Author Topic: Transmission skips 3rd  (Read 2781 times)

Steve.k

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Transmission skips 3rd
« on: August 14, 2018, 01:04:11 »
My 1971 automatic sometimes goes directly from 2nd to 4th.  It happens only once in a while and always in the first few minutes of a drive.   I’ve changed the ATF and filter and it still happens.   Otherwise it shifts pretty smoothly and at the right revs.   Ideas?

WRe

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Re: Transmission skips 3rd
« Reply #1 on: August 14, 2018, 07:02:56 »
Hi,
did you check the 3-position solenoid on the top of the transmission? Maybe it's stuck in one position (kick-down-position) when it's cold. It is accessible by removing an oval cover on the right side of the transmission tunnel forward of the passenger seat.
...WRe

Steve.k

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Re: Transmission skips 3rd
« Reply #2 on: August 14, 2018, 12:31:34 »
If it were stuck in the kick down position, wouldn’t it start in first gear?  When this skip happens, it always starts in second as usual.

Steve.k

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Re: Transmission skips 3rd
« Reply #3 on: August 21, 2018, 21:57:35 »
Any other ideas?   I had it in my mechanic’s shop last week to replace the engine mounts and asked him about it and he was scratching his head too.   
A generic, non specific vehicle google search has many posts mentioning a sticking valve body or solenoid.   Do either of these apply to Pagodas?
I assume this isn’t common?
« Last Edit: August 21, 2018, 22:10:28 by Steve.k »

Pawel66

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Re: Transmission skips 3rd
« Reply #4 on: August 22, 2018, 11:27:35 »
Steve, I am not a mechanic and cannot tell you what is the reason for your transmission skipping 3rd gear, but I was through my transmission battle and I can list what an amateur like me can do to eliminate the simple things:
- check the operation of the 3-way solenoid - does it go at all times to the position where it should be as per the gas pedal position?
- check the throttle switch operation (I am not saying it is the reason for 3rd gear skipped, but it should work correctly and is responsible partially for 3-way solenoid proper operation)
- replace the fluid and filter (which you did - what was the condition of the fluid? red? brown? smelling burnt or smellong nice as fluid? particles in?)
- check and adjust the fluid pressure in the transmission - maybe if it is on the edge of the range it will not shift when cold?

It is all there on the forum and in the Technical Manual, you just need to go point by point.

Again, not saying any of the above may be responsible for 3rd gear skipping and someone with experience may write: forget about all these, just get the tranny to the shop. But I would go through these points before that, driven by, stupid perhaps, hope that it will help.

And another question (a shot from the hip) - how is your speedo working? Erratic od nice and steady?
Pawel

280SL 1970 automatic 180G Silver
W128 220SE
W121 190SL
G-class

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Re: Transmission skips 3rd
« Reply #5 on: August 22, 2018, 14:17:55 »
My 1971 automatic sometimes goes directly from 2nd to 4th.  It happens only once in a while ......
My '70 and the '70 I used to own did the same thing. Also just once in a while. I look forward to hearing what others have to say. I have not read up on this issue for a while. I believe I read that we should make sure the bolts holding the valve body "above" the filter are torqued to spec when a fluid and filter change is done. I DID do this on both cars and they both still miss the 3rd gear once in a while.
Good Luck Steve !!
1970 280 SL Automatic, USA version, Grey-Blue (906G/906G), Blue leather (245)
1968 SS396 Camaro Convertible (owned since 1977 -- my first car :D)
1984 Porsche Euro Carrera coupe, LSD, SlateBlueMet/Blue
1998 BMW M-Rdstr Estoril Blue
1970 280 SL Automatic, Anthracite Grey-173G, Red Interior-132 - sold

Steve.k

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Re: Transmission skips 3rd
« Reply #6 on: August 22, 2018, 14:50:25 »
Pawel,

The old fluid was still nice and red, and the filter reasonable clean.  The PO maintained it well.  The speedo is dead solid, no issues whatsoever.  I'll have a look at the solenoid next time it's up on the hoist. 
How is the fluid pressure checked and adjusted?  - I'll search here for that one.


WRe

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Re: Transmission skips 3rd
« Reply #7 on: August 22, 2018, 17:24:04 »
Hi,
You will not see so much of the solenoid on a ramp, maybe you can feel it. You can see it working when you remove the oval cover on the right side of the transmission tunnel. Take the carpet a little bit aside and open it, only 2 screws, sometimes a little bit stuck of silocone or similar.
The modulator pressure adjustment is described in the workshop manual.
...WRe

Pawel66

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Re: Transmission skips 3rd
« Reply #8 on: August 22, 2018, 18:05:07 »
Yes, the modulator pressure check and adjustment is described in BBB and in Technical Manual. You need a gauge with banjo type connection for M8 screw if I remember correctly. You also may file down a piece of metal plate to make an adjustment tool - you will see.

Just take the values of pressure from BBB and convert them properly to whatever your gauge is showing. There are conversion mistakes in some posts on the forum.

Again - I have no idea if this eliminates your issue.

Quote from our Technical Manual:
"I finally got a call yesterday from the mechanic, and my car is done. Turns out that the transmission passing gear issue was, and many of the "clean up" and "sorting out" issues he discovered were matters of adjustments as I thought. In the initial case of the kickdown issue, 1st there were wiring problems, wires on the tranny were in the wrong place. 2nd, there was a broken wire on the harness at the relay. When those items were repaired, then the solenoid was able to work. Manually, they were able to get the kickdown to work; however the solenoid did not give enough travel in order to activate automatically. They tell me that the final resolution was linkage adjustment AND a bent "rod". When they straightened the bend rod (I think this is that the solenoid pushes on in the tranny) and adjusted the linkage, voila, it all works."

This bent rod was the rod through which the solenoid pushes on madulator lever. Its length can also be adjusted.
Pawel

280SL 1970 automatic 180G Silver
W128 220SE
W121 190SL
G-class

Steve.k

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Re: Transmission skips 3rd
« Reply #9 on: August 22, 2018, 18:30:17 »
Thanks Pawel, very helpful.