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Gearbox Swapping

Changing the gearbox (or the engine) for better performance is easily done if you've got the right kit.

By Julian Edgar and Michael Knowling, Photos by Julian Edgar

Click on pics to view larger images


This article was first published in August 1999.

Changing the gearbox can be a good option if you want more or different ratios, or increased gearbox strength. And while it's possible to make your own adaptors - after all, pretty well anything's possible! - it's a helluva lot easier to use an off-the-shelf gearbox swap kit. Depending on the swap involved, these can comprise a new bellhousing, clutch and clutch actuating system, or a simpler adaptor plate.

We've included at the end of this story a table with some of the different gearbox adaptors that are available, drawn from information supplied by the Castlemaine Rod Shop and Dellow Automotive. While the listing is just a small sample of the variety of kits that are available, it gives a good idea of what can be done. All the listed swaps are for RWD or longitudinally-engined four wheel drive cars - we've never seen a kit for a FWD.

So what sort of swaps are possible? Fancy a tough GM Turbo 700 4-speed auto behind your Nissan RB six? That could be an excellent swap in a scorchingly-hot Commodore VL Turbo, where the standard Nissan auto is known to get tired pretty quickly. Or, how about putting the ubiquitous Toyota Supra 5-speed behind your 2.6 litre Mitsubishi four? A strong V8 with a slick 5-speed 'box behind it is sure to give better economy - and probably better acceleration response as well. And so if you have a Holden V8, you can have any gearbox from the 4-speed auto normally found behind the Holden V6 to a Muncie, Saginaw, T10, T50, Toyota 4 & 5-speeds - or even an Alfa 5-speed!

And while these adaptors let you change the gearbox, you can also work the other way around by changing the engine while leaving the rest of the car intact. Now we don't reckon that means that a Holden V8 in an Alfa Bertone GTV will be a good swap, but - when you've butchered the car enough to fit the V8 in - it can be bolted up to the gearbox! Changing engines could be a viable option when putting a Holden 253-308 or Chev into a Jaguar XJ6, or dropping a Subaru engine into a VW, though.

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Gearbox adaptor kits come in two types - those that use a new bellhousing and those that don't. The kits that don't require a bellhousing use a thin, machine-cut steel adaptor plate like the Castlemaine Rod Shop one pictured. The plate bolts to the engine, and the gearbox then bolts to the plate. Also included can be the clutch throw-out fork and clip, thrust bearing and carrier, pivot ball and mount, spigot bush, and nuts, bolts and washers. Most gearbox swap kits also include a new speedo cable. In other words, you should be able to grab the kit, the new gearbox (or new engine!) and then be able to bolt them all together without modification. However, some conversions require alterations to the gearbox input shaft - a process normally carried out on a changeover basis. Bellhousing kits are much the same, but the bellhousing of the new gearbox needs to be replaced with the unique cast alloy item provided in the kit.

Click for larger image

The Supra 5-speed is one tough, common and cheap gearbox - it's probably the most popular one around for swaps. Just check the pic for a comparison of the bearings and synchro rings of the Supra and Holden V8 boxes! The "oval case, Supra-type alloy box 5 speed" to give it it's most widely-used name, comes in four versions, as shown below.

Ratios W55 W57 W58 W59
1st 3.57 3.28 3.28 3.95
2nd 2.06 1.89 1.89 2.14
3rd 1.38 1.27 1.27 1.27
4th 1.00 1.00 1.00 1.00
5th 0.85 0.86 0.78 0.85

The gearboxes weigh 35kg, use a front shaft 21 spines x 29mm, are 56cm long, have a tailshaft spline number of 21, and take 2.5 litres of oil. Of the different types, Dellow Automotive list the W55 and the W59 as being the most commonly available.

Some of the factors that need to be considered when undertaking a gearbox swap are:

  • The gear stick position with new 'box - will it come out through the floor or the firewall?
  • The size and shape of the trans tunnel in relation to the new gearbox. Dellow Automotive recommend approximately 25mm clearance between the box and car body. (The trans tunnel can of course be modified, but it is better to avoid this if possible.)
  • How robust the new gearbox is, and how much power will be lost through it.
  • Whether the flywheel needs to be changed to suit the new gearbox.
  • The cost of the conversion. Dellow conversions range from about A$550 to A$3500.
  • Does the tailshaft length need to be altered? For example, fitting most Japanese 5-speeds behind a Holden 5 litre V8 won't require any tailshaft length mods, but fitting the same 'box to a six cylinder will probably need a shortened shaft.
  • Whether the speedo output needs to be modified using a "reduction box", or the speedo unit itself recalibrated.
  • Whether a new clutch cable or booster system is needed to operate the new clutch.

Incidentally, while we were talking to Dellow, we discovered that they are close to releasing a kit to put a Supra manual (we're not sure if it's the six-speed!) behind the Lexus/Soarer 4 litre 1UZ-FE V8. The housing will cost around A$400-450. This should make wrecker imported Lexus V8s even more appealing!

Step by Step

So how does a gearbox conversion come together? We watched DAT Racing's John Keen fit a Supra 5-speed to the Holden V8 in a HZ ute using a Dellow Automotive kit.

Click for larger image

The original gearbox was the "Aussie" 4-speed, a gearbox known for its poor strength. In fact, this gearbox is happier behind the Holden six which develops far less torque. Incidentally, it is the peak torque of the engine - not its power - that dictates gearbox durability.

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The first step in the swapping of the gearboxes is the removal of the original box. The boot and selector mechanism were removed, and then the gearbox bolts were undone, the box slid backwards and then dropped off.

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So what do you do with a grotty, unloved and worn-out gearbox? One-way trip to the scrap metal merchant.... Note that this gearbox uses a cable-operated clutch. The Toyota box uses hydraulic actuation, and so the gearbox conversion in this case also involved changing the clutch operation from cable to hydraulic.

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This is what the alloy Supra 5-speed looks like. It's available from importers in either used as-is form, or having been disassembled and checked.

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The Dellow kit contains the bellhousing, pilot bush, pivot ball, clutch fork, thrust race and carrier, clutch and pressure plate, speedo cable, tailshaft yoke, dust inspection cover, and rear crossmember bracket. A Dellow kit to perform the hydraulic clutch conversion was also bought. In plain language - everything's here that you need!

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The newly machined flywheel was next into place, complete with its new spigot bush to match the Toyota gearbox input shaft.

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A heavy duty Holden 1-toner pressure plate was installed, and then it was time to....

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.....bolt the new adaptor bellhousing to the Supra gearbox.

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The Toyota thrust bearing and release fork were then fitted within the new bellhousing.

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The hydraulic slave cylinder provided in the kit is made by PBR - so it's neither Toyota or Holden!

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Next, the brake booster assembly was removed and the firewall marked out to take the bracket for the new master cylinder.

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When installed, the master cylinder and its hydraulic reservoir were a tight fit.

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The Holden gearbox mount was re-used, but the oil gunk from the old gearbox needed to be removed first!

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The Toyota gearbox then went into place, later to be supported by the gearbox crossmember.

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The standard Holden crossmember and mount were retained, keeping everything under the car neat and tidy. Normally the exhaust would need no modification, but the car was treated to a new set of extractors at the same time as the gearbox swap was being made, so explaining the open pipes.

Some Swaps!

Engine Gearbox
Chrysler Hemi six or V8 (up to 360cid) Toyota 4 & 5-speed
Chrysler Hemi six or V8 (up to 360cid) Muncie, Saginaw, T10 or T50
Chrysler Hemi six or V8 (up to 360cid) Ford linkage Toploader and Borg Warner single rail
Chrysler Hemi six or V8 (up to 360cid) Holden 3 & 4-speed
Holden V8 GM T5
Holden 253/308 V8 Powerglide turbo hydro 350 & 400
Holden 308 V8 (turbo bolt pattern), small or big block Chev GM Trimatic
Chev V8

(and Holden 308, Buick, Pontiac and Oldsmobile available)
Mazda T & E 4100, Ford Trader 0811
Holden or Chev V8 Borg Warner T5
Toyota "Hemi" V8 auto bellhousing Toyota 4 and 5-speed
Ford 289-351 V8 Powerglide, Turbo 350, 400 & 700
Small and big block Chev Nissan C80
Holden 253-308 and Chevy Holden V6 4-speed auto
Leyland P76 V8 Powerglide, Turbo 350, 400 & 700
Chrysler 392 Hemi Chrysler 727 Torqueflite
Ford with Toploader pattern Tremec 5-speed
Ford 419 - 460 V8 Ford ZF 5-speed
Chrysler narrow block V8 Powerglide, Turbo 350, 400 & 700
Holden 253 and early 308 V8 Muncie, Saginaw, T10 or T50
Holden 253 and early 308 V8 Toyota steel case 4 & 5-speed
Chev or Holden 308 (turbo) V8 Ford linkage Toploader and Borg Warner single rail
Holden 253 and early 308 V8 Ford linkage Toploader and Borg Warner single rail
Chev V8 Muncie, Saginaw, T10 or T50
Holden 253 and early 308 V8 Leyland P76 or Chrysler single rail
Chev V8 Alfa 5-speed
Holden 253 and early 308 V8 Alfa 5-speed
Chev or Holden 308 (turbo) V8 Toyota steel cased 4 & 5-speed
Ford V8 late Windsor and Cleveland (not 400cid) Toploader or Borg Warner 4-speed
Ford V8 late Windsor and Cleveland (not 400cid) Toyota steel cased 4 & 5-speed
Holden 253-308 or Chev Jaguar 12 FMX
Jaguar V12 Toyota Supra 5-speed
Jaguar six Toyota Supra 5-speed
Mitsubishi 2.6 four Toyota Supra 5-speed
Datsun L-series fours and sixes VW transaxle
Ford 2 litre Pinto Toyota 4 and 5-speed
Ford 1600 four Toyota steel cased 4 and 5-speed
Mazda 12A and 13B rotary VW transaxle
Ford 1600, 2 litre & V6 Toyota Supra alloy case 4 & 5-speed
Subaru E71 1400 and 1600 VW transaxle
Datsun A series Toyota 5-speed
Mazda 12A and 13B Toyota Supra 5-speed
Volvo B21 Toyota Supra 5-speed
Falcon/Cortina six (early, narrow bolted) Toyota RT81-RT104 & Mark II Corona 4-speed and Toyota steel-cased 5-speed
Falcon six (wide block) G60 Nissan
Chrysler Hemi six G60 Nissan
Ford V6 Toyota steel cased 4 & 5-speed
Chrysler Hemi 245-265 six Powerglide, Turbo 350, 400 & 700
Hemi narrow block 245-265 six Chrysler 727 & 904
Nissan RB sixes Holden V6 4-speed auto
Nissan RB sixes Powerglide, Turbo 350, 400 and 700
Nissan RB sixes Toyota steel case 4 & 5-speed
Nissan RB sixes GM Muncie, Saginaw, T10, T5G
Nissan RB sixes Toyota Supra 5-speed
Nissan RB sixes Ford Toploader and Borg Warner single rail
Nissan RB sixes Toyota Supra 5-speed
Falcon six (pre EA) Powerglide, Turbo 350, 400 and 700
Holden 3.8 V6 Toyota Supra 5-speed
Holden six/Starfire four 1600/180B/200B Datsun 4-speed
Holden six/Starfire four 240K/240C/240Z/260Z/280Z Datsun 4 and 5-speed
Holden six/Starfire four 1600 Toyota Celica alloy
Holden six/Starfire four RT104 & 2000 Celica 5-speed
Holden six/Starfire four Sigma 5-speed
Holden six/Starfire four Gemini 4 and 5-speed
Holden six/Starfire four Turbo 350 & 400, Powerglide, Turbo 700
Holden six/Starfire four Toyota Crown 4-speed auto
Holden six/Starfire four GM T5
Holden six/Starfire four Holden V6 4-speed auto
Holden six/Starfire four All Toyota with detachable bellhousings
Holden six/Starfire four Mazda 4 & 5-speed
Holden six/Starfire four Alfa 5-speed
Holden six/Starfire four Muncie, Saginaw, T10 or T50
Holden six/Starfire four VW transaxle
Holden six/Starfire four Ford linkage Toyota or Borg Warner single rail

Contacts:

DAT Racing
+618 8277 4222

Castlemaine Rod Shop
+618 35472 2853

Dellow Automotive
+618 29774 4419

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