240d manual shifting - PeachParts Mercedes-Benz Forum

BATComm1966 · #1 03-08-2019, 01:09 PM

When I got the car the PO said it had a lite "grind" going into second... If I go slow and don't wrap up the RPM I can get it into 2nd gear and "spirited" shifting is out the door... My question is.. Anyone on here of average mechanical ever rebuilt one of these 4spds I'm guessing it's a synchro that's shot because everything else is fine....

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mabbonizio · #2 03-08-2019, 08:02 PM

try changing the transmission oil first. Half pennzoil synchromesh and half ATF cured my grind into 3rd gear.

party · #3 03-08-2019, 08:58 PM

I've read numerous accounts of Redline MTL smoothing shifting in boxes with worn synchros.

BATComm1966 · #4 03-09-2019, 03:56 PM

I've got the Redline MTL on the shelf.. Going to try that first..

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BATComm1966 · #5 03-09-2019, 03:58 PM

Correction I have Redline MT-90

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Sugar Bear · #6 03-09-2019, 04:31 PM

Agree it is likely a synchro, try the oils as suggested and replace the shifter bushings and adjust the shifter linkages, it makes a big difference.

About rebuilding the trans, an average mechanic with a manual can do it; but, a good used unit may be less expensive and faster.

IIRC, there is an aluminum and iron version of those transmissions. I don't know if they are interchangeable...anybody???

BATComm1966 · #7 03-09-2019, 05:08 PM

Going to give this MT-90 a shot first since i have it!!

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Frank Reiner · #8 03-09-2019, 06:32 PM

Quote:

Originally Posted by BATComm1966

When I got the car the PO said it had a lite "grind" going into second... If I go slow and don't wrap up the RPM I can get it into 2nd gear and "spirited" shifting is out the door... My question is.. Anyone on here of average mechanical ever rebuilt one of these 4spds I'm guessing it's a synchro that's shot because everything else is fine....

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BATman:

The subject of synchros and various lubricants comes up from time-to-time.
1) Iron cases were used thru approx. 1981-82, aluminum cases thereafter. What year is yours?
2) Both iron and aluminum case boxes use ATF as the lube. A common reason for poor synchro operation is the use of "gear" oils, including MTL and MT-90. Those oils do a great job in boxes that originally used oils that have viscosity above 75. They also contain ingredients that make them very slippery (aka, friction modifiers). The friction modifiers are exactly what lead to poor synchro operation, and gear "grind".
3) The synchro on 2nd gear receives more wear than the other three, and will exhibit "grinding" first.
4) Type F ATF does not contain friction modifiers, and hence will give a synchro the best chance to grab on the gear cone and produce a quiet engagement. It is a low cost test.

Rebuilding of the aluminum version is the easier job vs. the iron version.

BATComm1966 · #9 03-09-2019, 06:42 PM

Quote:

Originally Posted by Frank Reiner

BATman:

The subject of synchros and various lubricants comes up from time-to-time.
1) Iron cases were used thru approx. 1981-82, aluminum cases thereafter. What year is yours?
2) Both iron and aluminum case boxes use ATF as the lube. A common reason for poor synchro operation is the use of "gear" oils, including MTL and MT-90. Those oils do a great job in boxes that originally used oils that have viscosity above 75. They also contain ingredients that make them very slippery (aka, friction modifiers). The friction modifiers are exactly what lead to poor synchro operation, and gear "grind".
3) The synchro on 2nd gear receives more wear than the other three, and will exhibit "grinding" first.
4) Type F ATF does not contain friction modifiers, and hence will give a synchro the best chance to grab on the gear cone and produce a quiet engagement. It is a low cost test.

Rebuilding of the aluminum version is the easier job vs. the iron version.

More reading leading me to this also, and correct a cheap test

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BATComm1966 · #10 03-09-2019, 07:32 PM

Quote:

Originally Posted by BATComm1966

More reading leading me to this also, and correct a cheap test

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Sorry mine is an 81

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party · #11 03-09-2019, 07:33 PM

Redline MTL is spec'd for gearboxes that call for ATF from the factory. I can tell you all that it works great in my 5spd with no grinds as well as a few MB 5spd cars I've been in.

From the Redline site:

Quote:

Since most GL-5 gear oils for differentials are too slippery for manual transmissions, Red Line offers these products that ensure proper shifting while providing ultimate wear protection

Appropriate coefficient of friction for most manual transmission synchronizers (other's synthetic gear oils are often too slippery for proper synchro engagement)

https://www.redlineoil.com/mtl-75w80-gl-4-gear-oil

Frank Reiner · #12 03-09-2019, 07:51 PM

And this also from Redline:

D4 ATF

Our most versatile ATF, use where Dexron III®, Dexron II®, Mercon® and Mercon V® fluids are recommended, for use in automatic, manual transmissions and power steering
Popular applications: Toyota Type T-III and T-IV, Honda ATF-Z1, Nissan Matic D, J & K, Diamond SP-II, SP-III, Mazda ATF M-V, most BMW and Audi/VW automatic transmissions
Also used with manual transmissions and transaxles like T-5, T-45, T-56 and late-model BMW, provides a GL-4 level of gear protection
Excellent cold weather operation

party · #13 03-09-2019, 08:37 PM

The D4 kinda jogged my memory. From what I remember reading online, most were saying that if MTL shifts a little rough when it's cold the next step down in viscosity is D4. Being in CA everyone out here is using MTL and it's working well for them all year long.