T3 Gearbox Help required

[madeinbrechin]

Hello,

I live and work in Baku, Azerbaijan and stumbled across an advert for a 1988 T3 selling for £1500. The van was in good condition cosmetically, as they don't use salt on the roads here there is little to no rust... unfortunately that's about as far as my mechanical knowledge goes.
I took the van to a garage, with a local friend and they suggest I replace the 1.6L Diesel VW Golf engine for a refurbished 1.9L Diesel 2002 VW Golf engine they could purchase from Dubai for me. This unfortunately would mean changing the gearbox as well, so I'm told as the existing gearbox is a 4-shift and they'd be looking to install a 5-shift instead. Can anyone give me any advice on which gearbox I'd be looking to purchase which would be suitable for the 2002 1.9L Golf engine and how much that should cost approximately? Can any one forsee any other parts requiring replacement so I'm not caught off guard.

Thank you.

[Oldiebut goodie]

I wouldn't change to a 5 speed for no reason. Doubtless Aidan, or someone else in the know, will be along with the facts and figures. I would use it with the 4 speed and change it later if you find the gearing is unsuitable. One more gear doesn't neccessarily mean that you have a higher top speed if that is the reason that they are saying change it. You would have to change all the gear shift system also if you were to fit a 5 speed.
It would help if you could get the gearbox code that is on there presently and someone would be able to say what is better/more suitable than that.Was the Golf engine just a 1.6 or a 1,6TD? Or more to the point if the gearbox is original, what was the original engine in the van?
( Mine is running on a 5 speed as that was what was originally fitted to the 1.6TD engine that mine started with.)

[Mr Bean]

Yes I agree with all of that additionally on the basis that in the eqrly days the the five speed on my WBX failed on me and then again subsequent to a rebuild (not one of Aidan's I hasten to add) and the chap who repaired it under warranty couldn't get hold of a replacement casting which resulting in me getting the damaged casting off him and boring and bushing it in the area of the selector linear bearing gismo's plus a bit of detective work sourcing some springy ball cage thingy stuff.
I mention this as the experience has left me with a feint whiff of rocking horse poo in terms of parts and rebuilds on the five speed. Could be wrong of course. but if it ain't busted maybe one job at a time would be the way to go.

[ajsimmo]

To me the theory of switching to a 5 speed when increasing the engine output is counter-intuitive. The 5sp has closer ratios which are better suited to the lower output engines (a lot of CS and KY vans had 5sp box for this reason). If you have more grunt, you'll pull through a larger gap between gears much more easily. What really matters is the gearing in top gear, which can be greatly improved where needed by fitting larger (or smaller!) wheel/tyre combos.
As an additional downside, more power and torque combined with a low geared 5 speed often tempts the well-meaning driver to pull away in 2nd gear, causing accelerated wear whilst effectively rendering it an inappropriately geared 4 speed.
But that's just my tuppence worth. I may not find much support for the theory.

Sent from my ONEPLUS A3003 using Tapatalk

[Aidan]

if it's a turbo diesel engine then a 5 speed makes sense as closer gears means less loss of revs between gears so keeping the turbo spooled up and making for a smoother drive hence most TDs had a 5 speed box and TD Syncros and 2wds with a 4 speed box had a higher ratio final drive and a taller 4th gear (compared to petrol and n/a diesels) so they accelerate quicker and then jump a bit to top gear by which time the momentum/inertia of the vehicle helps it to pull the 4th gear from a lower point in the rev range than top gear would be in a 5 speed and with the taller 4th gear they rev at very similar revs at 60mph to the petrol Syncro and 2wd 4 speeds and TD five speeds. However it is a compromise (no choice in the Syncro) and what I have seen is trashed 4th gears due to them being lugged using the torque of the TD to accelerate from low revs instead of driver changing down and revving like you have to do with a 4 speed petrol box. Hence I have no good used 0.78 fourth gears on the shelf and haven't had for several years and that ratio gearset is now pretty much no longer available.

If the OPs potential new engine is to be a TDi then the turbo spool argument applies but the engine is effectively rev limited compared to a petrol or n/a diesel or TD diesel so as well as the five speed being preferred you need a shorter final drive ratio to be able to achieve a good Vmax. That's why the aftermarket 4.14 final drive crown and pinion sets were developed to allow TDi to make 70mph whilst utilising the torque appropriately, all 5 gears and keeping revs in the low 3000s at high speeds

In answer to the OPs question there is no ideal 5 speed box if the engine is a TDi, the tallest geared 5 speed the AAP from a 2.1 petrol van isn't really geared tall enough to get the most from the engine, certainly not in UK driving; they are pretty rare, sought after so tend to be pricy, and many of them have been destroyed by cheapskate TDi conversions and people pulling away in 2nd using the torque and a cloud of unburnt fuel out the back, so if that is what is proposed then any good core 5 speed box will do and then it wants rebuilding with a 4.14 final drive and maybe depending on weight/style of van and tyre size and engine installation quality a taller 5th gear, plus the SA oiling plates to help protect the new crown and pinion set and 4th and 5th gears at speed, and a proper mainshaft bearing retention solution if it to be long-lived and nice to drive

This experience may not apply in other countries where motorway work is not done and the landscape is much more challenging

A proper TDi spec built box would cost way more than the OP paid for the van

just mho and yemv of course

[jebiga41]

As Aidan has stated the ideal would be a 5 speed with a 4,14 Crown and pinion SA oiling plates to protect it and 4th and 5th gears, a HD 4/5th slider and mainshaft bearing retainer for increased longevity I would also a Dual MAss Flywheel to further protect the gearbox from those nasty TDI torque waves a TDI input shaft and a TDI starter and adapter plate. All of which is not cheap (will definitely cost more than what you paid for the van) but will future proof your box. Just as it happens I have come across a few 5 speed boxes recently so I am in a position to do one or two outright sale or exchange boxes, of course, these can be tailored to your needs either PM me or drop me an email at vwvantopia@gmail.com Paul

[madeinbrechin]

Guys,

Thank you all for the in depth replies. They are very helpful. The engine is not a turbo diesel, but the mechanics working on the van are looking to source a turbo for me... though this may now be redundant if I intend to keep the van as a 4-speed for now. I have no way of knowing which engine was originally in the van, though the mechanic suspects it may have even been a petrol engine and not even a diesel one. The engine we took out wasn't original and was also a VW Golf, but a 1.6L and not a TD. I'm guessing the VIN wouldn't give me any indication of original engine type/size?

We believe the gearbox to be original, but not too sure. My Azeri is very limited as is their English. Explaining anything technical, when all of this is new to me, will be a major challenge, probably impossible.

This maybe wasn't be best idea in the world but it's a learning experience and we'll come through the other end in some shape or form!