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  #1  
Old 10-22-2012, 07:40 AM
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722.5xx in 126

Has anyone put a 722.5 5 speed in a 420, 500, 560 126 car? I would love to have one in my 84 500SEL. I can handle the electrical part, just need to know if it will fit. Will I have to have a drive shaft made for it?

Thanks
Paul

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  #2  
Old 02-06-2013, 08:45 PM
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I'm investigating going the other way in a 300SL, From looking at breakdowns, the 722.5 is a 5 speed and the 722.3 a 4, overall length appears to be the same.

It looks like the 5 speed could not hold a big motor in 5th so they just eliminated 5th and called it a 722.3.
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  #3  
Old 02-07-2013, 07:27 AM
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From some research I think the 722.3 has been made starting sometime in the late 70's or 80's. They were used in the S class for all engines. The 722.4 came later and was used in the smaller cars. So I gather from what you are saying that the 722.5 is a 722.4 with a 5th gear. I made the mistake of putting a 403 ci engine in a mid 80's Buick Riveria FWD which only came with a 300 ci or smaller. Yes that 403 would brake the front axles if you were not careful. Is there a 722.XXX overdrive for the bigger engines that you know of?

Thanks Paul
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  #4  
Old 02-07-2013, 07:36 PM
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The 722.6 is probably the only official 5 sp to hold a big motor.

But, think about this, if your car isn't likely to see an additional 100,000 miles in the near future and you consider the trans to be a wear item, a 722.5 would probably work. Some sort of shift kit / higher line pressure would probably keep it going.

The 722.6 needs a electronic controler, take a look at the performance section on this site, someone is developing a stand alone control for just under $ 1,000.

The 722.3 and 722.5 are basically the same trans, the 722.5 has overdrive in the tail of the case. The two trans even take the same pan gasket.

The 722.4 is the small trans

I'm only investigating this because I have a ragged 91 300SL that is turning into a track day car. The end plan is to use a 97 M104 / 722.6 but I'm real tempted to fix / replace the currently bad 722.5 and run it until the 300 - 24V motor expires. Using a 722.3 would give me a wider range of parts.

From this thread
722.4 and 722.3, interchangeable?

Torque capacity
The designation W4A0xx tells us the maximum input torque in kpm (kilopondmeter).
1kpm=7.23lb/ft.

722.0 (W3A040)- 290lb/ft
722.1 (W4B020 or W4B025)- 145/180lb/ft
722.2 (W4B025)- 180lb/ft
722.3 (W4A040)- 290lb/ft
722.4 (W4A020)- 145lb/ft
722.5 (W5A030)- 216lb/ft
722.6 (W5A580)- 578lb/ft

G-models
720.1?x (W4A018)- 130lb/ft
722.39x (W4A028)- 202lb/ft
722.61x/63x (W5A330)- 216lb/ft (Used W5A580 in the larger engine models)

Note: The 300D/TD/CD/SD from October 1984-on (with the 2.88 rear end) used the weaker 722.4 transmission.

that from superturbodiesel.com.
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  #5  
Old 02-07-2013, 07:54 PM
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Quote:
Originally Posted by 97 SL320 View Post
The 722.6 is probably the only official 5 sp to hold a big motor.

But, think about this, if your car isn't likely to see an additional 100,000 miles in the near future and you consider the trans to be a wear item, a 722.5 would probably work. Some sort of shift kit / higher line pressure would probably keep it going.

The 722.6 needs a electronic controler, take a look at the performance section on this site, someone is developing a stand alone control for just under $ 1,000.

The 722.3 and 722.5 are basically the same trans, the 722.5 has overdrive in the tail of the case. The two trans even take the same pan gasket.

The 722.4 is the small trans

I'm only investigating this because I have a ragged 91 300SL that is turning into a track day car. The end plan is to use a 97 M104 / 722.6 but I'm real tempted to fix / replace the currently bad 722.5 and run it until the 300 - 24V motor expires. Using a 722.3 would give me a wider range of parts.

From this thread
722.4 and 722.3, interchangeable?

Torque capacity
The designation W4A0xx tells us the maximum input torque in kpm (kilopondmeter).
1kpm=7.23lb/ft.

722.0 (W3A040)- 290lb/ft
722.1 (W4B020 or W4B025)- 145/180lb/ft
722.2 (W4B025)- 180lb/ft
722.3 (W4A040)- 290lb/ft
722.4 (W4A020)- 145lb/ft
722.5 (W5A030)- 216lb/ft
722.6 (W5A580)- 578lb/ft

G-models
720.1?x (W4A018)- 130lb/ft
722.39x (W4A028)- 202lb/ft
722.61x/63x (W5A330)- 216lb/ft (Used W5A580 in the larger engine models)

Note: The 300D/TD/CD/SD from October 1984-on (with the 2.88 rear end) used the weaker 722.4 transmission.

that from superturbodiesel.com.
A member in Sweden has made one for under $600....
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  #6  
Old 02-08-2013, 08:22 AM
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Thanks for the information everyone. I don't think I want to go as far as a 722.6 but I am going to keep a eye out for a 722.5. I'm not sure what the torque is in my car as the engine is a low compression engine from Mexico. It has plenty of power for me and it runs best on low octane regular fuel. I have a 560 ready to go in but the 500 is cheaper to operate (20+mpg on the highway with regular fuel). So I think the 733.5 would probably be fine. I'll let you know IF I find one and how it works.

Paul
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  #7  
Old 02-08-2013, 10:11 PM
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Note: The 300D/TD/CD/SD from October 1984-on (with the 2.88 rear end) used the weaker 722.4 transmission.

My 85 300sd came with a 722.3 from MB
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  #8  
Old 02-09-2013, 09:24 AM
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What rear end ratio does your 300SD have?
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  #9  
Old 02-09-2013, 11:36 AM
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Why bother with the 722.5. It's the same amount of work for A .6. I can buy them from my local junkyard for $125.
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  #10  
Old 02-09-2013, 05:10 PM
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The .6 needs electronic control and is much different than the .3 / .5. The .3 / .5 has a neutral / backup switch by the shift lever where the .6 does not. The .3 and .5 are much closer to each other than the .6 is to either.

Looking at better pics of the .3 and .5, the .5 might be slightly longer bell housing to drive shaft flange but the mount location looks the same. In any event, the added length should not be an issue as the driveshaft can easily be shortened..
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  #11  
Old 02-10-2013, 07:08 PM
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I just thought of something. . . The 722.3 / .5 have a one piece case ( built in bell housing ) so there won't be a 722.5 with a V8 bell unless there was a very rare build I haven't come across.

The M103 / M104 straight 6 and M110 4 cyl pattern was made in the 722.3 and 722.5 so swapping there is possible.

But, there is still hope for the 5 speed V8, use the .3 case and add the .5 OD unit / tailshaft / valve body. This all assumes that the main case is similar enough between the .3 and .5.
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  #12  
Old 02-10-2013, 09:53 PM
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Quote:
Originally Posted by 97 SL320 View Post
What rear end ratio does your 300SD have?
I don't know but the tech data book says 84 & 85 are 2.88, up to 83 is 3.07.
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  #13  
Old 02-11-2013, 10:31 AM
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Are you just looking for lower revs? The 2.47 is already pretty low rev at highway speeds...in 4th gear. You may end up using more fuel by lowering the rpms too far in final drive by lugging the motor. A normal 560 would probably handle it fine, but a lower output 500 not so sure about that....you'd be likely looking at 2000rpm or less at 75mph with a 5th gear.
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  #14  
Old 02-11-2013, 01:09 PM
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pawoSD. You have a good point. My 500 has good torque at 2000 but better at 3000. Now 75 mph is 2500 so I will probably leave it that way. This car will get 20 mpg on the highway so I guess I should just leave it alone. The best mileage I ever got was 23 and that was on a tank of fuel going from NC to Fla. I was running along with a group of truckers. Not drafting or anything, but I know they knew where the smokeys were and was running at 90 to 100 for quite a few miles. I know that a lot of the people here will say that is impossible to get batter mileage at that kind of speed, but think about this. In Germany these cars were designed to run 140+ mph all day long. At that rate, they wouldn't get but 25 or 30 miles per tank if you believe that higher the speed, lower the mpg. I say that a car can be designed to run very high speed and get good mileage doing it. but low speed mpg suffers. Using state highways, I am lucky to get 15 mpg. 10 mpg in stop and go traffic. If I run into a good buy on a 722.5 I may try it anyway.

Paul

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