Manual transmission conversion -- 4 to 5 speed, etc.


New member
I have a 86 Westy with a 4 speed transmission. Is there a way to upgrade the trans to a 5 speed? I normally cruise the freeway at 75 mph and the engine is running at a high rpm.
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Capt. Mike

VW's 5 speed Type 094 transmission does NOT give you any significant differences in 5th gear over your current 4th. The difference was in gear spacing, primarily for the lower power of the diesel. The gap between 2nd & 3rd on a VW is already too high.

The VW Type 094-4WD transmission is commonly referred to as a 5-speed but it does not change ratios except to provide a granny gear extra low and reverse.

Short of a custom transmission modification or adapting to another manufacture, there is little you can do "backyard". Costs of a custom are probably astromical -- you'll have to hit the Hot VW crowd. That's outide the scope of this site.

Also, bear in mind that the power of the VW doesn't allow much of a ratio reduction. Current is about .85:1. Even the high performance trannies like a Porsche are only in the .8:1 range -- they usually combine the higher power with a different rear end ratio. And then you won't have the power to get going because the reduction will be across all the gears.

Any changes would require significant linkage differences, even the VW 5-speed.

[Suggest you read the thread under ENGINES about breaking in a new or reman. It has some valuable discussion of VW driving speeds and techniques. If you're running at 75 mph true -- about 4200-4300 RPM -- you'll be spending a lot of time in the shop -- "green" arc on the tach not withstanding.]


New member
I searched the archives, but this is the only thread I've seen about switching transmissions. I realize it may take a little work, but how hard would it be to fit a Porsche 912 5spd into a '77 Westy? Would it provide any benefits? None of the Porsches I've seen had a granny gear, but were fairly quick off the line and still had a decent top end so I'm thinking the ratios must be slightly tighter. Any comments?

Capt. Mike

Porsche transmissions, even if the bell-housing to engine matched -- I don't have ready resources to say -- and the clutch size, clearance and activation are compatible, use a different size drive axle. The CV joints won't match up. Porsche uses a 4x10mm bolt gasketed flange compared to VW's 6x8mm bolt unsealed flange. Porsche's are a larger diameter and probably thicker. This means you would require custom transmission output shafts and stub axle shafts as well as new (and surely custom) half-shafts. The new stub axles must also match VW's rear bearings and spline arrangements. (The 912 has rear disk brakes vs. VW's drums.)

Since both use a transaxle, you cannot divorce the final drive ratio from the gear ratios. The 5-sp 912 ratios are 3.09, 1.89, 1.32, 1.04 & 0.86 1st through 5th respectively, driving a 4.43 rear axle ratio. The VW is 3.80, 2.06, 1.26 & .89 1st through 4th gears driving a 4.86 rear axle ratio.

Thus start off -- not a VW strong point -- would drop from 18.47:1 to 13.69:1. That's a health loss of low end power. 5th would give you 3.81:1 vs. VW's 4.32:1 top gear, a 12% decrease in engine speed, but would the VW have enough power to pull it? You have over a 30% lower power difference.

The idea of a 5 speed to close up the wide gaps in gears is admirable but final results in starting up will have to be close or you'll never get off the line without frying the clutch. Top end is going to be limited by the power available to overcome the box-through-molasses aerodynamics of a VW bus. Even when VW offered the 5-speed, it only closed the gear ratio spacing; it did not change lower & upper gears signifigantly.

And finally you have to balance cost. A 912 tranny and the conversion costs are more than the typical Type II is worth. Yes (when new), you could get custom ratios for the Porsche tranny. But again at what monsterous costs. You'd probably be better off checking out the race VW shops for custom or converted VW transmissions.
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New member
That's pretty much what I figured.

I did find a site on where someone had put an entire Porsche engine and 5spd tranny into an earlier bus. He had to use some spacers (the hub to hub distance is less) and do some modifying of the linkage to get it to work but stated it really wasn't worth the effort. I think I'll just rebuild my current transmission and live with it. Sometimes modifications are great, sometimes not.


New member
Does any one know if it is possible to install a 5 speed from a diesel in a 2.0 aircooled? i do a lot of mountain traveling in a heavy camper and would like gears to have less space between them. i figure that if i could find one in a junkyard i'd just take the whole shifting assembly too. just a thought. thank you.


New member
Change Axle Ratio

Does anybody know anything more about transmissions?
Is it possible to change the axle ratio of a vw transmission by installing a custom made gear.
I'd liek to put a TDi engien into my bus, but these engines top out at 4000 rpm ut have loads of torque. If The axle ratio could be changed from 4.86 to 3.61 it seems like it would be possible to change the entire gearing.The question is if that is possilbe at at all.


New member
091/1? to 091 (yea, right...right?)

Hi, new to the board, did a search and didn’t find any idiocy related to my dilemma…..

Can someone please confirm that a 091 trany from an ‘81 will not (“easily”) swap with a 091/1 on my ‘84.

I feel so stupid right now after looking at a Bentley book that (after spending $300 to get the 091 thinking that that a 6 rib is a 6 rib is a 6 rib and an ‘81 would replace my busted ‘84) I’m not embarrassed to ask anything and hope for a miracle.


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Dharma Too

New member
I too have an 86 Westy with a manual 4 speed and wanted to find out that since mine appears to need rebuilding anyway I wanted to find out if there was a way to upgrade to a 5 speed and would it benefit my Westy? Did you ever find any good answers to your post?