Revision as of 01:05, 11 January 2013

With A-series gearboxes getting less common, you might consider a transmission swap. With the Nissan 71-Series Transmission, we have lots of choices include 6-speed gearboxes and stumpy gearboxes that use stock tailshafts. Or non-Nissan brand transmissions can be swapped in behind the A12.

1 Overview
2 Common Swaps
3 Tunnel Consideration
4 Adapter Plate
5 Expoxy Method
6 Cut & Shut
- 6.1 Milling Method
- 6.2 Shaft Alignment Method

Overview

When comptemplating a swap to another type of transmission, the following parts are needed:

Transmission of choice
Clutch disc, pressure plate, release bearing, and pilot bushing for the end of the crankshaft. It is recommended that you buy all new. They can be reused, but only recommended if they are in known good condition.
Driveshaft (tailshaft/propeller shaft) to fit both your Differential and the transmission
Rear mount (gearbox mount)
Slave cylinder and slave push rod to match the new transmission
Release arm and release bearing sleeve to match the new transmission
Speedometer cable to match the new transmission and your speedometer

If converting an automatic-equipped car to manual transmission you need:

The brake/clutch pedal assembly, complete with all hardware and springs, from the same model car you have now
Flywheel & clutch pilot bushing

See main article: Manual transmission conversion

If you have cable clutch and the new transmission requires a hydraulic clutch linkage:

Clutch Master cylinder and Slave cylinder. The cylinders may be bought new, as they are inexpensive and you know they will not be worn out.
Hydraulic hard line. A pre-made section of brake hard line may be bought and bent to fit.
Hydraulic flexible hose

Considerations:

Length of transmission
Shifter location
Speedometer cable. Is it on the same side? If on the passenger side, you might need a longer cable.

Common Swaps

Common swaps include:

Datsun B210 5-speed for A14 (63-series)
Datsun B310 5-speeds for A14/A15 (60-series)
Toyota 5-speed using Dellow bellhousing for A-series
Automatic Transmission
Manual transmission conversion for automatic-equipped 1200s

For information on common swaps see: 5-Speeds

This article will focus on swaps adapting non-A-series transmissions to fit.

Tunnel Consideration

A standard Datsun 1200 has a small central tunnel, limiting the gearboxes that will fit. However, automatic-equipped Datsun 1200s have a very large tunnel that will accomodate most gearboxes and still allow the factory heater to work.

See main article: Tunnel

Adapter Plate

How about a good-old fashioned adapter plate? This is how it was done when I was younger. They swapped any kind of gearbox to any kind of engine.

An adapter plate bolts to the engine, then using a 2nd set of bolt holes the transmission is bolted to it.

here is a Hewland adapter plate:

Expoxy Method

To make an A-series bellhousing, cut off an A-series front case, fill it with epoxy, and machine it flat. Then bolt it to the transmission, still using the A-series throwout arm.

Cut & Shut

Cut-and-shut is where the front part of the new transmission is cut off, and a cut-off part of an A-series transmission is welded to it.

Just cut the bellhousing and weld on a fragment of A-series bell housing, then machine the input shaft smaller.

Silva S15 6-Speed gearbox modified for use with A12 engine

As with any adaption, aligning the adapter is critical. It must be:

parallel to the transmission and rear engine faces
Centered exactly on the crank/input centerlines

The tolerance is very low, so this must be a precision fitting to avoid clutch vibration and early gearbox wear.

Milling Method

Cut the front case of transmission approximately
Remove front case
Mill the cut parallel to the face of the case
Repeat for A-series bell-fragment
Weld a circular plate to the case
Center the bell fragment on the plate and weld it

Centering can be done with careful use of dividers and precision measuring.

Shaft Alignment Method

Make a shaft to go in an old A-series engine block where the crankshaft would go. Weld a perpendicular flange on the end. It must be very accurately at right angle to the shaft.

NOTE: photos of L-series engine. But A-series will be similar

Remove the front case from the transmission.

Insert into the engine block and bolt the transmission front case to it. This needs to be very secure so that no play is magnified down along the shaft. Precision is very important in gearbox alignment.