5.0l swap and trans discussion

[Quick4door]

I currently have a 1992 400 E which has roughly 300,000 miles on it. I have a 500 SL Parts car with the 119.972 engine and 722.5 trans. The transmission in the 400e is from sun valley transmissions and has about 20k on it since the complete rebuild. Should I just swap the SL engine and trans in? Does anyone know what the pros and cons are? I have the whole parts car here so I can use whatever wiring or sensors needed.

Pics of the 400e and the parts car.

 

[gsxr]

The R129 trans (722.3, not 722.5) has a different rear tail section and I am pretty sure it won't bolt up to the 400E. The R129 119.972 engine is 100% plug+play other than swapping the two wire harnesses.

You want to put the 5.0L engine in with the 20kmi-old rebuilt trans. I'd also fully reseal the 5.0 engine, and replace chain rails etc, with the engine on a stand prior to installing.

 

[Alphasud40]

I’m confused. I thought the 722.5 was only used on the M104 engine? So the SL500 has a M119 with a 5-speed 722.5?

 

[gsxr]

I’m confused. I thought the 722.5 was only used on the M104 engine? So the SL500 has a M119 with a 5-speed 722.5?

You are correct. The above is a typo. The 722.5 was never used behind any V8 engine.

1996-up with M119.98x (coil-on-plug, ME 1.0) had the 722.6 (NAG-1) five-speed.

 

[Alphasud40]

Yes, I think he is asking if he can swap the 96 and up drivetrain into his 400E. If so we have gone down that road before and let the fun begin. Unfortunately no easy swap for either engine or transmission. I have also seen parts SL cars for sale with the 500 badge but a M104 722.5 combo.

 

[gsxr]

Yes, I think he is asking if he can swap the 96 and up drivetrain into his 400E. If so we have gone down that road before and let the fun begin. Unfortunately no easy swap for either engine or transmission. I have also seen parts SL cars for sale with the 500 badge but a M104 722.5 combo.

He said the engine was 119.972 which would be up to 1995 with LH-SFI and 722.3... need some verification! You are right, the 96-up swap is a lot more complicated.

 

[Quick4door]

Thanks for the help guys. The car is a 1994SL 500 with The 119.972 and what I thought was a 722.5 transmission, I must be mistaken. Is there any reason to install the SL 500 transmission with the engine, is there any difference Between what I have and what this one has other than the mileage on the transmission?

I definitely plan on resealing the engine, I will take a look at the heads, and if they need to be pulled so that I can put new head, gaskets in, then I will do so. I am fairly confident at this point that the lower end does not need any attention, but I won’t know that until I get it on the engine stand and start taking things apart. My hope is that I can strip it down to a short block at worst, and replace or reseal everythingelse.

 

[Alphasud40]

Really no need to transfer the transmission from the SL if the 400E transmission is solid. I believe the 500 transmission has a larger torque capability but you should be okay. If the 500 transmission is good use it and keep the 400 as a spare. Everything else is a straight swap. All you need is the EZL and LH modules. Only other difference is if either one has ASR. Don’t forget to swap the differential for the 2.65 final drive. Then you will need to recalibrate the speedometer. Does either one have ASR?

 

[gsxr]

You want to put the 5.0L engine in with the 20kmi-old rebuilt trans. The SL500 transmission has identical internals, only the tailshaft housing & valvebody is different. They have the same torque rating.

The 1994 SL500 does have 2.65 rear axle ratio, unfortunately it is the "reinforced" diff which is physically larger and will not bolt in to the 400E. If you want 2.65's then source a diff from a 129.066 chassis (1990-1992 500SL, must match ASR or non-ASR based on what your 400E is).

 

[Quick4door]

Excellent info gents! The 400e trans will stay and I can sell the sl500 trans on marketplace. I already have the 2.65 rear diff from a 91 sl500. The sun valley trans has been flawless so no reason not to use it. I’m waiting for the weather to break for spring and I’ll yank the engine out of the sl to get started.

 

[ssaliaj]

Excellent info gents! The 400e trans will stay and I can sell the sl500 trans on marketplace. I already have the 2.65 rear diff from a 91 sl500. The sun valley trans has been flawless so no reason not to use it. I’m waiting for the weather to break for spring and I’ll yank the engine out of the sl to get started.

Dont forget to remove the kickdown relay , @gsxr saved my life with this suggestion. Car was shifting as hell after the 5.0 swap, once removed the relay everything is perfect.