7 series Auto to Manual Transsmission swap

[Eli]

Greetings,

I did some searching, but couldn't find much info on this particular swap, which I thought would be a fairly popular one. I'm sure not everyone is jumping straight to T5s. :)

The Car: '83 760 D24T ZF auto tranny.

I am planning on swapping in an M46 and ditching the ZF auto. I am wondering about the interchangeability of parts.

I know I need a manual transmission(duh), flywheel from a manual D24/T, clutch, clutch cable, and pedals. Do I need to get a different cross member and driveshaft, or are those interchangeable from auto to manual in D24T 700s?

If I need to source a M46 cross member and/or driveshaft do they need to be D24T specific?

Thanks in advance!

-Eli

[Jason]

Everything you have listed is correct. You will need the front section from a 83 760 with a M46 or the entire driveshaft from an M46 car thats '84 or later. The spline count on a '83 is different than the later ones. I did this swap with my buddies '85 with ZF and we had to use the entire driveshaft out of the donor '83. However the spine setup was the same as my '84. The crossmember is the same, you'll just be moving it back farther on the car since the trans is longer thanks to the OD unit. However you'll find the threaded inserts are already in the body! The driveshaft shouldn't need to be D24 specific, but will have to be from a 7xx series with M46 if you go to replace the whole thing or just the front section if you can find one from an '83. Another option is to just have it shortened. My local driveshaft shop only charged me $70 to shorten mine which included installing the T-5 slip yoke and a new U-joint. Might not be worth the trip and headache at the salvage yard...

Jason

[piper109]

You will have to make sure you have the right bellhousing on the M46 too as if you use one from the non-turbo D24 setup if will be wrongly "clocked".
I found it necessary to use the M46 crossmember but seeing as I had it , I did not try to use the one from the zf. You will also need the gearchange lever boot and soundproofing surround and a way to switch the overdrive on and off. I made my own circuit for that as I had trouble finding the correct relay.

Bear in mind too that the rear axle ratio off the auto car will have a 3.91 ratio as compared to 3.54 with the normal manual and the car will run higher revs. More fun though :-)

Steve

[Jason]

Yup mine had a short 1st gear with the M46 and zf rear end, though my car had a 3.73 ratio.... I don't think the 3.91 came untill later. Maybe I'm confused but I remember the cross members being exactly the same...

Jason

[Eli]

Thanks so much for your help guys.

The rear end ratio is a good point. I seem to remember something about the cross members being the same auto/manual.

As for the driveshaft, you're saying I can just take the current one out of my car and take it to a driveshaft shop and get it shortened? Of course I would need the measurement to tell them, but that would be it. No sourcing stuff?

Thanks again.

[Jason]

As for the driveshaft, you're saying I can just take the current one out of my car and take it to a driveshaft shop and get it shortened? Of course I would need the measurement to tell them, but that would be it. No sourcing stuff?

Thanks again.

Yes.


The output flange on the M46 is the same as the zf, so a shorter driveshaft is all you'll need. The different ratio will make it a little more fun to drive especially around town. I doubt the highway mileage will suffer much. If you want to make it like the stock setup, 3.55 rear end gear sets sell pretty cheap as most guys want the shorter ratios. Look around on Turbobricks for a set if you decide to go that route.

Jason

[v8volvo]

What went wrong with your ZF? The ZF trans works really well with the D24T, they are matched to each other very nicely -- in some ways better than the M46 setup. If I had a ZF failure I would rebuild it rather than swapping to M46 -- easier, cheaper, keeps car original, and IMHO just as nice to drive (perhaps even nicer if you drive in city traffic, as I do). In my mind the main advantages of the M46 over the ZF are all related to practicality rather than driving experience: I prefer to use a ZF-equipped car as my daily driver, but for long distance road trips that take me far from home I use a car with a manual transmission because of additional options a manual transmission provides in the case of battery/starter/glow system failure, elimination of ATF lines and cooler and associated complexity/fluid maintenance/cooling load, and etc. If I were choosing purely on which I liked driving better, in most situations I would choose the automatic.

However, I can probably point you to a source for all the conversion parts if you do want to go that way. Where are you located? Last I checked, Mike Rausch in PA (member "Volvoist" on this forum) had everything you would need, incl trans w/ correct bellhousing, pedal setup, cable, flywheel, etc. Contact him if you are interested. If you can't reach him through the forum PM me and I will pass along his info.

Last thing -- not to be particular, but if your car is an automatic, it is not an '83... 1984 was the first year for an automatic option in a 700-series diesel. Diesel option in the 760 was discontinued after 1985, so yours must be either an '84 or '85. ;-)