Author Topic: Intro & Shifter linkage Gear selector Issue 79 300SD  (Read 361 times)

Squiggle Dog

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Re: Intro & Shifter linkage Gear selector Issue 79 300SD
« Reply #15 on: 26 November 2018, 01:02 PM »
Good and bad news, I see. Try this; with the shift rod disconnected at the transmission side, move the lever on the transmission to the park position (all the way toward the rear of the car, I think). If you don't hear and feel the parking pawl engage and the car is still able to roll, then the parking pawl likely got damaged.

I think you can repair or replace the parking pawl by removing the yoke and then the rear section of the transmission. I don't think you necessarily have to have the transmission removed in order to do this, but everything needs to be kept surgically clean when going back together.
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1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
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Jjutzy

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Re: Intro & Shifter linkage Gear selector Issue 79 300SD
« Reply #16 on: 03 December 2018, 02:14 AM »
It’s been a while. I’ve been working some long hours and extra shifts ramping up for Christmas.

Anyway, just got out from under the car. I’ve got everything besides Park. Definitely thinking that I’m going to have to repair the Pawl. Is this a part I should be able to source new? I have had no luck finding the part number nor looking it up as a parking pawl. Would anyone happen to know the part number? I’d really like to have the replacement part on hand before I rip into that tail cone. As it is, I’m going to see if I can rig up the parking brake so I can at least get it in to get smogged and licensed. In the meantime, if I could get the parts on order to repair the Pawl, I’d be happy. I may have a line on an entire transmission, but prefer not to do that if I can just replace the broken part...

Thanks,
John
1979 300 SD 348,000+ Miles

Alec300SD

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Re: Intro & Shifter linkage Gear selector Issue 79 300SD
« Reply #17 on: 03 December 2018, 07:32 AM »
Parking Pawl 1979 300SD:  1152780221

Free shipping with promo code: "BENZWORLD 2017"
at https://www.mboemparts.com/oem-parts/mercedes-benz-pawl-1152780221
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daantjie

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Re: Intro & Shifter linkage Gear selector Issue 79 300SD
« Reply #18 on: 03 December 2018, 07:42 AM »
Some advice which help me a lot when I had a similar issue with the 6.9...Make double sure ALL your bushings on the shifter mechanism is in perfect shape.  From memory there is a nylon bushing where the shifter "down rod" (sorry not sure of the tech term) connects to the actuating rod.  Then also, pull the whole shifter mechanism, and you will see there are 2 large plastic bushings (probably well worn or gone) on the lateral section, plus also there are 2 tiny plastic bushings which orientate the spring mechanism on the shaft.  These bushings are super cheap and easy to replace.
This might not be the issue, but they are easy to replace and make a huge difference in the feel of the shifter as well as ensure you engage the notches in the gate properly, with no flapping of the handle.
But yes, if your pawl is buggered, then this is a fairly large job.  On the 6.9 at least the pawl is reenforced to my knowledge, I am guessing due to increased weight of that monster v8 ;)
Daniel
1977 450 SEL 6.9 - Astralsilber

Jjutzy

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Re: Intro & Shifter linkage Gear selector Issue 79 300SD
« Reply #19 on: 03 December 2018, 08:47 AM »
Can I drop the nose cone without dropping the entire transmission?

Also, after reading up a bit on this, it may not be as simple as just replacing the Pawl? Chances are, it may still be good, but the plastic arm that moves it into and out of position may be what broke? Any input from any of you who have been through this before?

Thanks,
John
1979 300 SD 348,000+ Miles

Squiggle Dog

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Re: Intro & Shifter linkage Gear selector Issue 79 300SD
« Reply #20 on: 03 December 2018, 10:46 AM »
This might help: https://cardiagn.com/atsg-mercedes-722-1-722-2-transaxle-service-manual-pdf/ . Also, it may not be possible to tell what or how many parts are affected without taking off the rear section of the transmission, but it should be able to be done while installed in the vehicle.
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1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
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UTn_boy

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Re: Intro & Shifter linkage Gear selector Issue 79 300SD
« Reply #21 on: 04 December 2018, 07:03 PM »
Can I drop the nose cone without dropping the entire transmission?

Also, after reading up a bit on this, it may not be as simple as just replacing the Pawl? Chances are, it may still be good, but the plastic arm that moves it into and out of position may be what broke? Any input from any of you who have been through this before?

Thanks,
John

John, there are no plastic linkages that move the parking pawl into or out of the actual parking gear.  It's all metal linkage.  In the picture below, take note of the parts highlighted in a blue square.  Number 460 is the actual metal linkage, number 457 is your parking pawl, and number 452 is the parking gear.  The parking gear is coupled to the output shaft via splines.  It's not unheard of for a parking pawl or parking gear to sheer and become damaged, but it's highly unlikely, especially since these transmissions have a hydraulic interlock to disallow engagement of park at speeds above 10-12 miles per hour. 

If either the parking pawl or parking gear are, in fact, damaged, then as Daniel and Scott have mentioned the repair can be done with the transmission still attached to the engine.  However......you will need a special socket to remove the slotted nut that holds the yoke on to the output shaft, (After you disconnect the driveshaft) ,and you'll also need a special tool to remove the screw that holds the secondary oil pump in (item number 599 in the picture).  A self made tool can be made for the secondary pump screw, but if the original slotted nut is still on the yoke of the output shaft you'll have to either buy the special socket or say a few Hail Mary's and hope it'll come loose with a hammer and a chisel.  If the hammer and chisel are used for removal, then you'll have to buy a new nut, which is thankfully now a nut that takes a regular deep well socket for tightening and removal.

In more unusual circumstances, broken/torn motor mounts and a torn transmission mount can also cause your problem.  When the mounts break, the whole drive train can shift forward, backward or sideways, and will throw the geometry off so much that shift linkages will not fully engage in any of the gears.....most notably Park.  Though, if the car is still starting in Park or Neutral, then the aforementioned is negated. 

Also, when an event occurs, such as a flex disc letting loose, the driveshaft can also break the rear housing on the transmission.  This housing is designed to break in the event of an impact.  Many rear housings have been damaged/broken due to the driveshaft coming loose from the flex disc.  Consequently, if the rear housing is broken this can also alter the geometry of the shift linkages.  If a replacement exhaust has been fitted incorrectly, the exhaust can pull back on or push forward on the drive train when one of the mounts comes loose or breaks....again altering the linkage geometry. 

Since you've already replaced the shift gate housing and the actual shift linkage, then we can rule those out.  This leaves motor mounts, transmission mount, rear housing, and even the bracket that the sift linkage attaches to as suspect items of interest.  And don't forget that the actual transmission tunnel (where the shift gate housing screws to) can also become distorted causing a misalignment in the linkages.  Obviously, the distortion can come from the driveshaft striking the transmission tunnel sheet metal.  You'll literally have to look at everything to determine what's causing the misalignment.  Even things that you wouldn't think to check.  :) 

« Last Edit: 04 December 2018, 11:22 PM by UTn_boy »
1966 250se coupe`, black/dark green leather
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Jjutzy

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Re: Intro & Shifter linkage Gear selector Issue 79 300SD
« Reply #22 on: 05 December 2018, 01:34 AM »
Can I drop the nose cone without dropping the entire transmission?

Also, after reading up a bit on this, it may not be as simple as just replacing the Pawl? Chances are, it may still be good, but the plastic arm that moves it into and out of position may be what broke? Any input from any of you who have been through this before?

Thanks,
John

John, there are no plastic linkages that move the parking pawl into or out of the actual parking gear.  It's all metal linkage.  In the picture below, take note of the parts highlighted in a blue square.  Number 460 is the actual metal linkage, number 457 is your parking pawl, and number 452 is the parking gear.  The parking gear is coupled to the output shaft via splines.  It's not unheard of for a parking pawl or parking gear to sheer and become damaged, but it's highly unlikely, especially since these transmissions have a hydraulic interlock to disallow engagement of park at speeds above 10-12 miles per hour. 

If either the parking pawl or parking gear are, in fact, damaged, then as Daniel and Scott have mentioned the repair can be done with the transmission still attached to the engine.  However......you will need a special socket to remove the slotted nut that holds the yoke on to the output shaft, (After you disconnect the driveshaft) ,and you'll also need a special tool to remove the screw that holds the secondary oil pump in (item number 599 in the picture).  A self made tool can be made for the secondary pump screw, but if the original slotted nut is still on the yoke of the output shaft you'll have to either buy the special socket or say a few Hail Mary's and hope it'll come loose with a hammer and a chisel.  If the hammer and chisel are used for removal, then you'll have to buy a new nut, which is thankfully now a nut that takes a regular deep well socket for tightening and removal.

In more unusual circumstances, broken/torn motor mounts and a torn transmission mount can also cause your problem.  When the mounts break, the whole drive train can shift forward, backward or sideways, and will throw the geometry off so much that shift linkages will not fully engage in any of the gears.....most notably Park.  Though, if the car is still starting in Park or Neutral, then the aforementioned is negated. 

Also, when an event occurs, such as a flex disc letting loose, the driveshaft can also break the rear housing on the transmission.  This housing is designed to break in the event of an impact.  Many rear housings have been damaged/broken due to the driveshaft coming loose from the flex disc.  Consequently, if the rear housing is broken this can also alter the geometry of the shift linkages.  If a replacement exhaust has been fitted incorrectly, the exhaust can pull back on or push forward on the drive train when one of the mounts comes loose or breaks....again altering the linkage geometry. 

Since you've already replaced the shift gate housing and the actual shift linkage, then we can rule those out.  This leaves motor mounts, transmission mount, rear housing, and even the bracket that the sift linkage attaches to as suspect items of interest.  And don't forget that the actual transmission tunnel (where the shift gate housing screws to) can also become distorted causing a misalignment in the linkages.  Obviously, the distortion can come from the driveshaft striking the transmission tunnel sheet metal.  You'll literally have to look at everything to determine what's causing the misalignment.  Even things that you wouldn't think to check.  :)

Thank you for this excellent input.

So, I can shift into all gears. I replaced the flex disc and I drove the car around the block, testing all gears, including reverse. Transmission seems fine, other than the fact that Park will not engage. I have crawled under the vehicle, removed the linkage, and shifted the transmission, manually, into Park. The Pawl is definitely not engaging.

Question: Could a misalignment keep me from being able to engage park at the side of the transmission? One of the tabs is broken on the back of the of the lever that attaches the linakage to the transmission (there are two tabs on this piece). I’m assuming that that piece only serves to engage/disengage the neutral safety switch, and would not have anything to do with the parking pawl?

I’m assuming I can buy the tools from mercedessource.com or one of the other parts houses.

My gut tells me that this is a parking pawl. My gut has often been wrong in my years as a shade tree mechanic... 🤦‍♂️
1979 300 SD 348,000+ Miles

UTn_boy

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Re: Intro & Shifter linkage Gear selector Issue 79 300SD
« Reply #23 on: 05 December 2018, 02:53 AM »
Well, if you detached the linkage, and pulled the shift lever bracket all the way to the rear while spinning the output shaft yoke and it didn't stop, then your assumption of something being broken is probably correct.  It won't be clear as to what is broken until the rear housing is removed for inspection. 

The process is rather simple.  Disconnect driveshaft, disconnect speedometer cable, remove slotted nut and output shaft yoke, remove secondary pump holding screw (along with spring and piston), remove transmission mount and cross member, and then remove the 8x1.25 bolts that hold the rear housing on.  The housing may need some persuasion, as the gasket and alignment pins may hold tight.  After the rear housing is removed you'll be able to see what is broken....the pawl or the gear.....maybe both.  Sometimes the pin that the pawl pivots on will want to come out when the rear housing is removed.  If so, then be aware of this happening so parts don't go flying into oblivion.....or in the transmission itself. 

The pawl simply slides off off a pivot pin, and there will be a spring keeping tension on it you'l have to take off along with the pawl.  If the gear has to be removed, then remove the speedometer drive gear and governor off of the output shaft, and then the gear.  Take note of the order in which everything goes, and be very careful with the metal rings that the governor slides over.  They're much like piston rings, and will break easily. 

Should you need a parking pawl or a parking gear, the gear (part number 722-272-00-17) will have to be sourced used, as it's no longer available, and the pawl itself (part number 115-278-02-21) can still be bought new from Mercedes for around $50-$60. 
1966 250se coupe`, black/dark green leather
1970 600 midnight blue/parchment leather
1971 300sel 6.3, papyrus white/dark red leather
1973 300sel 4.5, silver blue metallic/blue leather
1976 280s astral silver/blue MB Tex
1978 450sel 6.9 Euro, Anthr/velour

Jjutzy

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Re: Intro & Shifter linkage Gear selector Issue 79 300SD
« Reply #24 on: 05 December 2018, 07:56 AM »
Does anyone know if the collar nut on the yoke is the same size as the pre-chamber collar nut?

Will this tool do the trick?

https://mercedessource.com/store/615-616-617-early-601-and-603-diesel-prechamber-collar-nut-torquing-tool
1979 300 SD 348,000+ Miles

UTn_boy

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Re: Intro & Shifter linkage Gear selector Issue 79 300SD
« Reply #25 on: 05 December 2018, 04:48 PM »
Does anyone know if the collar nut on the yoke is the same size as the pre-chamber collar nut?

Will this tool do the trick?

https://mercedessource.com/store/615-616-617-early-601-and-603-diesel-prechamber-collar-nut-torquing-tool

No, and even if it was the same diameter the tabs are still of a different width, bevel, and depth.  Below is a picture of the nut and the socket that is used. 

1966 250se coupe`, black/dark green leather
1970 600 midnight blue/parchment leather
1971 300sel 6.3, papyrus white/dark red leather
1973 300sel 4.5, silver blue metallic/blue leather
1976 280s astral silver/blue MB Tex
1978 450sel 6.9 Euro, Anthr/velour