Upgrading the 722.3 trans - PeachParts Mercedes-Benz Forum

Motor Head · #1 12-26-2007, 10:47 PM

I own a 1990 300SEL with the 722.351 trans. The transmission is ready for a rebuild but I would like to upgrade it to handle the additional power of the Mosselman twin turbo I will be installing. The power rating of 300 HP puts it in the ball park of a V8 load on the trans.

What I would like to do is convert it to a 722.350 configuration as fitted on the 560 SEL of the same year. The problem is I have been having trouble determining the differences in the internal hard parts, e.g. drums etc, that I need to accomplish the upgrade. I already have a 1st gear start valve body that also has a shift kit in it so I'm OK there.

The other question I have is that the trans whines (not loud but noticable) in second gear only. Other than that it shifts fine. Any ideas what would cause this condition?

Thanks,
Motor Head

Roncallo · #2 12-27-2007, 05:55 AM

Quote:

Originally Posted by Motor Head

I own a 1990 300SEL with the 722.351 trans. The transmission is ready for a rebuild but I would like to upgrade it to handle the additional power of the Mosselman twin turbo I will be installing. The power rating of 300 HP puts it in the ball park of a V8 load on the trans.

What I would like to do is convert it to a 722.350 configuration as fitted on the 560 SEL of the same year. The problem is I have been having trouble determining the differences in the internal hard parts, e.g. drums etc, that I need to accomplish the upgrade. I already have a 1st gear start valve body that also has a shift kit in it so I'm OK there.

The other question I have is that the trans whines (not loud but noticable) in second gear only. Other than that it shifts fine. Any ideas what would cause this condition?

Thanks,
Motor Head

I cant help you on the parts or your problem, but I can almost assure you that a good used 560SEL transmission would be far more cost effective than replacing hard parts in your current transmission, even if you rebuild the used transmission with new clutches and seals.

John Roncallo

Motor Head · #3 12-27-2007, 10:49 AM

That is an excellent idea which is my plan B if what I am trying to do proves to be too hard or too expensive. If I do go that route, I will likely get one thats been freshly rebuilt but at least I won't have to change the configuration.
Now that I have been looking at this for a while it has become a quest for knowledge on 722 technical data.

FLYNAVY · #4 12-27-2007, 01:25 PM

You will most likely have to swap out the output flange of the 722.35 for the smaller one that your original 722 had. The V8 cars have a 110 mm diameter flange that mounts to the driveshaft and flex discs, where the I6's have a 90mm flange. I'm looking into doing the same thing, and at least from the EPC diagrams that I have found, it appears the swap will work. Most of the part numbers are the same between the two trans, most importantly the bearings and seals that go around the flange.

pesho · #5 12-27-2007, 04:30 PM

Hi all, I'm new here been on the benzworld a little bit, got a 560SEC and since seeing PUMPISH M103 set-up am inspired to get rid of the m117 and drop in an M103 or 4 turbo.
On the tranny issue is the bellhousing between the I6 and V8 the same, and the felxplate/ring gear and torque converter and also kickdown cable?

Roncallo · #6 12-27-2007, 11:33 PM

Quote:

Originally Posted by pesho

Hi all, I'm new here been on the benzworld a little bit, got a 560SEC and since seeing PUMPISH M103 set-up am inspired to get rid of the m117 and drop in an M103 or 4 turbo.
On the tranny issue is the bellhousing between the I6 and V8 the same, and the felxplate/ring gear and torque converter and also kickdown cable?

Dont get me wrong. PUMPISH has a great car and great work. But may I just ask the question?

Why not do what PUMPISH did to a V8 preferably an M119 V8.

John Roncallo

FLYNAVY · #7 12-28-2007, 01:30 AM

I agree....for gods sake don't back track! The I6 is a strong reliable motor, but its gonna be HUGE money to get it anywhere close to where you start out with the 560....assuming you don't want the motor to go "bang" after a few thousand miles anyway

RBYCC · #8 12-28-2007, 09:40 AM

Quote:

Originally Posted by FLYNAVY

I agree....for gods sake don't back track! The I6 is a strong reliable motor, but its gonna be HUGE money to get it anywhere close to where you start out with the 560....assuming you don't want the motor to go "bang" after a few thousand miles anyway

Don't sell the M103/M104 short as far as being able to make power.

The stock transmission he has will more then handle a Mosselman TT install.

I'm running a stock 722.358 with 63K miles behind a M103-12V Turbotechnics twin turbo.

Making about 350+ HP and Torque.

Performance is faster then any 4.3L, 5,4L NA AMG V8.
Runs low five seconds to sixty mile per hour.

You don't have to build a 1000HP "hand grenade" that will ultimately explode....

Roncallo · #9 12-28-2007, 10:16 AM

Quote:

Originally Posted by RBYCC

Don't sell the M103/M104 short as far as being able to make power.

The stock transmission he has will more then handle a Mosselman TT install.

I'm running a stock 722.358 with 63K miles behind a M103-12V Turbotechnics twin turbo.

Making about 350+ HP and Torque.

Performance is faster then any 4.3L, 5,4L NA AMG V8.
Runs low five seconds to sixty mile per hour.

You don't have to build a 1000HP "hand grenade" that will ultimately explode....

No the 103 is not short on HP but a stock M119 starts life at 315 HP and more than likely more torque over a wider range than your 350HP M103.

My biggest question is this choice is it's application into a 560SEC. The 560SEC is a luxury coupe. When you start to pull 350 HP from a 103 is has to be a whinny screaming engine. In my opinion this type of application into a 560SEC will reduce the value of the car. 450HP can be had out of an M119 without much effort or suffering of drive ability. Or 700 to 1000 HP can be done with a whinny screaming scenario. I believe an M119 installed into a 560SEC will increase the value of the car even with performance enhancements up to about 500 HP as long as the spirit of the car remains intact.

My personal #1 choice for the 560SEC is the M120 V12. See Steve in SoCal sticky on this. If you loose the throttle by wire and MB engine management this becomes an affordable option. But I would put a Chevy 7.0 liter vett engine in as a second choice.

John Roncallo

jhodg5ck · #10 12-27-2007, 09:25 PM

I6 and V8 bell housings, torque converters are Very different.

As an aside, we can rebuild your box with kevlar bands and high performance clutches, valve body springs etc..

Jonathan

Roncallo · #11 12-28-2007, 09:24 AM

Quote:

Originally Posted by jhodg5ck

I6 and V8 bell housings, torque converters are Very different.

As an aside, we can rebuild your box with kevlar bands and high performance clutches, valve body springs etc..

Jonathan

May I ask who is we. I would love to find a source of high performance MB transmission parts. Also a good selection of rear end ratios would also be nice.

John Roncallo

jhodg5ck · #12 12-28-2007, 09:29 AM

We = Me.
http://blueridgemb.com/?p=85

Rear's...that's a bit of a dig..especially one that's going to take the torque of an M120!

Jonathan

pesho · #13 12-28-2007, 02:45 PM

SORRY that was me that sidetracked a little with the 560sec..
on the topic it, the 722.358 is what came with the 300CE? What is the difference between the 722.351 that Motor Head has in the 300sel? And back to the original question as Jonathan mentioned it wouldn't make any sense to go with the 560 722.350 as it will not bolt to the M103. Sounds like the easiest thing is to rebuilt your 300sel tranny and beef it up, probably the most cost effective.
Off topic:
TT'ing a V8 either a M117 or M119 would be great and it has been done, but was leaning to the M103-04 as its much simpler. Less parts...2 less heads to worry about, 2 less cylinders and the biggest reason is the clearance. A TT M119 in a w126 would be a nightmare to get the manifolds and down pipe to fit and the driverside on my 560sec has the ABS/ASR unit that looks like would be in the way. With the M103-04 you can call the engine bay a living room..
Again sorry for getting this thread off topic.

Motor Head · #14 12-29-2007, 10:42 AM

Wow guys. I had no idea I was going to create this kind of discussion when I openned the thread. Great discussion and it seems that many of us are passionate about solving problems and finding out about tranny upgrades especially for use with power adders.
My rationale, however flawed, is to make the most out of what I've got which is the 103 engine. I never wanted to make a race car out of it but 300 HP sounds a lot more appropriate for a W126 chassis than 188 HP. Also, out here in California, the gas prices are going through the roof and I don't want the permanent penalty of 15 miles to the gallon by running the 560 engine.
I have also swapped my rearend out for a 350 SDL unit which has a 2.88 ratio (available at a junkyard near you!) and the car is so much more pleasant to drive now that it is not turning 3400 rpm at 70 mph. I also saw an additional couple of mpg but that is combined driving. I'm about to leave for a long raod trip today so I will get to see what it does freeway only.
But back to the turbo.

To me it has to be a systems solution.

Define the problem: heavy car, underpowered

Solution: want to retain good mileage, reliably increase power but only when I need it, and increase engine life

Approach:
1. Change rear gear from 3.46 to 2.88. Reduced engine wear and increased mileage (friction increases with the square of the rpm)
2. Update transmission either with high performance parts as seen previously in this thread or try to convert to 560 spec (current problem)
3. Install Mosselman kit: V8 power only when I need it, I6 mileage when I don't, now I can pull the rearend gear better (and uphill) and it may open the door for a gear vendor which actually has an application for the 722 trans.

As has also been mentioned in this post, if I can upgrade my I6 case with the right internals, I won't have to deal with the bell housing issue that was also identified.

Interestingly I found a shop on the internet called Freddies Transmission http://www.freddiestransmissions.com/ who say they can do what I am asking. As soon as I find out the particulars from them about what is involved I will post them here.

Thanks for all the great discussion. I have learned a lot.

FLYNAVY · #15 12-29-2007, 12:19 PM

I understand where you are coming from, but don't expect to get better gas mileage w/ the turbo set-up. Just from a physics/thermodynamic standpoint, the fuel needed to generate 300 HP is essentially the same in either motor (though the torque curve is different over the power band, it will average out in a similar way). If you look at the amount of air and fuel needed to get x amount of HP, it will be similar whether its in a motor cylinder, or in a pot of coffee. Of course its not really that simple, as you get into flow efficiency, fuel atomization (and how much of the fuel you squirt in actually ends up burning), and a few other things.....but you can approximate things pretty well at least. If you are not "on it" all the time, your gas consumption would be better, but it really isnt that bad driving that way w/ a V8 either. I think the best thing you could do if you are concerned about gas mileage is do the rear end swap you were talking about, though it will hurt acceleration somewhat