300d non turbo swap to 300d turbo - Mercedes-Benz Forum
 
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post #1 of 6 (permalink) Old 06-01-2013, 05:24 AM Thread Starter
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Question 300d non turbo swap to 300d turbo

My car has already been swapped into to a turbo motor but it started out an 81 non turbo. My only questions is, I've been reading in here and it says the non turbo tranny won't bolt up to the turbo motor. Both my tech and the guy I'm buying from, say it will and the non turbo tranny is more reliable. Is any of this true? I find it hard to believe that MB would make an entirely new tranny for just the turbo motor and do it for no reason, when the tranny they already had in several cars was fine for the job. Anyone shed any light on this for me?
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post #2 of 6 (permalink) Old 06-01-2013, 05:52 AM
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That's not true.

The OM617 turbo or non turbo engine will bolt up to many transmissions. The problem is that you'll end up with shift points that might not suit your set up and throttle linkages that are different from your original configuration.

The 722.118 was fitted to non turbo OM617s. It came in two guises - no vacuum modulation but with a solid rod connection to the throttle linkage; and vacuum only with a dashpot for modification of the modulation pressure but no throttle linkage.

The OM617 turbo was first fitted with a 722.120 in the W116 300SD. This had both vacuum dashpot and a solid rod throttle connection.

The OM617 turbo was also fitted with a 722.303 in the W126 300SD which has a Bowden cable throttle linkage and a vacuum dashpot. This has an electronic speedometer connection.

The OM617 turbo when fitted to the W123 had a 722.315 transmission with a Bowden cable and a dashpot. This time a mechanical speedometer drive was used. (the 722.303 was also fitted to the last years of the 300TDT)

There were also some 722.405 transmissions with Bowden cable and dashpot mechanical speedometer fitted to the last years of the non turbo OM617s.

The 722.416 was fitted to the last years of the OM617 turbos - again with Bowden and dashpot.

These are transmissions that were officially fitted to the OM617 (turbo or not) other transmissions may physically fit.

Each transmission is mated to a particular final drive ratio so that the shift points happen at the correct road speeds for the type of engine that was to be used.

Generally speaking 722.1 transmissions are considered to be less reliable than 722.3 transmissions. 722.4 transmissions are considered to be worse than the 722.3s

The 722.1 transmission is beautifully made.

The 722.3 transmission is full of pressed steel junk (compared with the beautiful castings in the 722.1)

722.1s tend to have front end problems - primary pump + knackered splined shafts

722.3s tend to have buggered back ends - dodgy governors

All of these transmissions have seen interstellar mileages on them so I think it is difficult to say oh this one is bad and this one is better.
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post #3 of 6 (permalink) Old 06-01-2013, 07:09 AM Thread Starter
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So, I guess what I am asking is, will the work just fine for driving around in the city, with rare to never seeing highway use? Or should I try and locate a rear end from an 85 w123? I've heard this model has the highest ratio... my car will be a 98% city car and might see 100 miles a month.
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post #4 of 6 (permalink) Old 06-01-2013, 09:33 AM
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skip the 2.88 diff, you will be fine sticking with 3.07. no idea about the shift points though.
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post #5 of 6 (permalink) Old 06-01-2013, 10:46 AM
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If you have the original differential still fitted to the car you'll have a 3.46 =>

Differential identification? - PeachParts Mercedes ShopForum

Ideally you should have the 3.07 as brickton says - your shift points will be happening too early; for lots of town driving this might be a pain in the arse and on the odd occasion that you go on the highway the top end speed will be too low. Changing the differential will raise your shift points and maximum speed by 11%.

Even so I'd give it a go. When it gets into 2nd gear you should be quite nippy about town - though 3rd might come in a bit early. It all depends on your driving style and the speeds at which you want to travel.
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post #6 of 6 (permalink) Old 06-01-2013, 12:01 PM Thread Starter
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Quote:
Originally Posted by Stretch View Post
If you have the original differential still fitted to the car you'll have a 3.46 =>

Differential identification? - PeachParts Mercedes ShopForum

Ideally you should have the 3.07 as brickton says - your shift points will be happening too early; for lots of town driving this might be a pain in the arse and on the odd occasion that you go on the highway the top end speed will be too low. Changing the differential will raise your shift points and maximum speed by 11%.

Even so I'd give it a go. When it gets into 2nd gear you should be quite nippy about town - though 3rd might come in a bit early. It all depends on your driving style and the speeds at which you want to travel.
My average highway speed in my Lexus is between 70mph and 75mph. This car will see a monthly trip 25 miles north to my parents house but only 10 miles of that will be highway. I've heard that the 3.46 differential makes these turbos a lot of fun for city driving and that's all ill be doing. Don't really have much of a heavy foot but it will be welcome when needed. Thank you guys. I'll keep you posted on my car progress in the coming weeks!
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