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Meithered to death
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Discussion Starter #1 (Edited by Moderator)
Recently installed a 1.9TDI motor from a golf into my T4 and also changed the 5th gear from the golf into my T4 gearbox to give a higher top speed and lower RPM at cruising speed. Original ratio was .78:1 and the golf TDI was .71:1
You need to identify the gearbox by reading the code ontop of the box beneath the gear selector rod then you can find out on the net or from VW what ratio your 5th gear is as T4 came with varying ratio's depending on engine size and style of van(800 1000 1200 caravelle etc). Golf TDI's came with a higher ratio's throughout all the gears but you can only swap 5th without a complete box strip down and rebuild.
You will need a 3 leg puller and similar 2 leg puller to remove the syncrohub from the mainshaft and to remove the cog from the layshaft.Also recommend an airgun to undo the retaining bolts at the end of each shaft.
Firstly jackup your van on the passenger side and remove the front wheel to get easier access to the end of the gearbox,some T4's have an undertray which is quite difficult to remove unless the van is on a lift/ramp.
Here's how to swap the 5th gear cogs!
Clean the gearbox end cover so you can get onto all five securing bolts easier and to ensure no dirt gets into the box.Then undo the five bolts and remove the cover,be ready with a catch container as some oil is sure to spill out.
I changed mine whilst the engine and box were out so the pics are a little different.
The gearbox end cover and five securing bolts easily visible


Once the cover is of you can clearly see the 5th gears and syncro hub and selector mechanism,mainshaft is much bigger and carries the syncro,layshaft is much more basic.


Next undo the two small torks bolts above and below the syncro hub to free the selector from its pivots then wiggle the selector arm free from its position and place it in the previously removed end cover for safe and clean keeping.
It will then look like this


Now if you havnt already done so then its a good time to take some pics of the syncrohub and the selector slider that slips over it,there are two spring rings(one inside and one out) and three locators (the little rectanglular things)Once youve taken the pics for reference in the reassembly then grab the slider by hand and pull it of the syncro hub and put the bits in a safe clean place again like before.

slider and three locators removed(but only two visible in this poor photo and maybe not so clean and safe)


Now i mentioned airgun earlier here's when you need it,undo the big 6sided torks bolt in the middle of the mainshaft and the one in the middle of the layshaft while your at it.Then use the 3leg puller to remove the syncrohub and 5th gear cog together from the mainshaft.Inside the cog or on the shaft you will find the needle roller bearing as this cog is not fixed on the mainshaft and its the splined syncro that holds it there along with the torks bolt already removed.

The bolt in the layshaft in this pic is just for the 2leg puller to push against

Next use the 2leg puller to remove the smaller gear on the layshaft


Then you have both the 5th gear cogs removed completely.
Clean everything you have removed (except for the two cogs you are changing) ready to go back in,you need to re-use the syncrohub,slider and locators again.

TO BE CONTINUED................
 

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Re: How to-5th gear upgrade!

once again, top workA:A: what gear box did you get the higher ratio from tho? is it the one from your tdi donor?
 

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Re: How to-5th gear upgrade!

Sounds like a great idea for Motorway Mileage !

Just out of interest, what sort of difference would you expect in MPG on a motorway run if you were doing the same speeds (70-80 ish?)
 

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Discussion Starter #4
Re: How to-5th gear upgrade!

once again, top workA:A: what gear box did you get the higher ratio from tho? is it the one from your tdi donor?
yea pulled 5th from it before i scrapped the rest as the diff pin had dropped and ruined the other gears but 5th is well out of the way from the debris so i could salvage it.
 

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Discussion Starter #5
Re: How to-5th gear upgrade!

Sounds like a great idea for Motorway Mileage !

Just out of interest, what sort of difference would you expect in MPG on a motorway run if you were doing the same speeds (70-80 ish?)
Not sure on any solid figures but the theory works - less RPM-same speed= better MPG and less stress on the motor as it isnt reving as high.
 

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Re: How to-5th gear upgrade!

sounds good, wonder how much it would cost (labour hours) to get it done at a garage ?
My spanners only do pipes and fittings, they don't do engines :D
 

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Re: How to-5th gear upgrade!

sounds good, wonder how much it would cost (labour hours) to get it done at a garage ?
My spanners only do pipes and fittings, they don't do engines :D
Dont imagine you would need alot of tools, its only basic hand tools and the pullers you can hire anywhere T: great to be able to cruise at motorway speeds without haemorraging money......A:
 

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Re: How to-5th gear upgrade!

fantastic that Aggie .. just so happens i have a mk3 tdi gearbox sitting in my garage .. was going to ebay the bugger but i think ive just found another use for it .. T:
 

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Re: How to-5th gear upgrade!

Hi, can this be done to the 2.5 box????
On my 2.5tdi syncro the gearbox code is DRH. The 5th ratio is 0.63 to 1, but the syncro has a lower final drive so you end up with a slightly lower final drive ratio (3.095 to 1) than a 2.5tdi 2WD in 5th (2.95 to 1)

However if you used the 5th out the DRH box in a 2WD (If it fits!!!) you would end up with a final drive ratio of 2.65 to 1. This would give you nearly 29MPH per 1000RPM in 5th, normally you get just under 26MPH per 1000RPM.

So 100 MPH would be at just under 3.5k revs and a potential max of 127 MPH at 4400RPM if you could get there? Its normally 114 MPH at 4400RPM.
 

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Discussion Starter #12 (Edited)
Re: How to-5th gear upgrade!

Hi, can this be done to the 2.5 box????
Depends on which gearbox yours has,some 2.5TDi's have a non vw box fitted(same as boxer/relay/ducato) the easiest way to tell is if reverse gear is right and back on the stick rather than left and forward then you have this non vw box and the operation is completely different and not one i am familiar with.However if its the vw box then operation is the same although 2.5's are geared different to the 1.9's you would have to research your gearing and find a suitable 5th gear ratio to install.

My original 5th gear ratio was .78:1 and i changed to .71:1 from the golf TDI gearbox.
 

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Re: How to-5th gear upgrade!

Dont imagine you would need alot of tools, its only basic hand tools and the pullers you can hire anywhere T: great to be able to cruise at motorway speeds without haemorraging money......A:

It's not really the tools that are the problem, it's the operator !
 

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Discussion Starter #18
Re: How to-5th gear upgrade!

aggie, can this 5th gear up grade be done on an early 2.4 caravelle ?
Yes i think so if it has the VW gearbox,check the end of the gearbox to see if it has the black bolt off removeable cover with the VW emblem stamped in it.
 

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Re: How to-5th gear upgrade!

hi, thanks for your responce, it is s vw box & the code is , as far as i can make out, C H S which seems to have ratio of 756-1. as this up grade seems possable, from which outher vws could the 5th gear train be sorced do you know ?
 

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Re: How to-5th gear upgrade!

what an exelent mod,
well thought out ,and very well detailed ill look into this my self.
my hats off to you.
cheers dave
 
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