Which car has which diff?

[rogerthechorister]

I know that B234Fs have the 3:31 diff. Well, I've found it to be so on the only two I've checked. I've been told (well, read here) that the B230FK engines are accompanied by 3:31 diffs, which seems odd.

Does anyone know how to predict?

I've never yet found a legible axle plate, not even when I can get at the axle completely 'coz it's off the car, so IMHO that is not an answer!

[Michaeleff]

This has always been a problem with proliferation of models by manufacturers: and today, worse than ever.

So many variants.

Years back when I was racing MG Midgets amongst other cars, since it was impractical to even consider changing gearbox ratios, we would adjust gearing for different circuits by swapping out the diff.

To collect sufficient different final drive ratios meant trawling around scrap yards and collecting diffs! Luckily the A Series BMC diff was pretty ubiquitous: used on Morris Minors, A40, A35, A30, Sprite, Midget, Post Office Van (!!) and so on.

The trick was to jack up one rear wheel, make sure the vehicle is in neutral (or not park if auto) stick a chalk mark on the pinion flange and the jacked up wheel and then turn the pinion one revolution and count the revolutions - carefully - of the rear wheel or hub.

In a perfect World (Which it aint!) Volvo Technical Services would be able to tell you right away from their core model lists and specs.

I wouldn't hold my breath waiting for that to happen: particularly after all the ownership changes.

Perhaps everyone on this forum could remember to check the final drive ratio of their own diff when carrying out servicing and we could then build up a Master List?

[RealEstate]

B230FB has 3.91 final drive

[Steve940estate]

Some of the owners manuals give the axle ratios for specific models, these change year from year, I have collected a few now. Manual or auto will effect things as well.
The only way to tell for sure is to check the label, count turns or count teeth.
My 230FB auto has a 3.91 diff and the 230FT m90 doner car I have has a 3.54.
I think I did write a list of all the ones I had found a while back.

[rogerthechorister]

B234F M46 - 3: 31
760T ZF auto - 3: 54 but it might be 3: 73 - not on road at moment so I can't check
B200FT M90 - probably 3: 73 - not on road at moment so I can't check
B280E a different auto not ZF - I think 3:54 but long scrapped.
Sport Edition seems stupid low - I'm guessing about 3: 90 but not sure until daughter gives it back Saturday.


I want lots of 3: 31s!

And torsen or locking diffs too. I might get both on a 960 or V90 (solid axle)?

[Steve940estate]

Looking at the handbooks I have the only 3.31 diffs are for the 230FK with a manual gearbox. Thats for a 95 and 96 car. I have another 95 handbook that doesn't list the 3.31 at all. I wonder if 95 was the year they introduced the FK though.

As a guide you need to be looking for cars with more torque or those intended to do a few more mpg. FT's were 3.54 to make them a bit quicker. I wonder what later turbo diesels had ?
If everyone who knows their axle ratio could post it here with the spec of their car some sort of table could be made up.
I tried to do something similar with the suspension codes to try and find out a bit more about what springs etc were fitted to what models but didn't get much help.

I'm running a 3.91 on my FT at the moment and it goes like stink, but only if you rev it a lot. Better bet would be the 3.73 or go to the standard 3.54. I can't see much point apart from increased fuel economy going more than that as you can't go more than 70mph anyway.

[gpl1968]

My B230FK / M90 is 3.54

[rogerthechorister]

Face it everyone clears "national" by about 10 mph and I like the 3:31 as I'm barely ticking over at about 2,200 rpm or 2,300 rpm and I can drop two gears to third if anyone annoys me. Last time I did that to two volvos in the outside lane in convoy the second one turned out to be a lemon curd sandwich - moi, ossifer?

[Steve940estate]

Originally Posted by gpl1968

My B230FK / M90 is 3.54

Typical, there isn't any way of telling. I take it thats a manual, what year ?

There are different M90's available as well (not sure how common they are though)

Does it have a diff lock, perhaps to keep things simple the diff locks were only fitted with 3.54s as most were fitted on the ft. Again just a guess but there must be some logic to it.
I was pretty sure that a fk I got my 2nd gearbox from was a 3.7 so that makes three diffieent ratios fitted to the same engined car.

Oh and the 70mph was just an official comment. My car is doing about 3000rmp at that speed so you can just floor it without changing down. Lazy but it makes motorway driving very relaxed. I've still seen an indicated 120mph on my private teat track which is fast enough really. I'm going to swap the axle to try and save a few quid on petrol though.

[davebslater(uk)]

the main difference is between auto/manual .

the autos have 3.73/3.91 ZF or AW depending .

most manuals are 3.54 , my FK is 3.54 .

the reason being the autos have a long first gear , so its an attempt to have some towing capacity .

3.3:1 you may find more on a saloon , but definitely not an auto .

interestingly in the early cars the GLE with an FB engine , ie top of the range will have a locker with an automatic box .