Volvo overdrive splice into a Mercedes Diesel
 

In the CHINA BLUE sold thread, whunter suggested splicing a volvo overdrive unit into a W123 4spd manual driveline. Anyone ever do such a thing?

It's a J type overdrive, meaning it was originally bolted to the back of some other transmission. From what I've read they grenade in reverse, and work fine in the forward gears. Activated by an electric solenoid.

No idea what models/years though

EDIT:
Here you go:

http://gtsixing.blogspot.com/2012/01/overdrive-modification_13.html

Answer
 

SOLD: 1980 Mercedes W123 240D – China blue
http://www.peachparts.com/shopforum/diesel-discussion/330520-sold-1980-mercedes-w123-240d-%96-china-blue.html


Here is what I am considering

http://www.management-advantage.com/products/ModelAFordOverdrive.htm

Model T Ford Forum: Volvo/Laycock overdrive in the driveshaft - howto?

Model T Ford Forum: Laycock Overdrive question.

Volvo Overdrive - The Ford Barn

Volvo 4 speed O/D to a Model A - The Ford Barn

Laycock Overdrive in early ford - THE H.A.M.B.

Model T Ford Forum: Electronic Overdrive

Model A Overdrive - THE H.A.M.B.

Hi-speed ring & pinion vs overdrive - The Ford Barn

Borg Warner Overdrive - Installation on other Vehicles?

"Maximum Overdrive under/overdrive transmissions the most awarded auxiliary transmissions for all applications manual and automatic for classic automobiles, street rods, racing, motorhomes, trucks, trailers, RV's, and custom applications."

Shift into Overdrive | Hemmings Motor News


.

You are going to have to get a mainshaft that is longer by the width of the Laycock unit. Is that going to be easy or cheap?

A driveshaft shop should be able to shorten/lengthen anything you need for around $300

^^ transmission mainshaft

I'm interested in this too...

...but I've been wondering about actually doing it in reality - the biggest problem I see is how you would fit an over drive onto the rear casing of another transmission. The lengthening of the output shaft shouldn't be too difficult - but looking at the Haynes manual (yes yes I know it is crap) section on the manual transmission it looks like the clearances for the rest of the gearbox come off the back cover.

{Much like the rear end of the 722.1 automatic transmissions - get that nut on the output shaft wrong / position of the back end of the gear box wrong and everything else will be out of whack; gearbox not last long with bits in wrong place}

You wouldn't add it to the transmission-you would splice it into the driveshaft.

Trans->DS->OD->DS->Diff

the biggest question for me is room. the most amount of space available in the tunnel is immediately after the transmission, which is also where the shift linkage bars are, and would the overdrive hit them is my question. How big around is this item? would you have to enlargen the tunnel?

oh. OK. I'm thinking about how Triumph did it

Maybe it could sit right in front of the diff? IIRC it's maybe 9" in diameter...I have a few of those A and D types and have rebuilt a couple years ago.

Still think it's spendy. Parts can't be very available when the OD goes bang. An adapter plate with a domestic 5 speed is probably best long term.

Volvo started using external overdrive units in the 1960s. They were used on some

-122 (Amazon),
-1800/1800es,
- 142,
- 240, and
- 740/760 (Turbo only)
series cars.

The overdrive was activated by a column stalk on the 1960s to early 70s cars. On the 240 series and 740 it was switched to a button on the shifter. It could only be activated when the car was in fourth.

My 142 was a low-spec model and didn't have it, so I can't say if there was any provision for it to auto-disengage when shifted out of forward gear on the 60s and early 70s cars. However, the later 240/740 had a dummy switch that automatically disengaged the OD if the car was shifted out of 4th with the OD still engaged.

I am not sure if Volvo owners of the era exactly loved the system, but the old pushrod B18/B20, and to a lesser extent the later OHC B21/B23 four-cylinder engines sounded really agricultural at highway speeds, without the OD in operation.... :D

thoughts
 

The trick is that the installations in the links above show the OD in a torque tube closed driveline, as in the Model A and T. These (and many old cars up into the 50's) have a sealed tube from the back of the transmission (slip joint in the tube and a single u-joint at the trans) all the way back to the diff. The rear axle springs on these cars carry no torque, only weight. (this is partly how the 'A can use a single elliptical spring on the rear axle)

So to install an OD like this on those, you cut the outer tube, remove a section of the tube equal to the length of the OD unit, install flanges on the tube halves that bolt up to the OD unit, cut and spline the inside driveshaft to fit the unit on each end. The OD unit replaces a portion of the torque tube and carries the driveshaft torque.

I once owned an MGB that had a 4-speed manual with a similar electric Laycock OD, and this was bolted to the back of the trans, and then an open driveshaft from there to the diff.

In the Mercedes, seems like you'd have to somehow attach the unit to the trans and perhaps eliminate the center bearing (maybe come out of the OD unit with a u-joint?). If you did a divorced (trans-ds-od-ds-diff) setup, you you need to seal both ends of the unit and affix it in an appropriate way to the undercarriage, as it would be carrying torque.

Just some thoughts ... a very interesting idea.

-Dan

My Volvo has the Manual with the Overdrive. Is there any way to use the complete Transmission (a Saginaw Transmission).

Also somewhere inside is a Pump to circulate the ATF used as a lubricant.

I agree. A taller rear diff can give the cruising RPMs we all want as well.

It seems like I am not the first who thought about the volvo overdrive to a W123.
My plan is to use it after a 722.118 4-speed auto gearbox, 240D engine.
My ideas and some arrangements:
1. Bought a Volvo trans with an overdrive (waiting for delivery)
2. I will cut the tunnel from a wreck to have a test bench.
3. Found a company that will sell me the end cap of the OD - red part - (it will be a separated and sealed unit, not sharing oil with the trans) also a shaft - blue part - with the 3 screw yoke connection to the MB trans through a flexdisc, another yoke on the OD output to connect the shortened propshaft.
4. According to my measurements, the OD will fit in the tunnel, I think the biggest problem is the transmission linkage.(dimension B????)

Here are some pictures and dimensions:

http://regahifi.cz/mb/MEAS.JPG
http://regahifi.cz/mb/tunnel.jpg