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  #1  
Old 02-07-2013, 09:40 PM
chad1966 chad1966 is offline
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Default M46 proper engage/disengage of OD!

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.....
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  #2  
Old 02-09-2013, 01:55 PM
Boots Boots is offline
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Default There's a knack to it...

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...

Last edited by Boots; 02-09-2013 at 02:00 PM.
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  #3  
Old 02-12-2013, 12:47 AM
84wagon321 84wagon321 is offline
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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.

Last edited by 84wagon321; 02-12-2013 at 01:21 AM.
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  #4  
Old 02-12-2013, 11:43 AM
Boots Boots is offline
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Ah well, each to their own!

This bus has only done around 170k so the drivetrain is pretty sweet...
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  #5  
Old 02-12-2013, 11:46 PM
745 TurboGreasel 745 TurboGreasel is offline
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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.
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  #6  
Old 02-13-2013, 12:16 AM
84wagon321 84wagon321 is offline
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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.
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  #7  
Old 02-26-2013, 08:24 PM
RedArrow RedArrow is offline
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Vehicle: 1986 Volvo 745 TD
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Default M46 Overdrive relay, 5th gear

My 745 d24t has the m46 transmission as well. Today I started the car, idled for about 10-12mins then drove away slowly. I have to mention that my overdrive (5th gear) usually does not work until I drive for about 2miles/or 5-8-10minutes and then it functions normally without any issues… Absolutely no problems thereafter. (I know it from a good source that it is normal for an older m46 to engage later).Today as I was driving home with a relatively cold engine and I was waiting for the tranny to `warm up`. As always, after a couple of minutes of driving I tried to switch into 5th but it did not happen. I tried again a few times and the system warmed up by then so it engaged nicely as it always does. Then I drove another few miles with no isssues at all, like everything was normal and THEN I had to slow down because of traffic and I switched back to 4th and then to 3rd (traffic). This time I saw something I never experienced before in this car: the 5th gear`s green light was ON and the tranny was in 2nd or 3rd I think. Not sure though. ...I said: how? And then took it out (pushed the overdrive button on the knob and continued driving but when the next time I needed the 5th gear again, it did not work anymore. As I was trying and trying, I even heard a click coming out from the dash (as I pushed the button). Also, it clicked by itself but 5th gear never came back to life. I heard that click (or tick), click, every 2-3 seconds for like half a minute and then never again. Do you have an opinion about this thing? I think my overdrive relay went to heaven. I did not have the time and patience to do major research at 11pm but I did check the fuse (#12) and it was alright. I don`t think that my knob is malfunctioning btw. The wires inside are in ok condition and the knob is not loose so the connection is good.
Things to know about my m46 OD: 1, it always needs some time to work but then it works perfectly. 2,if the gear shift (=the stick)is pushed to the left when car was in 4th, OD disengaged by itself (sometimes IF passenger or vibration pushed the shifter a bit towards the left) 3,My OD green dash light (5) never came up in gears other than 5th but today it did once, I believe. 4, I never noticed this click-by-click sound before, coming from the dash, middle area, maybe. Like my od relay was on-off-on-off a number of times but my od green light never came on again and I had to drive home in 4th gear (40mph @ ~2000rpm)
I do clutch when using my OD, up and down too. I was suggested to do so but on the other diesel m46 Volvos I had I never did and they were all fine for long long years. Now I do clutch when switching in and out of 5th. I don`t think an OD relay would cost more than 50-60bucks but I might be wrong.(The click click noise is gone, disappeared but still no 5th gear...)I am not sure if the relay can be/should be heard when driver switches into /out of 5th gear. I remember that in my d24 240 it was possible to put the car into 4th and then press the OD button and the green 5 would come on immediately even if the engine was NOT running. I can`t do this with my d24t 745, just curiosity...is that normal that when I put the 745 m46 into 4th and then switch 5th, with engine off, the 5th dash light would NOT come up. ?? Just wondering...

Last edited by RedArrow; 02-26-2013 at 08:35 PM. Reason: Additional info
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  #8  
Old 02-26-2013, 09:11 PM
Boots Boots is offline
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I would say there are a number of things you need to check...

The delay in operation when cold would suggest to me that a fluid and filter change would be a good idea.

If the select button is sound, as you suggest, the relay may be at fault but 'in the 4th gear switch' on the main gearbox also needs to be checked.

My 740 will show green 5 and both the relay and the solenoid on the OD will click in and out with just the ignition on (i.e. motor not running) so long as the stick is in the 4th gear position.

You need to methodically work through the suspects testing each one, starting with the electricals.

One way to check if the 4th gear switch on the main box is duff is to have the ignition on, keep the OD button pressed and then move the stick into 4th and waggle it around some. If the green light/OD solenoid flicker in and out as you waggle, the 4th gear switch will need replacing.

If you can't get any green light/OD solenoid activity at all then the relay or wiring/fuse/earthing is likely the problem. Poor contact where the relays plug into the fusebox is a common problem on older cars and it is self exacerbating. A poor contact presents high resistance to the circuit causing excessive heating of the contact. This heating increases the resistance due to tarnishing/distortion and so on until eventually the contact burns out. It would be worth checking the seating and condition of the contacts on the OD relay in the fusebox.

This circuit should be reasonably easy to diagnose logically with a multimeter or test lamp...

Last edited by Boots; 02-26-2013 at 09:19 PM.
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  #9  
Old 03-04-2013, 05:58 PM
RedArrow RedArrow is offline
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Vehicle: 1986 Volvo 745 TD
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Default Tranny fluid in m46+ OD issues

Thanks for your ideas on fixing my OD. You are absolutely right about the relay-fusebox connection. I inspected the relays and many of them were not tight at all. Huge amount of dust as well. The od relay is out by now, it will be checked very soon and if not bad, I will move on to changing the fluid and inspecting all wiring I can reach around that area and also the shifter/knob itself. The delayed operation in my m46 was always present but no issues related to that at all, I think. I`ll see how it goes after spending some time with it.
Hey professional d24t owners, what is the best/suggested type of transmission fluid for an m46 tranny?
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  #10  
Old 03-05-2013, 06:39 PM
RedArrow RedArrow is offline
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Thumbs up OVERDRIVE RELAY to be tested

Quote:
Originally Posted by RedArrow View Post
Thanks for your ideas on fixing my OD. You are absolutely right about the relay-fusebox connection. I inspected the relays and many of them were not tight at all. Huge amount of dust as well. The od relay is out by now, it will be checked very soon and if not bad, I will move on to changing the fluid and inspecting all wiring I can reach around that area and also the shifter/knob itself. The delayed operation in my m46 was always present but no issues related to that at all, I think. I`ll see how it goes after spending some time with it.
Hey professional d24t owners, what is the best/suggested type of transmission fluid for an m46 tranny?
I forgot to include my other question. How would you test if the overdrive relay is functioning or not?
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