I just replaced my m47 with an m46 (bad bearing in m47), and my car seems to feel toatally different. The shift indicator points are way out of wack now, and the engine seems to be running at a lower rpm at a given speed. From the specs I have the gear ratios are the same for M46 and M47 except for 5th vs overdrive. In overdrive it is only turning just over 2000 rpm at 100km/h (60mp/h). That seems really low. I am pretty sure my 84 turbo (away for the winter so I can't check) was turning about 2450 at 100 in OD last time I drove it, and you could shift into OD at 70 without lugging. The OD on my 89 lugs below 90.
Am I missing something? I thought the rear ends were the same between all standard sedans. Were all m46s the same?

Jessie,

I drive my M46 (84-242 GLTi) a bit different than my M47 (89-245DL). The M46 seems to perform best going into OD above 50MPH (55-60 better stiil)...I'm in the habit of lifting off the throtle as I button push in OD. At 60 +, (tach will drop from 3400 to 2400 +,-) and back on throttle when OD sets (reverse action on downshift, plus engage clutch). The OD is useless under 50MPH...just won't set . As far as pull power on up grades, mine just doesn't want to. Holds it's own...put very little pull power. I plan to rebuilt M46 come spring.

My M47 will pull in 5th as strong as the lower gears....even on up grades. I use 5th at speeds under 50 (35-40 limit). On the up grades 5th pulls well from roughly 2600 on up. The steeper the grade the higher I want my RPM's. We have a local steep grade with a sweeping left hander (up hill) that the M46 has to drop to 4th to power through... the M47 will power through and continue to pull. In both I enter the sweep around 3200 with a progressive throttle.... the M46 bogs..... the M47 pulls.

Gas mileage is also best with the M47......consistent 29-31. Best from the M46 is 26-28.

Have a Happy New Year.....

Al

Thanks, it sounds like you find the m46 bogs down at about the same speed. The difference in fuel economy is probably not comparable. My 84tic sucks way more gas than my 89 dl, probably due to the lower compression engine and my lead foot. It sounds like the actuating seals are gone in your OD won't shift below 50mph. The new M46 in my 89 shifts in at 35mph no problem. Unfortunately the seals in my 84 are really shot, and the OD won't even stay engaged at 70mph. Thats my spring project.

Hey, thanks ! Never thought of the M46 as having a problem (OD not engaging below 50), I figured that was the way the M46 worked.

If the weather stays as it has been....spring projects may begin sooner than later.

I did exactly this swap on a 93 5 years ago when I bought the car. I did it just because I prefer overdrives - I love being able to slip into "5th" gear just by flicking a switch, rather than using legwork and that clumsy diagonal gearshift from 4 to 5.
I am mystified by your observations. My experience was that the ratios on the gears 1 to 4 are undetectably different (4th is straight through 1:1 in each case, as someone onserved), but that the M46 O/D ratio is slightly higher. It does 50 mph at 2000 revs.
I don't find it lugging in overdrive at all. I usually change into overdrive at about 40 mph unless I want to accelerate hard. It will take gentle hills in O/D too.
I more recently acquired an 89 with an M47 box,and it feels just like my M46 apart from the top ratio difference.

You could settle the question by doing some experiments. Jack up one rear wheel, free off the handbrake, put it in each gear in turn and count the number of engine revolutions necessary to rotate the drive shaft one complete turn.
Then repeat on the old box, if you still have it.

"rather than using legwork" Aren't you suppose to depress the clutch pedal to engage and disengage the overdrive? I asked the question when I first got my '86(M-46) and was flooded with responses.I know you don't have to but I thought it added to the life of the OD.to use the clutch.
--
philvo '86 245 215k,'90 240 196k,'87 SAAB 900 SPG 213k

On my '80 245DL, I do what it says in the instruction book:

When going into OD, I flip the switch with out using the clutch.

When going out of OD, I use the clutch.

Never had a problem with this OD or tranny in over 250K miles... (While the car is at 423K, the tranny was replaced when the car was around 150K miles...)

Ryan,
The 1986 Volvo 240 owner's manual states...."The overdrive can be engaged in only 4th gear. Depress the clutch fully when engaging and disengaging."
Maybe it was different in 1980(my '78 265GL had the slide switch)but the "newer" models are suppose to use the clutch when engaging and disengaging overdrive.
--
philvo '86 245 215k,'90 240 196k,'87 SAAB 900 SPG 213k

Thanks for the replies, I am thinking there may be something wrong with the new gearbox. The overdrive makes an oscilatting vibration sound below 80 km (about 50 mph), and I feel a bit of vibration when accelerating through the gears. It is smooth as silk above 90 though. It might be a mount problem. I think they put the m47 rectangle mount back on, and the m46 mount is round. It may be a clearance or stiffness of the mount issue.
You don't have to use the clutch to shift the overdrive but using the clutch should increase the overdrives life span. The overdrive actually has an internal "cone clutch" that locks the sunwheel when you shift, and like any clutch it does wear out. So by taking the stress off the OD when engaging it should increase the life of its internal cone clutch. From my understanding Volvo no longer supplies replacement cone clutches. Its not a huge issue where I live because 240s rust out long before the cone clutch wears out.

I know the book says one ought to use the clutch, but I know of lots of people who never realised this and find the advice surprising. I have to point out that this overdrive is used on many other cars, ane no other manufacturer advises use of the clutch.
eg, my Triumph 2000 also has the overdrive. It works on 4th and 3rd (and in the Triumph TR6 on 2nd too) and the engine puts out a lot more torque than the Volvo.

I change into and out of overdrive much as I would if forced to do clutchless ordinary gearchanges. If engaging O/D I ease off the throttle to let the revs fall as the O/D bites, and when disengaging I keep my foot on the pedal a bit to let the revs increase. With practice the jerk in either direction is virtually unnoticeable.

BTW the overdrive was not made by Volvo, but by Laycock de Normanville. As far as I know all spares are still available for all models. There are plenty of overdrive reconditioners and exchange specialists here in England, who routinely service much older versions than used on the Volvo.

It is good to know you can still get the cone clutch. I was thinking where I read that you could not. It was the IPD catalogue: "If you find it's bad (referring to the cone clutch) you will have to scrounge up a used one as they are no longer available from Volvo and are difficult to reline".
I was kind of surprised when I read that, since as you said, Laycock overdrives have been used on quite a few cars. But I though IPD was quite a reliable source of info. I have not had a cone clutch fail so I have not had to look for one yet.
I must admit I have rarely used the clutch in the past to shift the overdrives in my 240s, but in theory doing so should increase the lifespan of the cone clutch. So if someone was trying to take their 240 into the million mile club using the clutch would probably be a good idea.

Are you making the comparison in the same gear on both boxes?
Both are a one to one ratio through the box in 4th gear, the separate overdrive unit on the M46 has a slightly different ratio to the overdrive fifth gear in the M47.

Colin.

Yes I am comparing in the same gears. I think it is mostly the overdrive vs 5th gear that seems really different. Like I said I the engine is only turning about 2000 to 2100 rpm at 100. But I am also comparing it to my 84 240 turbo, and I am pretty sure it turns a little over 2400 in overdrive.

Don't you need a different Drive Shaft? check out my previous post.

http://www.brickboard.com/RWD/index.htm?id=728266&show_all=1

I was considering doing a swap, but not anymore.

Yes you do need another driveshaft. The M46 shaft is shorter, and has a different flange at the gearbox. My switch was not optional, the m47 was getting progressivley noisier, and low mileage m47s are hard to come by. It will be interesting to see if I get better mileage on the highway with the lower rpm

I was asking if you swapped the DS's. but it sounds like you did.

M47 does not have OD at all.
other gear ratios are the same on both transmissions.
what about speedometer sender?

The spedometer was not affected by the switch because it is electonic with the sender in the rear end. The M46 I put in was not punched through for a mechanical speedo anyway.
Actually the m47 does technically have an overdrive. I am pretty sure overdrive means over the 1/1 ratio. 5th gear in an m47 is in a second gear box bolted to the back of the 4 speed gearbox, just like an m46. The major difference being that the M47 is manual and it set up to seem like a true 5 speed.