Brain dead moment: Converting a FWD engine to RWD, gearboxes

[johnhenry]

Afternoon all,

Having a brain dead moment, please don't shoot me down...here we go

Last night, couple of friends and I were theoretically (dreaming) of how to build an old school style single seater racer.
Since 9am this morning ive been sat in the most dull series of presentations ever, and my mind has wandered back to the racer,

Simple engine - something relatively small cc (1.0-1. 6tops) from a FWD car, which is common, nice and small, give it a tune get a relatively good output form it.

My question is this, due to the FWD engines using a gearbox specifically for a FWD car (including the transaxle), if longitudinally mounting the engine on the rear,

how does one find a gearbox that is suitable to mate up to the engine to give the desires rear wheel drive from a longitudinally mounted engine

Many thanks
John

[Bill]

Why mount it longitudinally? Most FWD car engines won't be long enough to warrant turning it surely?

[MX7]

The easiest way is to start with a suitable donor, which is why there are a few MX5 kits around now.

[johnhenry]

the initial idea what for the engine to be very common, fairly straight forward (any modification aside) and relatively cheap to replace/work on. Also being compact was important - which is why a small 4 pot appealed.

the point was raised that if the gearbox needed to be a custom/fabricated job to mate correctly, probably an engine that is already RWD so the drivetrain is just a straight swap would be better value maybe?

The other option was to just mid mount the horizontal engine and use the transaxle + gearbox, but we thought that kind of copped out of the idea, wanted to see if it was possible to do what we wanted.

Cheers
John

[johnhenry]

MX7 said:

The easiest way is to start with a suitable donor, which is why there are a few MX5 kits around now.

mx5...really should have thought of that, considering it is a pistonheads bread and butter answer.

cheers man, good call!

[harryowl]

K series?

[mackie1]

You'll be needing a longitudinal transaxle gearbox too. One from an old Renault would probably be the cheapest, then maybe old Audi.

[crocodile tears]

harryowl said:

K series?

this was also my first thought.. It has to have been popular with lotus, caterham etc for a reason

[HughG]

The Ford Zetec has a Ford standard bellhousing bolt patterns, so these can be mounted to the type 9 bearbox from the Capri, Sierra etc for rear drive applications. Normally these are front mounted and connected to a sierra or freelander rear diff (for IRS applications) or escort/cortina is going live rear axle. I guess it would be possible to mount the diff to the gearbox without a propshaft. This will have the axle hanging out 750mm behind the rear of the engine though.

Things like Ultimas tend to use Porsche or Getrag transaxles, not cheap. Renault did an odd gearbox for one of the espaces called an NG3 which has the half shaft outputs a lot nearer the bellhousing, not sure what engines would mount to it though.

Renault NG3


and one of eBay

Edited by HughG on Thursday 1st March 13:08

[thinfourth2]

Engine in front of driver

Fit a gearbox from RWD car drive shaft to a diff which sends power to wheels

Engine behind driver

Find a transaxle from a car with a longitudinal FWD setup

OR

Engine in front of driver and you want to go really slowly

Weld up diff in FWD transfer box and run a driveshaft to a diff at the rear.

[crofty1984]

johnhenry said:

the initial idea what for the engine to be very common, fairly straight forward (any modification aside) and relatively cheap to replace/work on. Also being compact was important - which is why a small 4 pot appealed.

the point was raised that if the gearbox needed to be a custom/fabricated job to mate correctly, probably an engine that is already RWD so the drivetrain is just a straight swap would be better value maybe?

The other option was to just mid mount the horizontal engine and use the transaxle + gearbox, but we thought that kind of copped out of the idea, wanted to see if it was possible to do what we wanted.

Cheers
John

It's not uncommon to see a ford zetec (mondeo/focus) engine in a Mk 1/2 escort. You have to do something to the water rail and there's an adapter plate to fit it to a type 9 5 speed 'box. And engine mounts of course. I think retroford do a comprehensive kit.

[Megaflow]

Do you want to mount the engine in the front or rear?

If front mounted there is lots of options avaliable. However if you want to mount it lengthways in the rear, the thing become a lots more difficult.

If you want rear mounted, then I'd be looking at VW Passats and Audi A4's.

[rhinochopig]

Or fit a bike engine longitudinally and take the power off the front sprocket, via a two piece torque tube prop. If you want FE-RWD.

If you're only after circa 100-120bhp you can pick up an old 900cc /1000cc engine for a couple of hundred quid and yet get a free Seq box thrown in.

[Captain Muppet]

Megaflow said:

However if you want to mount it lengthways in the rear, the thing become a lots more difficult.

Lots of longitudinal mounted FWD Audis in scrap yards. It's an easy way to go if you want to go mid-longitudinal and RWD.

[johnhenry]

HughG said:

The Ford Zetec has a Ford standard bellhousing bolt patterns, so these can be mounted to the type 9 bearbox from the Capri, Sierra etc for rear drive applications. Normally these are front mounted and connected to a sierra or freelander rear diff (for IRS applications) or escort/cortina is going live rear axle. I guess it would be possible to mount the diff to the gearbox without a propshaft. This will have the axle hanging out 750mm behind the rear of the engine though.

Things like Ultimas tend to use Porsche or Getrag transaxles, not cheap. Renault did an odd gearbox for one of the espaces called an NG3 which has the half shaft outputs a lot nearer the bellhousing, not sure what engines would mount to it though.

Renault NG3


and one of eBay

Edited by HughG on Thursday 1st March 13:08

Ive been reading about fords having a 'standard' bellhousing pattern up to the duratec where it changed, would give great potential to change the engine if we wanted to go abit faster, wealth of engines and tuning available for ford engines.

NG3 looks an interesting prospect! Thanks for that! looks really cool! i see your point about having to mate it directly to the engine, no prop shaft, it can be done though, ill do some reading on the issue.


Thanks to all posting, really useful just to have different ideas and thoughts thrown out here!

[The_Burg]

VW Passat. longitudinal engine in some models i believe. 1.8 motor would be cheap option surely?
(Option of turbo too).

http://www.autotrader.co.uk/classified/advert/2012...

£500, engine and box etc and scrap / break the rest?

[Superhoop]

Why not use a 1.8 20v engine from a B5 Passat?

It's front engined, front wheel drive, but the engine is mounted longitudinally, and the drive shafts exit from the side of the gearbox, so perfect for your application

Want more power, change the 1.8 20v for 1.8 20v turbo unit