Transmission Swaps

(Difference between revisions)

Revision as of 08:03, 2 January 2012

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.

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 tranmissions 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 tranmission is bolted to it.

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

1. Cut the front case of transmission approximately
2. Remove front case
3. Mill the cut parallel to the face of the case
4. Repeat for A-series bell-fragment
5. Weld a circular plate to the case
6. 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.

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.

Cut the transmission case aproximately as much off as needed. You could do it with stationary grinding wheel while rotating the case on the shaft.

Bolt the A-series fragment to the block too

Rotate the case appropriately and weld together.