M46 proper engage/disengage of OD!

[chad1966]

Ok this is my first Volvo as you may know and my first experience driving a car with a elec OD. When I shift into OD should I be pushing in the clutch like a standard 5th gear, shift while letting off the gas pedal, or just keep accelerating and let it shift. Now on down shifting has me baffled. Should I be clicking OD off before down shifting at all? While on the freeway today I was in OD and hit traffic, I slowed down enough to grab third and while not realizing that OD had not dis-engaged because I had to pay attention to the vehicles in front of me. I had to hit the button again and then it dis engaged. Am I just over thinking this or is there a proper in/out procedure for OD. Thanks.....

[Boots]

I'm no authority on this but the following is how I drive the OD and it seems happy enough!

You shouldn't depress the clutch when selecting or de-selecting the OD, it has its own 'clutch' internally.

The main gearbox should have a switch that only allows the OD to be selected in 4th gear and automatically de-selects it if you move the gear lever out of that gear. (700/900 only???)

When selecting or de-selecting the OD, momentarily lift the throttle to the point where the engine is no longer accelerating or braking so that there is minimum strain on the drivetrain whilst the OD engages/dis-engages. Then re-apply throttle or release completely depending on whether you desire acceleration or engine braking.

The throttle action you want is pretty much identical to that which you would perform changing between gears in the main box, except there is a short delay between pressing the button and when you need to lift your right foot.

I find this delay depends on road speed. At 30mph it can be nearly 1.5 seconds. When thrashing flat out at 70mph the whole sequence from pressing the button to getting back on the throttle takes less than half a second.

At low road speeds (below 40 mph say) with the engine braking, I feel that the forces involved are low enough to not touch the throttle at all when de-selecting the OD. It just gently disengages, the revs rise a bit and you get some more engine braking.

Once you get the hang of where to put the throttle when, you can get the changes so smooth your passengers won't even know they've happened.

Have you ever tried changing up and down a manual box without using the clutch? If so, you'll know what I mean by 'matching' the revs. This is what you want to be doing to give your OD an easy life...

Although the 4th gear switch will dis-engage the OD when you shift down, I don't usually rely on this as, on my box, going straight for 3rd from 4th + OD catches the synchromesh on 3rd out, eliciting a fairly good crunch! If I know I'm gonna want 3rd next (approaching roundabout/traffic etc.) I de-select the OD a couple of seconds before changing down.

All this said, I get the impression that this OD is a pretty sturdy beast and will stand up to a fair amount of abuse. I occasionally have brain fade and press the button at silly times or forget to lift off the gas and it seems to survive!

Now I've got used to it, I really love my OD - its really satisfying when you get it just right...

[84wagon321]

HELLO- I have 2 1984 D24 powered wagons. One shifts more smoothly than the other (probably an age and wear factor).
Frankly, I prefer using the clutch when going from 4th to OD as if I were shifting a 5-speed w/o overdrive. It is guaranteed smooth and insures a good clean shift, especially if timed correctly.
My OD kinda 'klanked' in on the first wagon purchased. I thus resorted to using the clutch to completely eliminate that issue. Again, there may be some age and wear factors here at 300k! The OD unit may be a bit sluggish due to this. The uni-joints, intermediate bearing, and differential may also be a bit 'loose' and on the worn side.

The second wagon shifts much smoother overall. I have not tried to go from 4th to OD "straight with the button only" to see if it is better than the other one. Bottom line for me is to use the clutch. I'm quite happy with that.
I will be driving this vehicle tomorrow and will post if it is silky smooth or no.

Downshifting is usually with the clutch as well since it enables me to go directly into the lower gear of choice. Going from 4th w/OD into neutral and back to 4th puts you in 4th of course. Same is achieved by merely pressing the button. I use the clutch because many times I want out of OD and want maybe 3rd or even 2nd on the exit ramp (after braking and a bit of a coast). If the light turns green before I reach it my momentum and 2nd gear are usually the ticket.

I lean towards 'kid glove' treatment of my vintage wagons so I can continue to enjoy a great ride and 36 mpg on my daily commute between Tacoma and Seattle.

My '87 automatic gasser shifts into OD quite smoothly going both ways but that is to be expected.

Perhaps someone with a tighter drive train will chime in and offer more thoughts.

[Boots]

Ah well, each to their own!

This bus has only done around 170k so the drivetrain is pretty sweet...

[745 TurboGreasel]

The OD has a a screen which should be cleaned at least once every 15 years, and it may engage better if you do that.
I'm of the opinion that it should be clutched on upshift if under load, but we might not make enough power for it to matter. Mine has survived may full throttle cycles.

[84wagon321]

Well I used the 'other' wagon today and it shifted into and out of overdrive very smoothly without 'clutching'. I did ease up on the throttle to go up from 4th to OD and it was sweet. Apparently the 'klanky' wagon's OD needs remediation. The screen seems like a good start since it engages in a delayed sense and all at once- 'klank!, I will continue to use clutch for it.

I would guess the smooth OD would be the norm on this application.

As previously mentioned, shifting out of 4th w/ OD engaged should automatically disable the OD. Conversely, the OD will normally engage only in 4th. If your xmsn does otherwise there is a problem somewhere.

I have had the OD continuously disengage on it own for a short period, but a new relay completely solved that problem.