3 rib trans help
- 69yellowbug
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- Joined: Sat May 23, 2015 8:37 pm
3 rib trans help
Ok I have a 3 rib trans and all the numbers I can find are the 002.301.103 number and from what I can find that's the base trans number and then their is the other stamped number that I cant find anything on C006 3850. I want to find out the gear ratios of all the gears to see if it is what I want for the type of driving I do.
- Henryhoehandle
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Re: 3 rib trans help
A pic would help. However, almost all were(1st through 4th)- 3:80, 2:06, 1:26, .82. with a R&P of 5:38
There were some diesel 3ribs that were different (5:42 r&P)and there also may be an oddball here and there as well. Others here may shed light on those....
There were some diesel 3ribs that were different (5:42 r&P)and there also may be an oddball here and there as well. Others here may shed light on those....
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Re: 3 rib trans help
Serial # C 0063850 should be a 1968 (confirm this by the 6 acorn nuts surrounding the drive flange, all later 3 ribs had 2 phillips screws fore and aft of the flanges). "CK" rather than just "C" in the serial # would be 1969 or later still w/1600 motor, "CK" would be the latest of the 3 rib trannys which came with 1700 motors. This applies to U.S. vans. Henry is correct on ratios.
- 69yellowbug
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Re: 3 rib trans help
It has acorn nuts on both side covers.
- 69yellowbug
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Re: 3 rib trans help
Ok I compaired my trans which is an AM 3:78, 2:06, 1:26, :93 RP 4:375 to the 3 rib 3:80, 2:06, 1:26, :82, RP 5:38 but get confused with the numbers. What will I see?
- Marc
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Re: 3 rib trans help
See? As in what RPM difference there'd be between the two?69yellowbug wrote:Ok I compaired my trans which is an AM 3:78, 2:06, 1:26, :93 RP 4:375 to the 3 rib 3:80, 2:06, 1:26, :82, RP 5:38 but get confused with the numbers. What will I see?
First, it's commonplace for VW guys to refer to the tooth count when talking about R&P sets, while expressing the other gears simply by their ratio (unless the subject is comparing the strength of various available gearsets)...35:8=4.375 (not 4:375) and 43:8=5.375.
Multiply the R&P ratio by the gear ratio to get a number representative of the overall ("final") ratio for each trans, then divide those to see the percentage difference.
Since first through third are the same in these two boxes, you can simply compare R&P ratios: 5.375÷4.375=1.228 ....engine RPM at a given roadspeed would be 23% higher with the 3-rib.
For fourth it's (5.375x.82)÷(4.375x.93) which is 4.41÷4.07=1.084, so there'd only be about 8% change.
The "gap" between third and fourth is reduced from ~53% to ~35%. With the AM, if you shift to fourth when you hit 4000 in third the RPM drops to 2950; with the 3-rib it'd be 2600.
Unless it was replaced with a 38:7 set, the R&P will be a 43:8 - arguably the weakest Bus set ever made, although probably adequate for a lighter vehicle if it isn't chewed up already.
- 69yellowbug
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Re: 3 rib trans help
It's going in a baja bug that I like to fairly slow ride the thing I don't like about the AM is when I shift from 3rd to 4th the rpm are way too low and I'm out of power to accelerate. Am I just not shifting at a high enough RPM to keep up? I have open exhaust and shift at 3000 rpm and it sounds loud so I 5hink I need to shift.
- Henryhoehandle
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Re: 3 rib trans help
You could swap out 4th gear for a .88 (or whatever you need) ratio... The "acorn nut" style trans is the earliest of the IRS type 2 transmissions I believe. The way the pinion shaft is setup is JUNK, imo, however since it is working now, and if you treat it tenderly then it may hold up for awhile. It should have the ratios I stated above in my first post. You can go to www.weddleindustries.com and use their gear calculator and figure out exactly what you need.
- Marc
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Re: 3 rib trans help
A stock ACVW motor doesn't reach its peak HP until about 4400 RPM (and really shouldn't be subjected to a heavy load below ~2000 to keep from beating up the case at the mains) ...so you're definitely "short-shifting" at 3000. That's about the ideal RPM for most motors, they can run there all day.69yellowbug wrote:...I have open exhaust and shift at 3000 rpm and it sounds loud so I 5hink I need to shift.
- 69yellowbug
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Re: 3 rib trans help
I thought so but with the open exhaust it sounds like im red lineing it.