TheSamba.com :: View topic - What is this switch/sensor for on this transmission

Tue Aug 04, 2015 11:51 am

Hi everyone, I'm new to the hobby. I have procured a transmission that appears to be for 73-79 type 1 irs, the number on the case is AT 20 122. I have a 71 Super beetle and plan to marry this up to my 1641DP. What is the switch/sensor that is located on the drivers side of gearbox for? The switch on the pax side is for reverse lights. Will the driver side switch/sensor impact me using in my 71SB If not electrically hooked up? Is this gear box compatible? I plan to install new rear and front seal and use new nose cone adapter, change gear box oil, is there any other recommendations of things to do before I install this?

Thanks everyone Ken

Tue Aug 04, 2015 1:07 pm

extra switch is seat belt warning light

Tue Aug 04, 2015 1:31 pm

:shock: I thought that was reverse. but Ive never checked for sure.some also have one on the side on the hockey stick.witch I thought was for something along the lines of a netural safty or somethen goofey like oh say seat belts or tire pressure. but like I said..I havent checked as my bug dosent have either rev lights or front bumper.

Tue Aug 04, 2015 1:53 pm

That's the reverse light switch. There is no seat belt warning attached to the transmission. That's attached to the ignition and the belt buckle.

Tue Aug 04, 2015 2:19 pm

Single side cover? nice. Clean it and paint it.

Tue Aug 04, 2015 2:44 pm

http://www.thesamba.com/vw/forum/viewtopic.php?t=567732&view=previous
seat belt warning :wink:

Tue Aug 04, 2015 5:01 pm

Switch on nose cone (lower left) in this image is backup light switch...

Dale

Tue Aug 04, 2015 5:43 pm

Dale M. wrote: Switch on nose cone (lower left) in this image is backup light switch...

Dale
Op said driver side of car, and that switch is for the seat belt buzzer. Has one terminal, you can leave it unattached.

Tue Aug 04, 2015 6:06 pm

Thanks to all who responded……. This particular gear box apparently has a different gear ratio, 3.875 vs what I think I presently have 4.125. Can't wait to try er out.

Tue Aug 04, 2015 6:17 pm

RideAllieRide wrote:

I don't have anything worthwhile to contribute, but I just can't help cringing a little whenever I see a gearbox removed with a cutting torch. For the love of Pete, it's only two more bolts. Do they have to destroy the whole car for that?

Sorry, I'll stop whining now.

Tue Aug 04, 2015 6:45 pm

RideAllieRide wrote: Thanks to all who responded……. This particular gear box apparently has a different gear ratio, 3.875 vs what I think I presently have 4.125. Can't wait to try er out.

That trans does have a 3.88 r/p combined with the fourth ratio of .94 you have a final of 3.65, and your current box has a 4.12 with a .89 fourth gear which nets a 3.66 final drive. Your ratio in fourth gear is basically the same on both trans. And the newer one is prone to having reverse bad. Sorry, didn't mean to pee in your oatmeal, however that is one of the best boxes to build for irs applications

Fri Aug 07, 2015 2:29 pm

mcmscott, thanks for the ratio info. Would be disappointing for sure if reverse is gone. I have no history of gear box, bought as you see it.

Fri Aug 07, 2015 3:13 pm

Just tossing this out in case the neutral idea doesn't pan out when checking it out electrically. Try 4th.

On some VW models and some years, VW (and others) used "transmission controlled spark advance" or TCS, which was a fancy way of saying you had no advance until you were in top gear. Atrocious idea that killed power, mileage, and engines.

Any chance this switch is tied to top gear, not neutral for the seat belt?

Fri Aug 07, 2015 3:21 pm

KTPhil wrote: Just tossing this out in case the neutral idea doesn't pan out when checking it out electrically. Try 4th.

On some VE models and some years, VW (and others) used "transmission controlled spark advance" or TCS, which was a fancy way of saying you had no advance until you were in top gear. Atrocious idea that killed power, mileage, and engines.

Any chance this switch is tied to top gear, not neutral for the seat belt?

No, it is for the seat buzzer. I build vw trans daily, trust me.

Fri Aug 07, 2015 5:34 pm

RideAllieRide wrote: mcmscott, thanks for the ratio info. Would be disappointing for sure if reverse is gone. I have no history of gear box, bought as you see it.
You can see reverse through the fill plug hole. The teeth of the gear are straight, not helical. If they have any type of folding/laying over wear to them, and aren't perfectly straight, the trans will pop out of reverse. Bolt on a spare shift rod coupler, and shift it into the gears while turning it over. That's about the only things you can do to check the condition of an unknown gearbox.

Fri Aug 07, 2015 7:04 pm

[email protected] wrote: RideAllieRide wrote: mcmscott, thanks for the ratio info. Would be disappointing for sure if reverse is gone. I have no history of gear box, bought as you see it.
You can see reverse through the fill plug hole. The teeth of the gear are straight, not helical. If they have any type of folding/laying over wear to them, and aren't perfectly straight, the trans will pop out of reverse. Bolt on a spare shift rod coupler, and shift it into the gears while turning it over. That's about the only things you can do to check the condition of an unknown gearbox.

No you cannot see reverse thru the fill hole, you can see the 1-2 operating sleeve that engages with the reverse idler. If the idler are worn you may not see it in the slider

Fri Aug 07, 2015 7:11 pm

mcmscott wrote: [email protected] wrote: RideAllieRide wrote: mcmscott, thanks for the ratio info. Would be disappointing for sure if reverse is gone. I have no history of gear box, bought as you see it.
You can see reverse through the fill plug hole. The teeth of the gear are straight, not helical. If they have any type of folding/laying over wear to them, and aren't perfectly straight, the trans will pop out of reverse. Bolt on a spare shift rod coupler, and shift it into the gears while turning it over. That's about the only things you can do to check the condition of an unknown gearbox.

If the idler are worn you may not see it in the slider
True.

If the gear teeth on the slider are good, it doesn't mean reverse is good. But if the gear teeth on the OD of the slider are bad, reverse is bad.

Sat Aug 08, 2015 6:36 am

Yeah, you're right, I guess technically you're only seeing one of the four gears that make up reverse, and not the one little gear most commonly refered to as the reverse gear that usually goes bad. Like Bruce mentioned, if the large half/slider is bad, the trans definately isn't going to function properly as is. I don't want to discourage the OP, but I haven't taken apart too many transaxles with reverse gears that would have functioned properly.

Tue Aug 11, 2015 10:13 am

No discouragement taken, if it doesn't function it will be a learning/teaching platform for me and local club members then. Thanks for all your input!

Tue Apr 06, 2021 8:59 pm

mcmscott wrote: Dale M. wrote: Switch on nose cone (lower left) in this image is backup light switch...

Dale
Op said driver side of car, and that switch is for the seat belt buzzer. Has one terminal, you can leave it unattached.

Last Friday I ran the car for about 30mins. Got home and noticed that there was a sound like oil boiling. I checked my engine dipstick and the oil wasn’t hot. I couldn’t find the source of that boiling sound. The next morning I took out the car for a drive on my return back I noticed a pool of clean oil and a spring and sensor. Oh my garage floor. At first I thought it was engine oil then I smelled transmission oil. I finally realized what happened the tranny oil go so hot that it made the reverse light sensor come off the tyranny . I jacked up the car and tranny oil came out where the sensor was.

Why did my transmission overheat? There’s no metal in the oil and it shifts fine, maybe my tranny oil was low? The transmission is a pro street.

I just installed a fresh 1600 w 34 icts the engine before no heating issue,

Any advice thanks