I once put an up-right 1600 cc into a '77 van and it was geared too high for the motor. I would like to do the same thing again with a '75. when did they put steeper ( higher ) gearboxes in these? and If I have too, how can one lower the ratios? i.e. lower profile tires? ......?
If you mean the engine was turning over too fast and you want to
*numerically* lower your final drive ratio then you need taller tires, not lower profile ones. I'm not up on VW history much at all but some of the VW vans had reduction boxes on them to make the engines turn over a little faster. The reduction boxes *numerically* brought the final drive ratio UP. The reduction boxes are not part of the gearbox. I've never seen them but I think they are at the ends of the axles. I know some people somehow use those reduction boxes in bajas to help them get closer to a "crawl" in offroading. To get their engines into the rpm range where they're putting out good power while the vehicle is moving slower than it would normally need to move to get in that range. They also compensate for the oversized tires that offroad vehicles run.
Oh... I could see them gearing the transmission a little higher (numerically) in the vans, but I didn't know there was enough of a difference that it was noticeable. Hmm... maybe the reduction boxes I've read of are actually reduction GEARboxes as in transmissions with different gearing? I could have sworn I read that the "reduction boxes" I read about were not a part of the gearbox. Maybe I skipped one paragraph too many in that section when I was reading. I thought the original question was basically how to drop the RPMs down when putting a beetle motor in a bus by changing tire profile. If it was then I still stand by what I said about needing a taller tire rather than a shorter one. If not then sorry for the misinformation/rambling.
Part of the problem is that "higher" means different things to different folks. When OP said "higher" he meant LOWER numeric gear ratio! He's still right; it's just a different useage.
Anyhoo, back to your query. Buses, up thru the '67 model, used a separate reduction gearbox, mounted outboard on the axle (one each side).
This gave additional (higher ratio) gearing but, more important, gave the Bus higher road clearance. All these Buses still had swing axle rear ends and the inner "fulcrum" is limited in how much angle it can run at.
Beginning in '68, CV joints were used (IRS) and these Bus CV's could operate at high angles to give road clearance without using a reduction box. The additional gearing was then built into the ring and pinion.
Incidentally, the original 1940 Kubelwagen (WWII) had swing axles with reduction boxes to give road clearance and the Kubels went "anywhere".
you were right on the function and location of the reduction boxes...but you are just missing some details that will bring it all together for you.......the early buses had the reduction boxes to compensate for the lower output engines used....once the type 4 engines were being used the raitos were lowered(numerically) to give better drivability on the highway(less rpm's)....the more powerful engines did not object to "higher" gearing the way the old(type 1's) ones do...
OK... That's why I kept putting "numerically" in quotes or parentheses or whatever. I've seen this issue get confused before. So if he wants a lower *numeric* gear ratio then that means he needs taller tires instead of shorter tires. I'm positive I understand the whole gear ratio thing. As soon as I read his post I figured he was complaining about the engine revving too high when he put it in a bus. I also thought right away that it might be due to the reduction axles, and was certain that taller tires would "fix" that for him and not low profile tires like he suggested.
Mostly right but my 68 has a 1600 type 1 single port engine. (as standard in the UK ) they changed the final drive in the gear box and removed the reduction boxes.
BTW did you know that reduction boxes cause your back end to RISE as you pull away ! quirky hey.
Details please? I'm only asking because I've never had the reduction boxes. I could see the rear end raising up being a GOOD thing when you start to get stuck (to keep your "lowest point" from hanging up in the mud or whatever). I don't understand how that could be a bad thing. Hmm... thinking.... Define "the rising rear." hahahah Yeah, I realize I'm stepping into this one... But seriously... "rising rear..." I've read something about this before... With a "normal" rear-end when throttle is applied, the rear tends to "squat." We've all seen that. With redux boxes it doesn't... Yeah... I think I read that before... how is that a bad thing for an offroad vehicle? Edu-ma-cate me?
remember when you were on the side of that hill and had to nearly sacrifice your leg to stop a rollover? when a swingaxle equipped vw's rear *rises* the positive camber kicks in..this is a very bad thing in many offroad situations..(mud maybe not, but i'm talking off roading not mudding)....the reduction boxes make the rear end rise up very noticeably when you throw the throttle to it...thus can contribute to the "wheel tuck" that could ruin your day on a steep embankment...
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