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5 rib transmission compared to 6 rib
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Roger Larsen
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PostPosted: Tue Oct 20, 2009 3:23 pm    Post subject: 5 rib transmission compared to 6 rib Reply with quote

Could anyone tell me the final gear ratio or a 5 rib transmission to the final gear ratio of the 76-79 6rib
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VDubTech
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PostPosted: Tue Oct 20, 2009 3:40 pm    Post subject: Reply with quote

Have you tried searching? I know this has been gone over before.
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Roger Larsen
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PostPosted: Tue Oct 20, 2009 4:04 pm    Post subject: Reply with quote

Yes I find info on the ring and pinion ratio but is that the same as the total final ratio in 4rth gear.
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PostPosted: Tue Oct 20, 2009 4:26 pm    Post subject: Reply with quote

There is some info right up there in the stickies, not sure if it has everything you are looking for...

http://www.thesamba.com/vw/forum/viewtopic.php?t=143138
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Roger Larsen
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PostPosted: Tue Oct 20, 2009 4:27 pm    Post subject: Reply with quote

The reason I want to know is I currently have a 73 westy with a 2000cc typ e4 dual carb engine with a 6 rib and am very happy with the performance gas mileage and all. I had a 72 bus that had and 002 with a 1700cc that was the was very poor in performance and millage. I have a project in the works that I have the chance to buy a 5 rib. I plan on the same engine 2 liter with dual carbs. Is this a half way compromise or what can I expect for performance and mileage. I currently get a constant 19mpg and can run 70 mph on the flat all day long with my westy.
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PostPosted: Tue Oct 20, 2009 4:48 pm    Post subject: Reply with quote

Thank you very much Dave ham-Very helpfull
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PostPosted: Tue Oct 20, 2009 4:53 pm    Post subject: Reply with quote

After searching transmission AND rib AND ratio in baywindow and following a link I found this on type2.com

091 Transmission Data
by David Schwarze


--------------------------------------------------------------------------------



"All T4 trannies have the same ratios in 1st, 2nd, and 3rd gears. The differences appear in 4th gear and final drive ratios. From '68 through chassis 213 2068 548 (mid '73) the 4th gear ratio was 0.82. From there on to '79 the 4th gear was 0.89."
I've seen that published too, but my experience didn't bear it out. I have a late '73 bus with chassis number well after the one above, but my 4th gear was .82. Didn't find out till it was too late. Sad

"The final drive ratio changed also, but at a different chassis #. From '68 through the end of the '73 model year (chassis 213 2300 001) the final drive was 5.375."
I think it's till the beginning of the '74 model year.

"Starting in 1974 chassis 214 2000 001) the final drive was changed to 4.867 through the end of the breadloaf series."
Not true - only '74 and '75 had the 4.867. 76-79 has 4.57 final drive (with the .89 4th gear).

"I happen now to own one of those oddball 0.89 4th gear, 5.375 final drive trannies."
I used to think that too. I'd be really suprised if you have one (I think they don't exist). Knowing the final drive, you could put it in gear, mark the shaft and prove me right or wrong by counting the number of turns on the input shaft vs. the output shafts.

"I also own a '78 tranny Tranny with the 0.82 4th and a 4.867 final drive, which allows 70+ cruising speeds, but quickly forces a drop in gears when you enter the mountains."
I think you have .89 4th and 4.57 final drive on that tranny.

"The advice I was seeking, since I am planning a cross country trip this June, is on which way to compromise. Should I seek the higher "flatland" speed across the midwest, or would the lower gearing of the late '73 tranny allow me to maintain speed in the mountains. The powerplant for this assemblage, BTW, is a '78 2L FI engine in a '73 body."
I still say keep the higher geared box. You'll do a lot more flat interstate than you will mountain passes. Here's a clip from a spreadsheet I made to help figure things out. The bastard transmission is a 78 case with the .88 4th gear and an oddball European ring and pinion (5.43/1) which combine for a serious stump puller. I used .88 for the 4th gear ratio in the later trans, but it may be .89. I've seen both in print and I haven't bothered to find out which it really is yet. Is it any wonder I don't trust anything I read about these tranny ratios anymore? The ideal trans is one I'm going to have built from my original '73 box with the .82 4th gear and the 4.86 ring and pinion from the '75 installed. I feel it will be a good compromise between freeway cruising speed and hill pulling in the lower gears.

Ring Final 4th gr 4th gear
and ratio ratio
Pinion Drive 0.88 0.82
----------------------------------------------
79 trans 32/7 4.57 4.02
75 trans 34/7 4.86 4.27
late 73 trans 43/8 5.38 4.41
bastard trans 38/7 5.43!! 4.78
ideal trans 34/7 4.86 3.98

And since that may have been a little confusing, here's another one that's a bit easier to understand. The first column is overall ratio in 4th gear, and the second column is how many RPMs you'll be turning at 60 mph with brand new 215/75R14 tires in back. Note that these tires are rather large. When I had 205/70's on the rear (which are comparable diameter to 195/75/14 btw) the RPMs were about 75-100 higher.
4th rpm@60mph
----------------------------------------------
79 trans 4.02 3326
75 trans 4.27 3534
late 73 trans 4.41 3644
bastard trans 4.78 3950
ideal trans 3.98 3293

Some of you are thinking that 3293 is a bit too low for the motor to be turning on the freeway, and you're probably right. It's okay though, because I'll be going back to smaller rear tires when I get this trans, which should put me at about 3375-3400 @ 60mph, which is exactly where I want to be (I'll normally be going 65ish anyway). One final thing to note is that putting bigger tires on the back of your bus isn't going to mess up the speedometer, because the speedometer is driven off of the front wheels.

The 091 trannies started in 76 in the US. At this time my best guess is that sometime in 74 they changed from 5.375 to 4.86, still in the 002 case. In 76 they started with the 4.57 and the 091 case. The 75 case was one year only, 002 number but with 091 style ribs on it.

This is one area where the Bentley appears to be a poor source of information. You really can't be sure what you've got until you open it up and look. You can just make an educated guess.
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PostPosted: Tue Oct 20, 2009 9:13 pm    Post subject: Reply with quote

Yes I have a double cab project I will be starting soon and when I travel I always seem to hit mountains. My Westy does great on flat land but when I hit the mountains we start to struggle. That is why I was considering maybe something besides the 091 but I do not want to go as low as the 002. Thanks for the help in doing my research.
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PostPosted: Wed Oct 21, 2009 8:28 am    Post subject: Reply with quote

Yes, all the internet gear ratio lists that I've seen have some inaccuracies.

I think that all 4.86 (7:34) R&Ps will be found in "Pyramid" (5-rib) cases, which first came out in '74 and ran through '75. I could be wrong, but I believe that the earliest '74 Pyramid cases had the 5.42 (7:38) R&P, which was the replacement ratio for the weaker 5.38 (8:43).

Although all U.S. import '76-'79 091s (6-rib) had the 4.57 (7:32) R&Ps, there were many European model 091s that had either 4.86 or 5.42. There were even a few with lower R&P ratios than these (as with the Swiss ambulance).

It's nearly impossible to have totally reliable ratio lists. I don't think that even the factory was perfect in their record keeping.
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PostPosted: Wed Oct 21, 2009 3:59 pm    Post subject: Reply with quote

I think my safest way to go will be to cough up the cash for a rebuilt 091.
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PostPosted: Wed Oct 21, 2009 4:34 pm    Post subject: Reply with quote

You might call Ken @ German Transaxle and pick his brain. He serviced my 5 rib a few months ago and had very favorable reviews of it compared with the 6 rib. Bend is surrounded by hills and mountains, which he feels the 5 rib handles better.

http://www.german-transaxle.com/contact-us/
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PostPosted: Sat Oct 24, 2009 6:07 pm    Post subject: Reply with quote

Roger,

The post above bearing my name IS very confusing and only parts of it were written by me. It's hard to make sense of it.

The answer to your original question is that the 091 has a 4.02 ratio and the 5-rib has 4.27. Both trannies have the same 4th gear (0.889), the only difference is that the 091 has a 32-tooth ring gear and the 5-rib has 34 teeth. If you go with the 5-rib you will reduce your speed by approximately 4mph at the same highway speed. Put another way, going with the 5-rib will raise your RPM by about 200 at 60mph.

-David
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PostPosted: Sat Oct 24, 2009 6:23 pm    Post subject: Reply with quote

Roger Larsen wrote:
Yes I have a double cab project I will be starting soon and when I travel I always seem to hit mountains. My Westy does great on flat land but when I hit the mountains we start to struggle. That is why I was considering maybe something besides the 091 but I do not want to go as low as the 002. Thanks for the help in doing my research.


I also wanted to comment on this particular statement. There is almost no difference in the overall ratio in 4th gear between the 002 and the 5-rib. Only about 1mph difference at 60mph. This is due to the fact that the 002 has a taller 4th and shorter R&P while the 5-rib has a shorter 4th and taller R&P. So if the 002 is too low on the highway for you, the 5-rib will likely also be too low.

No free lunch unfortunately, you are going to have to either choose to be better on the flats or better on the hills, or increase the power output of your engine. Smile Personally I would gear the bus for where you spend the majority of your time. Is it flat highway or hills? Which makes you angrier, downshifting on hills or having your speed limited on the flats? Oh, and remember that even with the 5-rib you will still probably be downshifting on bigger hills.

-David
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