Hi everyone,

I have a Polo 86C Coupé with an MH engine, and it currently has an 8P (085) 5-speed gearbox installed.

I would like to replace it with a QR 4-speed gearbox, because it has shorter gearing and I’m hoping for better acceleration.

My question is:

Do I need to modify anything for this swap, or is it plug & play?
For example:

• Do I need a different clutch or pressure plate?

• Do the driveshafts / flanges from the 8P fit the QR gearbox as well?

• Does the shifter linkage / gear selector system need to be changed?

• Are there any other important differences between these gearboxes?

If anyone has experience swapping a 5-speed to a 4-speed (or the other way around) in an 86C, I’d really appreciate your advice.

Thanks in advance!

Good question, I think the QR is a Mk1 box, so I think you'll need to change at least the gearbox mount, the nearside driveshaft, and your speedo will probably end up a mile out.

The be fair, 8P's are geared pretty well in 1st-3rd, it's just after that they get a bit tall (5th was designed to be like an overdrive - do your acceleration in 4th, then drop it in 5th for economy). If you want closer, I'd look for a gearbox off a 2f GT which would drop straight in apart from maybe putting the speedo out, and it's a different plug for the reverse light switch.

The MH's are a pretty lazy engine, if you want to actually go faster, look at the cam and the fuelling.

Edited 14 February Feb 14 by Yeti

It’s for racing, so I need the closest-ratio gearbox — a 5-speed is out of the question for me. I already have the top mount, and I don’t care that the speedo won’t match after the swap.

My main concern is the driveshaft:
Can a Polo 1 driveshaft fit in a Polo 2 chassis with the QR/Mk1 gearbox, or is there something different about the lenght that stops a direct fit?

Also, how certain are you that the original 8P driveshafts do not fit the QR? I’ve seen conflicting info on that.

I’ve also heard that the release bearing or even the whole clutch setup needs to be changed when swapping between 5- and 4-speed. Is that true? Does the QR require a different bearing or pressure plate compared to what the 8P uses?

Thanks!

If it is rod change, will fit fine. You could even screw a metal plate at gear lever to keep to H pattern and stop you trying to select 5th.

Same splines for the driveshafts but Mk1 shafts are shorter because Mk1 track (Spurweite) is 1.296m but Mk2 track is 1.320m.

Worthwhile changing the release bearing when refit a gearbox.

Inspect the guide tube it moves along too and change that if worn. Then you know you won't have to take the gearbox off just for a noisy release bearing.

New starter motor bush in the gearbox housing.

I suggest to change that off the car. I use a big bolt and a cable tie folded into the hole. Keep turning the bolt clockwise. The bolt cuts a thread in the nylon and brass then winds out the bush when it bottoms.

If in the car you have to lean over for access and it can take ages to remove such a tiny piece of metal.

Linked advert suggest release bearing only changed after May 1986 and used for MH engine.

eBay UK

Audi 50, VW Polo Mk1, Derby, Golf Mk1 1.3 NOS Borg & Beck...

(Polo Mk1, Derby 1.05 (GL engine) chassis no. G-050 001 on, up to 5/1986. Polo Mk1, Derby 1.3 (MH engine) engine no's 001 001-008 561 / 051 001-052 706, UP TO 7/1985 models. Golf Mk1 1.3 (MH engine) e

Pressure plate will depend on pins and holes in the flywheel, not the gearbox.

I assume 190mm mk2 clutch will fit a QR bellhousing no problem.

If you change to a new lightened flywheel you will likely need a different starter motor so the bendix can engage with the pinion ring gear teeth.

The anti roll bar will have enough clearance. Not the case going from 084 to 085.

Edited 15 February Feb 15 by dvderlm

52 minutes ago, dvderlm said:

assume 190mm mk2 clutch will fit a QR bellhousing no problem.

Larkspeed only sells 180mm 24 spline performance clutches ( diameter of friction disc)for the Audi 50... so you will have to measure how much bigger the existing pressure plate is.