Datsun 1200 originally fitted with automatic transmission has a much larger tunnel. It makes it easier to swap in larger transmissions or larger engines.

Overview

Comparo: Manual transmission cover vs automatic transmission cover

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Manual Tunnel is very small to fit the small stock transmissions and increase space inside the passenger compartment:

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The manual body has one piece lower dash panel with no joins whatsoever - the bellhousing part of tunnel is one piece with firewall.

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By contrast the Auto body has separate dash panel and floor. The transmission cover is spot welded in. The welding seam is clearly noticeable on the firewall at the back of the engine.

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Manual tunnel has no seam

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NOTE: Unlike a B110, the B210 has the same floor auto and manual - the stick and slushbox tunnels are the same on a B210.

Swapping Tunnel panels

You can swap the larger automatic tunnel into a manual transmission car. The B210 tunnel is nearly identical to the 1200 automatic tunnel. In turn, the 610 (180B) tunnel is nearly the same as the B210 tunnel. See #Tunnel Swaps below.

Modified Tunnel

Just take a big hammer and bang the tunnel sheet metal ("massage it") to get more clearance.

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Or cut part of the tunnel and weld on a bigger section

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You can also move the gearbox mounts back to suit various transmissions

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Maddat Tunnel

Product No TT1200SR Transmission Tunnel. Suit 1200 with SR20 or CA18 Gearbox. Comes with rubber gear stick boot. These can be installed in about half a day.

Note: fitment requires removal of heater box.

For 1200 SR conversions, it will allow the gearbox to be removed while the engine is still in the car. Very simple to install, just sit over existing tunnel, trace with texta. Then cut out inside the line by 10mm, weld the tunnel from inside the cab. From underneath now tap up that 10mm lip (can be made easier if heated up with oxy), run some seam sealer around the joint to finish off.

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Custom Tunnels

Others have successfully bolted or welded in tunnels from:

B210
Stanza (1980 510)
180B (610) Album 4224
Custom fabricated tunnels Album 3039

Tunnel Swaps

The standard B110 uses one piece lower dash. The Auto dash is two pieces (lower dash + cover).

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The rear half of the tunnel is part of the floor

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In actual practice when swapping, the "tunnel" is cut out of the dash and floor.

manual transmission 67300-H1000 ASS'Y-PANEL, dash, lower [manual transmission] 74300-H1010 ASS'Y-FLOOR, front [manual transmission]

automatic transmission 74306-H1020 ASS'Y-PANEL, A/T floor cover, front [automatic transmission] 67300-H1021 ASS'Y-PANEL, dash, lower [automatic transmission] 74300-H1021 ASS'Y-FLOOR, front [automatic transmission]

Auto Tunnel Swap

Auto tunnel is very large to fit the 71-series Automatic Transmission, but still fits under the heater box.

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Auto Tunnel retrofit - tunnel can be cut out, then the new tunnel welded to the floor & firewall:

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Shoey's diagram

https://i297.photobucket.com/albums/mm219/ddgonzal/wiki/jay_t_dim_sm.jpgPost click for topic

B210/610 Tunnel

Includes 120Y & 180B.

Fits into 1200

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Fits into a 1200 and still allows for a stock heater:

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NOTE: All B210/120Y use the larger size tunnel

However the B210 floor pans differ:

from 1200 as to where the transmissions mount points are. You can move the brackets if necessary

B210 used eight different tunnels. See Tunnel Comparison.

A10 Tunnel

Several club members have fitted an A10 Stanza tunnel to the 1200.

unfamilia:

the satnza tunnel in- looks ok, but i wouldnt recomend it as an easy swap(my first one but piggys 3rd or 4th one). 120y was most stright forward he said, but heaps of room around this one

A10 tunnel in 1200

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