Hello All. Hoping that a gearbox expert might be able to shed some light on this topic and conundrum for me. In short I'm puttting a 20v turbo into my T4. The existing gearbox ratios are poo and while they'll work okish an upgrade will seriously help with drivability. I know of one person who has successfully transplanted a G60 final drive into a T4 gearbox (02B) but unfortrunately it was done by a gearbox specialist and they don't know the detail. I've checked the ratios against my T4 box and I think it would work quite well with the overall ratios and speed ending up very similar to a G60. Far more drivable. BUT, I'd be really grateful of some assistance on the detail, potential problems, etc. on this. Way out of my comfort zone here. Thanks
The main gearbox area casings are very similar, however the differential area of the 02A and 02B is very different. The diff casing is much larger on the 02B, and the fact the 02B uses a shaft extension so the drivers side driveshaft is the same length as the nearside means the output flanges will vary on that side. The diff casing is much larger to house the lower ratio final drive used in the van, IE larger ring gear with more teeth. I would imaging the planet and sun gears might be bigger to cope with the load carrying capacity of the van compared to the car. Some one with EKTA may be able to cross reference these parts. It could be that the installation of an 02A differential is possible in the casing, with it utilising the 02B output shafts and flange components. This would mean changing the gearbox output shaft to fit the corresponding one to match the final drive being installed, this is because the ring gear and pinion are a set and match together. These are pics of the T4 box I have here that I looked at last year or so.
Thanks danster. Good to see that there's the benefit of having someone who's familiar with both boxes. Space obviously isn't an issue as the van housing is much larger. That's a start and the fact that it's already been done is also good news. Just need the detail. Hoping this might help. Here's some pictures of the diffs and gearboxes of both. T4 Gearbox Corrado Box T4 Diff Corrado Diff
Done some digging. Not that it helps much! However, interestingly it seems the early T4 boxes (pre 1993 or so) shared the main gearbox propshaft with the Golf / Corrado etc. So that's a start. Final drive is obviously different. However I'm wondering if the centres for the output shaft and pinion gear are the same across the 02A and 02B? If so that means that it was all down to gear sizes and the swap looks easier. Any thoughts Danster? I'll look to see what's common elsewhere next.
I would imagine fitting the gearbox output shaft and corresponding ring gear from the 02A to the 02B box is possible as the gearset area of the two gearboxes looks the same. It just depends whether the ring gear from the 02A fits the 02B differential, or possibly that the 02A differential fits the 02B casing and accepts the output / drive flange components from the 02B as well.
Yup that's pretty much where I am at the moment. Internals are the same between the 02A and 02B boxes. Up to 1993 anyway and possibly 1996. After that the 02G box was introduced on the T4's. So it looks like I can combine the "front end" (for want of a better word) but it's the diff where the problems lie. it's definitely not obvious that's for sure. Diff housing and pinion are bigger on the T4 as Danster has explained above. For reference I found a sweet cutaway picture of an 02A gearbox. Makes understanding teh layout a little easier, for me at least!
What's the length of that 02B shaft extension? Could it be fitted to an 02A in a golf to allow the use of equal length drive shafts?
The extension looks like it is bolted to a belhousing gearbox half, reminiscent of an 02C, ie the 4WD syncro box. So a bellhousing swap would necessitate. Also the extension would need anchoring to the engine block. Brackets would be bespoke.
Not quite. I don't know the length but the but it does equalise the lengths of the drive shafts. You'd need to check the connectiosn to the CV joints. There's chance they may be different although the boot kits are common between the Golf and T4. With regard to the bracket. Get one off a 1.9 diesel, 1.8 petrol or even a 2.0L petrol T4 (pre 1996) and it will fit the Golf block (Mk 3 and back). They are the same and my T4 is essentially a fat Golf. As Chris says how you marry the extension shaft to the rear of the diff is a completely different matter though. No idea there.
^I think you'll find thats an 02J (or at least the shifter tower and gearbox casing is... not that there's much difference) Goes back to stroking white Persian cat...
Have you actually checked to see what alternative ratios the 02B gearbox came with? There are possibly taller gear ratios available that could raise the gearing. Best find out what gearbox code you have and what gear and final drive ratios you have to start with, then a decision could be made on the best way forward.
yeah I initially started down that route. Quite a few to choose from. Unfortunately having found the right gearbox and looked at getting it refurbed it would have better use in the scrap bin. Slight problem is taller ratio 02B boxes are hard to find but it's still an option. The other complication is the mounts. They changed. Not the end of the world but something else to think about. The 02G gearboxes off the later T4's (post 2000 I think) would be a further option. Stronger and good ratios but again the mounts are an issue and I'd have to change the drive shafts and whatever else that brings with it. My interest in changing the final drive stems from another 20v turbo conversion and they have managed to swap the final drives using one from a G60. Unfortunately they don't know the detail. The benefit of this route is I can use my existing gearbox casing and gears. I can also use any input end items from the 02A and the gears match closely to the car when done. That should make it a comfortable drive (hoping). I'm still looking but I may just opt for a higher final drive from the scrap 02B box I have if it's salvagable. It's an interesting topic though.
Now Im stalking you in two different forums. You wouldnt have a part number for that bracket would you as I can't figure it out in Etka.
Careful I'll have to report you to the forum police. Part I think is 02B 409 905K off the 02B gearboxes.
I remembered a lad had a 4wd transfer box for sale a while back. Comparing pics looks close to being a fit. Question is, was there ever 4wd T4 vans?
Yes there was from 1993 to 2004. The T4 Syncro. Here's the gearbox etc. on one. Transfer hub replaces the extension arm.
