5 speed conversion

Discussion in 'Modified Shizzle' started by redoxide, Feb 21, 2015.

  1. redoxide

    redoxide Guest

    Im collecting stuff for a subaru conversion on my modified camper ( which is a van conversion )

    I was thinking about the Full bell housing conversion but having thought about it, is there any reason not to use the subaru 5 speed and tgake advantage of the range of gears matched to the engine ...

    I appreciate you need to swap the ring and pinion but looking into this it appears the ring and pinion are around $1500 with the current exchange rate that works out a couple of hundred more than the bell housing..

    I can fabricate a cradle mount and exhaust headers and shorten and maintain the sump capacity saving a few quid on conversion cost which would easy offset the cost of the gears..

    But are there any other pitfalls ?

    Is there a suitable VW 5 speed transaxle

    would it be better to change the VW transaxle ratio to drop the revs ? It appears the only disadvantage to the subaru onversion is the higher revs at cruising speed.. any thoughts....
  2. redoxide

    redoxide Guest

    Pony and skirk like this.
  3. The subarugears conversion is widely used on T25s now. Loads of happy customers on the US forums from the sound of it.

    The 1-5 ratios are nearly the same as a 5 speed t25 box. You'll be running much less revs at a given speed with the subaru box than with a bay 4 speed. Approx 1000rpm less at 70.
    The final drive ratio is either 1:3.9, 1:4.111 or 1:4.444 so about the same as those in a stock beetle box.:thumbsup:
    Not sure how those ratios would cope with pushing a van shaped lump through the air though compared to a car sized vehicle. I suppse the extra power and torque of a subaru engine will help.

    Theres someone on a US site with a twin turbo'd 3.3 flat 6 subaru going in a bay pickup. He reckons on 4-500bhp.:eek:

    Theres also the UN1 gearbox as fitted to Renault 25, and loads of sports and supercars but if you're going subaru engine anyway then you might aswell stick with a matching gearbox.
    Poptop2 likes this.
  4. redoxide

    redoxide Guest

    I saw the UN1 box swap too. but it was pretty muh a swap for swap sake if you already had the subby box.

    I did think about the car gears trying to shove along the brick like aerodynamics and weight of a van, and thought that the extra revs with the stock T2 box might be good enough, after all any mod or swap is a bit of a compromise ... Also I underestimated the cost of the crown wheel and pinion swap ... It would be getting on for almost £900 more than a bellhousing swap... and with car gearing and all the selector issues to overcome , it may not be the best option... alos looked at the VW Passat gearbox .. Im a long way off from commencing any swap so plenty time to research and work out the best "compromise " for my needs... lets face it, lowered shiny 40 plus year old bus isnt going to be doing regular road duties... T2 box would be the path of least resistance... Any benefits of fitting a 6 rib box ? do they have better ratios? can the revs be smoothed out with a different tyre size ?

    Loads of research and questions to be answered

    Looking at the subaru gears subby box conversion I didnt like the long selector shaft support and couldnt work out why they didnt shorten the housing and shaft to suit?
  5. Baysearcher

    Baysearcher [secret moderator]

    @Moons will know what difference the 6 rib box makes as he swapped one for his original 3 rib on his EJ20 bus.
  6. redoxide

    redoxide Guest

    How would keeping a 4 speed but trading up to a freeway flyer, what difference would that make....
  7. Baysearcher

    Baysearcher [secret moderator]

    A few on here have had longer 3rds and 4ths fitted I think.
    No idea about the freeway flyer.
  8. I swapped a 3 rib box for a 6 rib and though I can't quote the revs it's much more pleasant at cruising speed and better suited through all the gears. Not Subaru though.
  9. Moons

    Moons Moderator

    The issue with the Subarygears conversion in a bay is you need to modify the chassis rails and the firewall/bulkhead area, it needs custom driveshafts and cable linkages for gears and clutch.

    The benefits are that the Scooby boxes are numerous and cheap.

    Regarding the 3 rib and ratios - mine was plenty strong enough, the gear ratios were the issue.

    Before (3 rib boggo box)

    After - 6 rib box longer 3rd and 4th


    Most significant when it comes to engine being on cam:

    art b, Pony, paradox and 1 other person like this.
  10. How does a "freeway flyer " differ from a regular 6 rib? Longer ratios on 4th?
  11. Moons

    Moons Moderator

    I thought a freeway flyer was a 3 rib - in any event, it's a longer 4th that makes them desirable.

    One issue with them is they tend to be on exchange only - so you need a 6 rib box to swap or you can't get one if they are 3 and 6 rib.

    I forgot to mention - mine whines a bit of overrun in 3rd and less so in 4th - but certainly not silent, @rickyrooo1 finely attuned hearing immediately picked up on it, though it was more challenging form me as I had to try and hear it over his whining abut work, life, house , Eastenders plots etc etc.

    I had it checked by Bears, they built it originally - they reckon that 3rd especially is louder because they are made for sandrail races and are a little thicker or straighter cut (can't recall exact terminology, it should get quieter as things bed in) *

    * please note this is an explanation given to be by the builders - not my version of reality - please feel free to question it, but try not imagine I care.
    art b and Poptop2 like this.
  12. rickyrooo1

    rickyrooo1 Hanging round like a bad smell

    what did you think of the murder being done by bobby?
    Moons likes this.
  13. redoxide

    redoxide Guest

    I keep going aaway and looking for more info on the gear ratio stuff but its hard to find any definitve answers , there is a lot of conflicting evidence or ideas .

    Im a VW novice so definately not up to speed on gearbox types, ratios or final drives, but from what I read so far Im kinda thinking a 5 speed wont be required for the use to which the bus will be put ... Its not going to be a daily driver .

    The second thing that seems to be pointed out regularly if im reading it right and not getting confused between the spec of 3/5/6 rib boxes is that 4th gear is already an overdrive , which would negate the need to go any taller as I dint think I would be looking to cruise any faster than 70 ish ;).

    Third, again if im reading the masses of info correctly, the final drive ratios in a lot of the boxes are numerically high... which would be the main reason for high revs . High revs being good for the small air cooled motors to maintain cooling efficiency, and the pulling power of a relatively low powered engine...

    Reading more about the freeway flyer boxes it looks as if 4th is taller with the increased gap between 3rd and 4th compensated by fitting a taller 3rd spreading the err gear spread wider over the 4 speed box , which works as shown by the figures on the pictures above, but dang, those boxes aint cheep .. and would I be right in thinking there for squeezing more speed and less revs from a stock air cooled motor ?

    If the engine torque and power are increased and there is no requirement for air cooling it appears the answer to dropping the revs is to fit a numerically lower final drive, going from the likes of 4:8:1 ( pulled out of mid air) to 3:8:1 ( again pulled from the ether) fitting a slightly taller tyre also helps... if I interpret what ive read so far correctly..

    So would it be fair to say that given 120 bhp water cooled subaru engine running a standard T2 gearbox with 3:8:1 final drive on 195 65 15 rubber would pretty much be as close as one could get to a straightforward swap with the best that can be expected for pulling, cruising, acceleration and fuel economy from this particular conversion ?

    I wouldnt want to be draging, or doing burn outs or racing down the fast lane chasing porkies or seeking fast 1/4 mile times... simply looking for reliable fuel efficient modern improvement over the air cooled engine and something a wee bit different from the normal, for no good reason other than the hell of it and the challenge, how else would I fill my time :thinking:

    crikey its confusing, but probably really important to get it sorted now for getting the best from any conversion.. :)
    Last edited by a moderator: Feb 22, 2015
  14. Baysearcher

    Baysearcher [secret moderator]

    I've got a document showing all the internal specs of all the available VW boxes if you want it.
  15. redoxide

    redoxide Guest

    That would be ace. I found the following via a google search which has been usefull for Identifying various boxes ... Have to say a 5 speed doesnt look as if its required .


    a 3:8:1 diff would be one answer ... err I think... looks like the T2 is 5:38:1, that would make it rev....the 6 rib is 4:56:1... that would drop the revs a bit too... but where do you look for the right box? plenty 6 rib side shift T25 boxes about but not many tailshift T2 6 rib up for grabs.. Still a high ration though for a bigger motor .... ????
    Last edited by a moderator: Feb 22, 2015
  16. Baysearcher

    Baysearcher [secret moderator]

    Send me an email address and I'll send it all tomorrow mate.
  17. Porsche 915... They have a 3.88:1 R&P :cool:
  18. redoxide

    redoxide Guest

    Ive got a couple of Type 3 boxes here... wonder what ratios they are ?
  19. Poptop2

    Poptop2 Moderator

    How did a fairey overdrive work?
  20. Poptop2

    Poptop2 Moderator

    Sorry. Never meant to quote you there. Just wondered if the fairey o/d system was something that could be adapted to a bay, I seem to remember people fitting them to Stags and similar.

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