1-2-3-4-(crunch)5-6
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1-2-3-4-(crunch)5-6
Over the past few weeks, I've noticed a weird occurrence while shifting from 4th to 5th during aggressive driving. All other shifts are as smooth as the MB gearbox will allow, but the 4-5 upshift has been almost a "grind" as if you let the clutch out too early before plugging into the gear. The gear grabs just fine, and I don't miss the shift, but you hear it grind for a millisecond and can clearly feel it in the shifter. This is never felt during normal driving, or even 50% throttle. Only on the "speed runs" where the load is high.
If I wait a split-second between the 4-5 shift and gently coax the shifter into 5th, no crunch. 5-6 upshift, even when shifted aggressively, is smooth. It's just when you're shifting aggressively that the "crunch" (for lack of a better term) is felt in the 4-5 upshift. Downshifting from 6th to 5th is smooth as silk.
What is this a symptom of? The clutch feels nice and firm, and no other shifts are affected. No clutch slip detected.
I will be doing a fluid flush and refill with the OEM Mercedes fluid required. The transmission has 57,000 miles on it.
Thoughts?
If I wait a split-second between the 4-5 shift and gently coax the shifter into 5th, no crunch. 5-6 upshift, even when shifted aggressively, is smooth. It's just when you're shifting aggressively that the "crunch" (for lack of a better term) is felt in the 4-5 upshift. Downshifting from 6th to 5th is smooth as silk.
What is this a symptom of? The clutch feels nice and firm, and no other shifts are affected. No clutch slip detected.
I will be doing a fluid flush and refill with the OEM Mercedes fluid required. The transmission has 57,000 miles on it.
Thoughts?
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From: Murfreesboro, TN
Re: 1-2-3-4-(crunch)5-6
Originally Posted by oledoc2u
John I have never looked at or know much about the manuel tranny in the limited's. I know when this happens in a big truck, it can be two things, synchrinizers in the tranny, or linkage out of adjustment, just a bit. May not apply here though...
That, combined with the fact that I have zero problems in any other gears.
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Re: 1-2-3-4-(crunch)5-6
Originally Posted by oledoc2u
John I have never looked at or know much about the manuel tranny in the limited's. I know when this happens in a big truck, it can be two things, synchrinizers in the tranny, or linkage out of adjustment, just a bit. May not apply here though...
Otherwise, like my prized Alpha Romeo Spyder, sadly, it was the tranny synchros.
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Re: 1-2-3-4-(crunch)5-6
If it's the synchros I'll end up swapping in a manual gearbox from another Limited... the bill for some tech to poke around for three days and replace parts will be thousands.
I'm going to try the flush/fill sometime before I send my car to San Antonio... People on MB-World had rave reviews about Redline MTL fluid transforming the clunky MB gearbox into a smooth-shifting machine. Royal Purple makes a fluid called Synchromax which has also gotten decent reviews, but Redline MTL is a fluid we use with Nissan Motorsports and it does a splendid job.
It's $14 a quart... much cheaper but allegedly better than the factory fluids, being as it's a synthetic.
I'm going to try the flush/fill sometime before I send my car to San Antonio... People on MB-World had rave reviews about Redline MTL fluid transforming the clunky MB gearbox into a smooth-shifting machine. Royal Purple makes a fluid called Synchromax which has also gotten decent reviews, but Redline MTL is a fluid we use with Nissan Motorsports and it does a splendid job.
It's $14 a quart... much cheaper but allegedly better than the factory fluids, being as it's a synthetic.
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Re: 1-2-3-4-(crunch)5-6
Originally Posted by JHM2K
I'm leaning towards the linkage adjustment. Wouldn't a bad syncro in 5th cause problems in both up and down-shifting?
That, combined with the fact that I have zero problems in any other gears.
That, combined with the fact that I have zero problems in any other gears.
As you say, you've got to pay to play.
Each gear has it's own synchro, and a new synchro and gear is an option. This is of the top of my head and I will check it out for accuracy.
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Re: 1-2-3-4-(crunch)5-6
Direct from the service manual:
DIAGNOSIS AND TESTING
LOW LUBRICANT LEVEL
A low transmission lubricant level is generally the result of a leak, inadequate lubricant fill, or an incorrect lubricant
level check.
Leaks can occur at the mating surfaces of the gear case and adaptor or from the front/rear seals. A suspected leak
could also be the result of an overfill condition.
Leaks at the rear of the extension or adapter housing will be from the housing oil seals. Leaks at component mating
surfaces will probably be the result of inadequate sealer, gaps in the sealer, incorrect bolt tightening, or use of a
non–recommended sealer.
A leak at the front of the transmission will be from either the front bearing retainer or retainer seal. Lubricant may
be seen dripping from the clutch housing after extended operation. If the leak is severe, it may also contaminate the
clutch disc causing the disc to slip, grab, and/or chatter.
A correct lubricant level check can only be made when the vehicle is level. Also allow the lubricant to settle for a
minute or so before checking. These recommendations will ensure an accurate check and avoid an underfill or overfill
condition. Always check the lubricant level after any addition of fluid to avoid an incorrect lubricant level condition.
level check.
Leaks can occur at the mating surfaces of the gear case and adaptor or from the front/rear seals. A suspected leak
could also be the result of an overfill condition.
Leaks at the rear of the extension or adapter housing will be from the housing oil seals. Leaks at component mating
surfaces will probably be the result of inadequate sealer, gaps in the sealer, incorrect bolt tightening, or use of a
non–recommended sealer.
A leak at the front of the transmission will be from either the front bearing retainer or retainer seal. Lubricant may
be seen dripping from the clutch housing after extended operation. If the leak is severe, it may also contaminate the
clutch disc causing the disc to slip, grab, and/or chatter.
A correct lubricant level check can only be made when the vehicle is level. Also allow the lubricant to settle for a
minute or so before checking. These recommendations will ensure an accurate check and avoid an underfill or overfill
condition. Always check the lubricant level after any addition of fluid to avoid an incorrect lubricant level condition.
HARD SHIFTING
Hard shifting is usually caused by a low lubricant level, improper, or contaminated lubricants. The consequence of
using non–recommended lubricants is noise, excessive wear, internal bind, and hard shifting. Substantial lubricant
leaks can result in gear, shift rail, synchronizer, and bearing damage. If a leak goes undetected for an extended
period, the first indications of component damage are usually hard shifting and noise.
Shift component damage, incorrect clutch adjustment, or a damaged clutch pressure plate or disc are additional
probable causes of increased shift effort. Incorrect adjustment or a worn/damaged pressure plate or disc can cause
incorrect release. If the clutch problem is advanced, gear clash during shifts can result. Worn or damaged synchro
rings can cause gear clash when shifting into any forward gear. In some new or rebuilt transmissions, new synchronizer
rings may tend to stick slightly causing hard or noisy shifts. In most cases, this condition will decline as
the rings wear-in.
using non–recommended lubricants is noise, excessive wear, internal bind, and hard shifting. Substantial lubricant
leaks can result in gear, shift rail, synchronizer, and bearing damage. If a leak goes undetected for an extended
period, the first indications of component damage are usually hard shifting and noise.
Shift component damage, incorrect clutch adjustment, or a damaged clutch pressure plate or disc are additional
probable causes of increased shift effort. Incorrect adjustment or a worn/damaged pressure plate or disc can cause
incorrect release. If the clutch problem is advanced, gear clash during shifts can result. Worn or damaged synchro
rings can cause gear clash when shifting into any forward gear. In some new or rebuilt transmissions, new synchronizer
rings may tend to stick slightly causing hard or noisy shifts. In most cases, this condition will decline as
the rings wear-in.
TRANSMISSION NOISE
Most manual transmissions make some noise during normal operation. Rotating gears generate a mild whine that is
audible, but generally only at extreme speeds.
Severe, highly audible transmission noise is generally the initial indicator of a lubricant problem. Insufficient,
improper, or contaminated lubricant will promote rapid wear of gears, synchronizers, shift rails, forks and bearings.
The overheating caused by a lubricant problem can also lead to gear and bearing damage.
audible, but generally only at extreme speeds.
Severe, highly audible transmission noise is generally the initial indicator of a lubricant problem. Insufficient,
improper, or contaminated lubricant will promote rapid wear of gears, synchronizers, shift rails, forks and bearings.
The overheating caused by a lubricant problem can also lead to gear and bearing damage.
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Re: 1-2-3-4-(crunch)5-6
Originally Posted by JHM2K
So, one synchro... and we know which gear... any stabs as to what that repair bill would run?
Might be worth a call to Speedriven...
Might be worth a call to Speedriven...
Last edited by LantanaTX; 11-03-2011 at 04:55 PM.
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Re: 1-2-3-4-(crunch)5-6
Originally Posted by JHM2K
So, one synchro... and we know which gear... any stabs as to what that repair bill would run?
Might be worth a call to Speedriven...
Might be worth a call to Speedriven...
I cannot quite understand it, but things are much clearer when you have all the parts out and laying in a heap on the garage bench, so get to it.
Oh, do not lose anything or have anything left over when you finish.There is no adjustment by the way, made too accurate for that requirement.
I did a 1954 Austin gearbox once and it ran just fine when I finished, four reverse gears and one forward.
Last edited by onehundred80; 11-03-2011 at 05:22 PM.