's World Class T5 Conversion
Speed Direct's Clutch Linkage with Spherical Rod Ends
Novak Hydraulic Slave Cylinder Conversion
T56 into a Monte (This site is down, check Google's cache for the data.)
Google's cache of Jeff's 833 4 speed Overdrive into a '78 Cutlass.

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