Author Topic: 250SL Gearbox problem (Read 10389 times)

n/a · « **on:** January 29, 2007, 11:47:20 »

Need advice about long term problem with gearbox.
Gears are not engaging in the correct speed, also snatchy.
There is sporadic clanging and rumbelling with a bang in lower gear.
Any knowledge of recondition gerabox for sale or reasons for this occuring problem.
Thank you,
Tony

paulr · « **Reply #1 on:** January 29, 2007, 13:31:27 »

Hi Tony

I can only sympathise as in my experience this is an annoying and tricky problem to solve. Your symptoms describe my gearbox almost exactly and it's taken quite a time to get it better, but not cure.
The first thing I understand is that these gearboxes were designed to be used with a much larger engine whose torque would smooth out the sometimes rough gear changes. This doesn't mean of course that that is Ok but it might help explain it's rudeness sometimes.
I have a 280 which has had the gearbox rebuilt, by monkeys actually ( this was a car warranty issue ), so I have to assume that some of the things they did were right. It has been back in several times and finally the guys at Roger Edwards in London have tweeked it and it's somewhat better, so a rebuild isn't necessarily going to do it either.
I am, as we speak having the rubbers replaced in the rear axle to both improve ride height and level but most importantly to help with that sometime spine shattering final gear change when stopping when it feels the rear of the car may join you up front.
In short Tony, I would see if you can find someone to 'holistically' view your car and tinker little and often and to sometimes do what may seem unrelated at the time to ease it towards a decent gearbox and drive, This is the way that my circumstances have taken me and although slower than I would like, does seem to be working. I think part of it is adjusting my expectations.
I know this doesn't answer your question but it might help you feel less alone. Others will have more experienced views...which I will be keen to hear too.

good luck.

paulr

Cees Klumper · « **Reply #2 on:** January 29, 2007, 16:42:34 »

The shifting on my 280 SL automatic is usually very smooth; only rarely is there a bit of a jerk, and then modestly so. There have been many posts about this; I believe much can be done to smoothen out the shifting. Probably worthwhile to do a search on this.

Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic

rwmastel · « **Reply #3 on:** January 30, 2007, 22:56:49 »

quote:
Originally posted by paulr

I am, as we speak having the rubbers replaced in the rear axle to both improve ride height and level but most importantly to help with that sometime spine shattering final gear change when stopping when it feels the rear of the car may join you up front.

TONY,
This item could help one of your automatic transmission issues.

PAUL,
Don't spend thousands at Roger Edwards on a rear axle rubber replacement just to fix that last hard down shift!!! Just have them adjust the venturi flap (intake manifold flap). It can often be incorrectly used as an idle adjustment, but that messes up the vacuum in the intake manifold, which messes up the transmission!! It's a 5 minute job at most.

Check out the Linkage Tour:
http://index.php?topic=5003

See post by JA17 here:
http://index.php?topic=6091

Another explaination:
http://index.php?topic=4788

If you use the Search tool, you'll find more.

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both tops
1994 E420

paulr · « **Reply #4 on:** January 31, 2007, 00:54:31 »

ROD

I'm not, this is part of a much bigger project that involves the rear axle / ride hieght / rubbers /rude gear changes etc.

I will pass on the comments about the venturi too.

thanks a lot

quote:
Originally posted by rwmastel

quote:
Originally posted by paulr

I am, as we speak having the rubbers replaced in the rear axle to both improve ride height and level but most importantly to help with that sometime spine shattering final gear change when stopping when it feels the rear of the car may join you up front.
TONY,
This item could help one of your automatic transmission issues.

PAUL,
Don't spend thousands at Roger Edwards on a rear axle rubber replacement just to fix that last hard down shift!!! Just have them adjust the venturi flap (intake manifold flap). It can often be incorrectly used as an idle adjustment, but that messes up the vacuum in the intake manifold, which messes up the transmission!! It's a 5 minute job at most.

Check out the Linkage Tour:
http://index.php?topic=5003

See post by JA17 here:
http://index.php?topic=6091

Another explaination:
http://index.php?topic=4788

If you use the Search tool, you'll find more.

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both tops
1994 E420

paulr

hands_aus · « **Reply #5 on:** January 31, 2007, 05:35:00 »

The adjustment of the inlet manifold is only one of the adjustments needed to get the electrical side of the auto transmission working correctly.
The idle switch on the inlet manifold may not work correctly if the vacuum is not correct because of an incorrectly adjusted venturi valve.

Normally the idle switch causes the 3 position solenoid on the auto transmission to be in the correct position when slowing down and has a direct affect on the modulating pressure diaphragm and consequently on the modulating pressure.
This has a direct affect on the harshness of the final down shift.

This topic has been discussed many times and a search of the site will surely be of help.

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

JPMOSE · « **Reply #6 on:** January 31, 2007, 08:30:58 »

Also note the Venturi Flap can require cleaning (along with the chamber housing it). Mine had a build-up of crud and flap wouldn't quite close completely. Hence, the idle micro switch wasn't engaging and I had a hard downshift. I removed the rubber hose leading to the air cleaner and sprayed Gumout back on to the flap and chamber but ultimately I had to remove the housing and manually clean up inside. I think the fumes entering in off the valve cover pipe built up resin over time. Along with hard down shifting, this micro switch not engaging also prevents operation of the Fuel Cutoff Solenoid on the back in the injector pump (US Emissions Only - 1968 model year and later).

Best Regards,

J. P. Mose
1968 250SL
1987 560SL

Ben · « **Reply #7 on:** February 02, 2007, 09:34:44 »

I think what paulr is talking about, is that if the rear exles bushes are badly worn, the entire axle shudders on down shift and this reverberates through the car, feeling very nastly indeed !

I have this with my W111 at the moment and I am installing new bushings tomorrow!

Regards,
Ben in Ireland.
'64 230SL 4sp.

paulr · « **Reply #8 on:** February 02, 2007, 13:40:48 »

Ben

you're absolutely right... I was only offering this as part of the answer to my particular car. I will let you know how the car feels. I am nearly done with all those niggling things.

My car spent some time in your beautiful Country at Heeneys.

kind regards

paulr

quote:
Originally posted by Ben

I think what paulr is talking about, is that if the rear exles bushes are badly worn, the entire axle shudders on down shift and this reverberates through the car, feeling very nastly indeed !

I have this with my W111 at the moment and I am installing new bushings tomorrow!

Regards,
Ben in Ireland.
'64 230SL 4sp.

paulr
lovely 1970 280 SL

J. Huber · « **Reply #9 on:** February 02, 2007, 17:56:37 »

I may be getting in over my head but I decided to try something today. My car generally shifts okay -- it seems like on heavier acceleration, 2-3 is almost not clunky, and 3-4 is about perfect. When I go slower, however, 2 to 3 feels like somebody kicked me in the hindquarters...And actually it has gotten worse lately.

So, I took a look at my butterfly valve in the venturi and like JP Moses' mine had some crud in there. But overall, it seemed to shut all the way with out sticking. My P idle stays at about 950-1000. However...I have some play on the metal piece that hits the stopper. If I manually push it to where it is hitting the stop, the idle goes down to about 750. I tried to clean-up the hinges all around but still have this play. Is this play normal? I wonder if this play leads to the occasional higher idle and more clunky shifts. Any thoughts?
Thanks.

James
63 230SL

rwmastel · « **Reply #10 on:** February 02, 2007, 20:33:35 »

quote:
Originally posted by J. Huber

My P idle stays at about 950-1000. However...I have some play on the metal piece that hits the stopper. If I manually push it to where it is hitting the stop, the idle goes down to about 750. I tried to clean-up the hinges all around but still have this play. Is this play normal?

James,

Hi. I don't know what a "P idle" is, but regarding all the throttle linkages, the less play the better. No play is best.

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both tops
1994 E420

J. Huber · « **Reply #11 on:** February 02, 2007, 21:55:22 »

Hi Rodd, I guess that sounds a little funny. Not talking bladder control -- I meant the idle while in Park...

James
63 230SL

hands_aus · « **Reply #12 on:** February 03, 2007, 14:11:39 »

some earlier models have on the throttle linkage a damper that might hold the venturi open enough to increase idle rpms.

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

J. Huber · « **Reply #13 on:** February 03, 2007, 14:41:38 »

I just figured out that the stop at the venturi coincides with the Constant Speed Solenoid. Is that what you mean Bob? It seems they hit at the same time. I may have cured the play by adjusting that a scoach. Idling fairly steady (still high at 850-900 cold but at least its constant) -- time for a testdrive...

James
63 230SL

hands_aus · « **Reply #14 on:** February 04, 2007, 03:13:01 »

quote:
Originally posted by J. Huber

I just figured out that the stop at the venturi coincides with the Constant Speed Solenoid. Is that what you mean Bob? It seems they hit at the same time. I may have cured the play by adjusting that a scoach. Idling fairly steady (still high at 850-900 cold but at least its constant) -- time for a testdrive...

James
63 230SL

Hey James,
Maybe on manuals only?
The in-gear idling speed ( CSS ) should be adjusted after setting up the rest of the linkages.

Generally idle speed is around 800 rpm

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

ja17 · « **Reply #15 on:** February 04, 2007, 08:24:49 »

Hello James,

It sounds like you have a linkage problem or a linkage input problem. Something is not allowing your linkage to fully return to stop. Your harsh shifting should go away when you solve this issue.

To troubleshoot your fast idle problem, let the engine idle next disconnect the linkage rod going down from the cross over rod to the block pivot, disconnect the linkage at the venturi, disconnect the linkage at the injection pump. Start hooking them back up one at a time with the engine idling. Start at the block pivot linkage, next the injection pump and finnally the venturi. If connection of a linkage causes idle to increase you have a problem on that branch. Check to make sure a linkage input like the constant speed solenoid is not holding the linkage open slightly. Sometimes the linkage rod going to the block pivot is too long and not allowing the accelerator linkage to return always. Sometimes the venturi linkage and the injection pump linkages are not in sync and these units are not fully against their stops at idle.

Also realize that the transmission venturi switch is adjustable. By loosening its fastening screws (two 5mm allens) and rotating the switch counterclockwise you actvate the three position solenoid on the transmission to lower pressure sooner. Use this as last resort, look for the cause of the fast idle first and this will most likely cure the harsh shifting. Keep us up to date.

Joe Alexander
Blacklick, Ohio

J. Huber · « **Reply #16 on:** February 04, 2007, 15:59:17 »

Well, some positive news to report. Joe, I did some testing as you prescribed. First, however, I needed a translator to understand the various pieces... So I turned to George Davis's great write-up on Basic Linkage Adjustment (on Pagoda113). It all began to make sense. I removed the rods and cleaned and regreased the balls. I also measured the one on the pump side -- it matched the magic number 233 just right. As I started to reinstall each rod per Joe's idea, there was no change in idle -- until the last connection at the venturi idle stop. I decided to shorten that rod two turns of a ballsocket, and it dropped the idle down to just above in-gear idle speed. Still could go a bit more maybee but an improvement...

On to the test drive: well, sure enough, the shift on partial throttle from 2-3 is much better. Before it was a clunk -- now, it is more like a shudder? -- I think hear it more than I feel it. On accelaration -- everything shifts "like butta"... So I am generally pleased. Thanks guys.

Oh, one last question: In GD's write-up he mentions a tune-up tach is more accurate than the dash -- so I bought one! but it has horrible directions. Anybody want to help me on this one? It is a Tach-Dwell bugger with a green clamp and a black one... Just not sure how to hook it up...

James
63 230SL

ja17 · « **Reply #17 on:** February 04, 2007, 17:26:10 »

Hello James,

It sounds like your on track now. If you still need some linkage information try;

http://sl113.org/forums/index.php?topic=5003+tour

Joe Alexander
Blacklick, Ohio

Ben · « **Reply #18 on:** February 05, 2007, 07:36:23 »

Hi James, glad to hear you are getting places !

quote:
Oh, one last question: In GD's write-up he mentions a tune-up tach is more accurate than the dash -- so I bought one! but it has horrible directions. Anybody want to help me on this one? It is a Tach-Dwell bugger with a green clamp and a black one... Just not sure how to hook it up...

....usually you have 4 connecytions, negative(balck),positive(red) and the green wire goes to the wire from the coil to the points. Then you have a clamp type connector for plug lead number 1 !

Hope that helps !

Regards,
Ben in Ireland.
'64 230SL 4sp.

J. Huber · « **Reply #19 on:** February 06, 2007, 17:49:05 »

Thanks Ben. I finally figured out the tach meter. It does only have two wires: black goes to - battery and green that goes to the distributor side of coil...seems to work fine. However - using the dwell side of the meter -- it is showing my dwell at 27 degrees. I kept retesting because I was expecting the high 30s...but its 27. Anyone care to tell me what this means?

James
63 230SL

hands_aus · « **Reply #20 on:** February 07, 2007, 06:23:37 »

quote:
Originally posted by J. Huber

Thanks Ben. I finally figured out the tach meter. It does only have two wires: black goes to - battery and green that goes to the distributor side of coil...seems to work fine. However - using the dwell side of the meter -- it is showing my dwell at 27 degrees. I kept retesting because I was expecting the high 30s...but its 27. Anyone care to tell me what this means?

James
63 230SL

Hey James,
A small dwell angle with points installed usually means that the rubbing block on the points has worn down.
How long since you installed new points?
Normal dwell is in the range 38 +3 -1

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

J. Huber · « **Reply #21 on:** February 07, 2007, 12:57:01 »

Thanks Bob. Yes, its been a while for points. Car has held up so I have held out...But points & plugs just catapulted to the top of the list!

So now that I have taken this thing over -- Hey Tony -- have you had any luck with your issues?

James
63 230SL

rwmastel · « **Reply #22 on:** February 07, 2007, 22:15:31 »

:?: Is Tony ever going to check back on his post :?:

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both tops
1994 E420

Ben · « **Reply #23 on:** February 08, 2007, 04:33:37 »

James, a small dwell reading would mean that the points gap is too large, and vice versa !

Usually when the points block wears down the gap closes up !

Regards,
Ben in Ireland.
'64 230SL 4sp.

Naj ✝︎ · « **Reply #24 on:** February 08, 2007, 04:50:47 »

Hey, James,
Tinkering with the points also changes the ign timing, so should recheck after setting the points gap.
Now, if you had pointless...... :mrgreen:

naj

68 280SL

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