240 auto to manual diff options

pigdog

Hey guys so the m46 manual conversion is complete and car is regoed and being driven daily but i need to look at rear end options to bring the revs down as i do a lot of hwy runs
.
i do enjoy how quick she gets up and goes off the line but my fuel economy is suffering on long trips , it sits on 3000rpm at 100kph , i haven't got the overdrive connected yet will be getting onto that in the next week or 2 so that should help on the hwy but i would still like to bring it down abit more ive got several extremely long trips coming up .

now i haven't really looked into the rear end much yet so dont know what options i have , obviously swapping in a manual center would change the ratio , there is a manual 240 at a local wreckers near me , is there any differences between centers depending on year? mines a 1990 model and has the speed sensor in the diff , pretty sure the 240 at the wreckers is an 88 maybe 87 i cant recall .

Ive also briefly read a couple things on using a jeep Cherokee lsd center .... how much work is involved in that swap, what needs to be done and is it a feesable option?
i always see cherokees being parted out and think a mate actually has one so i could prob source the center for cheap

i really would like a lsd in the rear ive been looking at lockers and have considered welding mine up but im getting too old for fully locked diffs in a daily ive done that many times in previous cars now ive gotta drive my daughter around and dont feel like skipping and carrying on around every damn roundabout and parking lots ..

so yeah thats where im at just need to know my options really.

cheers guys
here is a pic of the old girl if you haven't already seen it .

Dauntless

Not too sure what gear ratio you currently have, but it sounds like a 4.10.

I'm 90% sure I have an entire 3.54 1031 diff you can have cheaply. It won't have the speedo drive, but you could swap the ring and pinion while you're fitting the LSD of your choice.

Vee_Que

It's possible it's a 3.73 with the auto. And you just have shorter tyres then stock, 3500 is what they rev at With a 4.1 at 100kmh. But it could already be a 3.54 given its auto. Manuals had a shorter ratio.

Get the od working, that will get it down to 2500, but jeeps use the same diff as volvos do on the front. Which don't have an lsd. The options are a Detroit style locker or eaton lsd, price difference of $500. With good grippy tyres a locker will behave well.

Keep in mind the earlier diffs may not be fully compatible to swap around.

Dauntless

Ah, if the OD is not working, just fix that. 3000 in 4th will be about 2400 i'm OD.

jamesinc

@pigdog can I feature that photo above on Oz Volvo's Facebook page?

Spac

86+ factory manual 240s had 3.31 diff gears.
Lovely on the highway, but annoying around town - mostly because you have to go back to second gear when you think it should pull third. Also won't pull top gear in 50kph zones if there is any sort of uphill.

egads (she/her)

Dauntless;133283 wroteAh, if the OD is not working, just fix that. 3000 in 4th will be about 2400 i'm OD.

Start with this for sure. Could be as simple as non O/D fluid in the box

pigdog

jamesinc;133289 wrote@pigdog can I feature that photo above on Oz Volvo's Facebook page?

Yeah mate go for it .

Dauntless;133283 wroteAh, if the OD is not working, just fix that. 3000 in 4th will be about 2400 i'm OD.

Ok sweet ill get the overdrive going (hopefully) and see how it feels and go from there .
its just not wired up at the moment i need to redo its wiring cause its horrible and get a relay it wasn't wired up in the car i pulled it from either so ive never seen it work my main concern was getting the car on the road then dealing with overdrive
i just put new type f fluid in the box the other day so that should be sweet ,
i can live with 2400rpm at 100 so if thats the case i wont swap the diff for a manual one i do enjoy the auto diff for everything except the hwy runs .