SEC - Gearbox Conversion

[Francois]

Hi,

Would it be worth it to try and replace the gearbox in a '83 380 SEC with a newer fivespeed box?

Since I have only been driving manual cars, I don't know how easy it is to change a gearbox on a auto.

If this is not a good idea, then what can I do to make this box more efficient?

 

[talbir]

Francois,

Yes, you can bolt up the 722.370 transmission, from a 1992 -1996 W140. It has the hydraulic pressure switch on the side of it. Certain EZL units have the input for this switch. It's a strong unit with a shorter 1st gear ratio.

With the swap of the tailshaft and yolk it will bolt-up onto the W126 with no issues.

Result will be a much stronger bulletproof tranny, with better downshifts and upshifts. A far more respnsive unit.

Talbir

 

[Francois]

Great! Now just to find one of these boxes, and someone that would be able to do the conversion.

Thanks for the info!

 

[Francois]

Hi,

This might sound stupid, but what is an EZL? If my car does not have this, would the W140 box still work?

Regards

 

[talbir]

Yes, gearbox will still work - the EZL on your car may not have the input for the gearbox since it is an early 380.

I would go to the breaker and find a low mileage W140 V8 car(420 or 500)...but before this, check with your tech that he's happy to do the job.

 

[Francois]

Thanks Talbir! I am sure he will not have a problem doing this.

 

[Andy]

Hi

Just remember the g\box Talibar is advocating is NOT 5speed!!!



As for bullet proof. Yes they are strong. But I have found if reverse starts to be a problem ie Takes a long time for it to engage & this is not sorted sooner rather than later. The circlip for reverse piston gets pushed off its seats & all the return springs for reverse piston get destroyed & travel around the box. This can happen on any of the hydraulic boxes. But in my experience tends to happen on 140 boxes more so.

Having said that. It would not put me off a 140. But would I bother fitting one to a SEC. Is another matter.

You pays your money & make you own choice.

Personally. If I were you I would save & purchase the last of the SEC'S. These vehicles are vastly supperior to the earlier models & a LOT more releiable.


Regards

Andy @ www.mercedesservicing.com

 

[talbir]

As Andy has said, 722.370 trannies are 4-speed - forgot to validate that in my original post. 5-spd's were only introduced late 96.

The hydraulic problems mentioned are worth noting - but the advantages of the 140 tranny's over any of the late 126 ones are vast. Far more responsive shifting, shorter 1st gear ratio....not to mention the performance of your car will be greatly improved acros the gears......bolt up a late 126 tranny and you will not notice any difference whatsoever. And you could end up with exactly the same problems as on the 140 box.

5-spd is unneccesary - 4spd box with better performance is worth spending your money on. Cost of box and labour won't differ much between 140 and 126 trany - so why not put the money into the better box ???

 

[talbir]

Francois,

BTW, your 380 used a 4 plate, dual band pack transmission. It's no heavier duty than a 6-cylinder 300SE transmission.

The early 500SEC's also used a SLIGHTLY heavier duty version.
A 1989 or later 126 V8 transmission (722.350) will do the job good, or post 92 w140 500E/SEL transmission (722.370) will do the job alot better and alot more.... The SL transmission with the 119.960 engine will also work well (722.353). Faster downshifts...far more reponsive.

The stock 126 units are set up to handle 320 hp, plus some factory safety
margin built in.

 

[Francois]

Thanks again for all the information!

I shall make good use of it.

I think it would propably be easier for me to get my paws on a SL box.

Regards