850 Gearbox

Post by **manovlov** » 24 Oct 2022, 03:17

Hy Buddies,

My workshop begins to let me have enough room to work on my car properly. I have a question on the gearbox. For reminder, my 850 is from 02/1995 - Petrol - LW5502 - 2.5 L 20 V 170 HP.

The box makes a bit noise in first and second gear. I hear a crunching roll. I have in mind to extract the block engine with the gearbox and take the opportunity to replace some stuff ( gearbox, sub frame, rear engine mount, to control the steering rack, to clean the engine bay, to control rust, some paint maybe...).

As you can see on the board, my engine is not named, it only speaks about B 52XX.
What do the numbers between slashes mean ?
Which gearbox should i find to replace mine ?
A more recent GB (from 1995- 1996-1997, V70 1998) could fit ?

To refurbish the original GB would cost approximately 1300 $. My idea is to to inject this money rather in new OEM parts first, including another GB (expecting it will be ok) lambda sensor, PCV, hoses, heater core, radiator etc....).

Thanks to those who will share their knowledge.

Manov

: 850 Gearbox specificities.jpeg (311.27 KiB) Viewed 1942 times

Post by **abscate** » 24 Oct 2022, 04:02

The numbers are the rear axle ratio, or the final drive ratio in Anglais

Number of rotations coming from the gear box : a single turn of the rear wheels

A higher number means quicker acceleration ,a lower number gives better fuel economy.

You can calculate the total drive ration of engine revs to wheel revolutions by multiplying the gear ration and final drive ratio.

Your new homework…why is an automatic final drive ratio so much lower than a manual drive ratio?

Post by **manovlov** » 24 Oct 2022, 04:08

... because the automatic gearbox uses belt and no cam ?

Post by **abscate** » 24 Oct 2022, 06:08

No direct drive clutch. The fluid torque converter allows the engine revs to not match the wheel revs, unlike a manual transmission , so the rear end can be lower ratio

Post by **manovlov** » 24 Oct 2022, 08:36

Ok, i will study that more precisely. To come back to my question, as the GB is a M56, any GB stamped M56 will get then ?

Post by **scot850** » 24 Oct 2022, 10:54

On a front wheel drive car, the differential is built into the transmission. So, if you want an easier life, I would look at trying to find a matching transmission with the same ratios as yours.

I have to say I am surprised they had different ratios for the manual transmission/differential.

You could have your transmission rebuilt but I think I recall this is your daily car so down time to allow that to happen is probably not an option.

Neil.

Post by **Chuck W** » 24 Oct 2022, 11:57

I don't think there are many "repair" parts available for the M56 transmissions, at least that's what I've seen mentioned.

Post by **manovlov** » 24 Oct 2022, 22:34

scot850 wrote: ↑24 Oct 2022, 10:54 On a front wheel drive car, the differential is built into the transmission. So, if you want an easier life, I would look at trying to find a matching transmission with the same ratios as yours.

I have to say I am surprised they had different ratios for the manual transmission/differential.

You could have your transmission rebuilt but I think I recall this is your daily car so down time to allow that to happen is probably not an option.

Neil.

Obviously, it's my daily car, but i gp to work by foot. So, to have it in a garage for a couple of week is not an issue.

Post by **manovlov** » 24 Oct 2022, 22:37

Chuck W wrote: ↑24 Oct 2022, 11:57 I don't think there are many "repair" parts available for the M56 transmissions, at least that's what I've seen mentioned.

I'm afraid you may are right. But how to know this more level detail when i will buy another one ? In general, people write in their classified ad "M56", manual or automatic that's all. Where to find the precision ?

Post by **Clemens** » 26 Oct 2022, 11:46

Chuck W wrote: ↑24 Oct 2022, 11:57 I don't think there are many "repair" parts available for the M56 transmissions, at least that's what I've seen mentioned.

As it looks, the only parts available are the bearings (I have a list of them if someone needs them) and the seals. Syncro rings are not available, and nothing else.

Any M56 will fit any 850. The turbo M56s are said to have a strengthened 3rd gear according to german speed freaks. Swedespeed frequent swappers in the US claim there is no difference. But for a NA car, it doesn't really matter. One important thing though: from 96 onward the vehicle speed was calculated via ABS, before that there was a speed sensor in the tranny. So you need a 92-95 tranny for your cruise control to work.

Your flag indicates you are from Europe. If this is true, try bildelbasen.se (i hope i typed the name correctly, if not google will help) for sourcing a used tranny. Bildelbasen is a network of scandinavian junk yards, they have tons of Volvo parts listed. My m56 out of a running 96 T5M was less than 400 Euro including shipping, if I recall correctly. And this is a good price for Europe.

If you want to get the swap done fast, get a used tranny, replace the bearings and seals while you're at it (or have a shop replace the bearings for you) and then swap everything over.

If syncro rings are shot, you need to get ones out of a working M56. You supposedly can use them out of any M56.