posted by
someone claiming to be 1980 Volvo 245
on
Wed Nov 1 05:08 CST 2017 [ RELATED]
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Have an M46 with O/D.
In 1st gear get a shudder on start up
At city or highway speed when I accelerate to pass - the revs increase and their is slippage.
How do I know if it is the Main Clutch or O/D issues - it will slip in 2nd, 3rd and 4th gear.
O/D works well overall at highway speed.
Have done engine and tranny mounts - U-Joints and hanger bearing - no change
Any IDEAS??
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posted by
someone claiming to be cdcrawford
on
Wed Nov 1 05:26 CST 2017 [ RELATED]
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Have you ever replaced the (main) clutch? How is the pedal travel? Where is the engagement point - does the clutch start grabbing right away as you ease off the pedal, or do you have to release the pedal a fair distance before it starts to grab?
When you engage the overdrive, is there a delay? Does it ever disengage on its own, or slip in and out of overdrive?
The shudder in 1st could be oil on the clutch disc or a slightly warped disc and/or flywheel. I am inclined to think the slipping is also your "main" clutch, but it would be hard to diagnose for sure without driving your car.
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hi cd and volvo sages- now wait a minute. i obviously need some education here. never fooled with an m46 od trans but understand it works like the old borg warner semi automatic electrically actuated overdrives, common in american cars from the 30s through the 60s. the m47 which i have in my 92 is unlike the m46 in that the od is simply an actual 5th gear shift with no semi automatic actuation. the m47 has no od clutch and i dont think the m46 does either. think the 46 has a solenoid which senses the engine speed and when you let off the gas at that speed(usually about 28mph) , the solenoid pulls in the od gear which is a planetary setup behind the regular trans. any clutch slipping in either trans would be the main clutch in the bell housing. am i correct or up the creek(stinking creek) w/o a paddle. thanks tons oldduke
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oldduke--you are correct about the Laycock OD being similar to the old BW overdrive-my brother drove a '53 Studebaker--stuck in OD the whole time he had it. The actuation of the Laycock is different in that it incorporates an electric solenoid (limited by Volvo to 4th gear only--some other manufacturers allow OD in 2nd, 3rd and 4th). The electric solenoid directs hydraulic pressure (there is a pump running off an eccentric shaft) to two pistons which exert pressure to a conical clutch which engages the planetary gearset--resulting in OD.
Others have suggested the slipping is a problem with the main clutch and I'd agree 100 percent. -- Dave
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hi heck- good analysis. wasnt sure if the m46 used an electric solenoid . didnt realize it employed a hydraulic pump too. the old bw ods which many of the 50s/60s cars employed actually used a centrifugally actuated speed sensor so as to not to shift up to od if the engine speed was too low(lugging). this also employed a split second ignition interrupter wired to the coil as a sensor which allowed the upshift to od without torque load unless you locked od out with the pullout t handle under the dash. studes used this trans too which i think was the chevrolet bw model. interestingly in these old american cars you could actually obtain 6 speeds forward if you skillfully worked the clutch, throttle and t handle to go into and out of 1st, 1st od, 2d, 2d od, 3d and 3d od. but you did have to get up to 28mph in 1st to use the od mode in all three gears. most 3 pedal cars then had 3 speed transs with column shifts. the m46 od must have had some kind of lockout which limited od to 4th gear. the only american car i saw which had the manual trans laycock od (denorman) was the later model amc gremlins and hornets in 74. last use of the bw od was about 68 in american cars. thanks tons oldduke
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posted by
someone claiming to be cdcrawford
on
Wed Nov 1 14:08 CST 2017 [ RELATED]
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Oldduke,
The M46 is really a 4-speed transmission (M45) with an output shaft tailored to accept the Laycock overdrive that is bolted up to the back of it.
The overdrive is a single-speed automatic transmission, if you will. It has the planetary gear set typical of an automatic, including a cone clutch. Power is transmitted through the cone clutch at all times, even when the overdrive is disengaged. A "bad" cone clutch can cause slippage, but there are usually other symptoms as well.
There is a momentary contact push-button switch in the center of the "H" pattern on the M46 shift knob. This switch is grounded by the so-called "4th gear switch" that locks out OD in 1st through 3rd and in reverse. When you push the button in 4th gear, a relay behind the dash energizes the solenoid on the OD unit. The solenoid opens and allows fluid pressure to engage the OD gear. The pressure is generated by the output shaft of the transmission, and I believe you have to be going something like 30 mph at minimum to generate enough pressure to engage OD. (Although, as a practical matter, 30 mph is 3rd gear range on the M46 and you will "lug" the engine if you engage OD in 4th at any speed below about 45-50 mph due to the tall 3.31 rear end in these cars.)
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Does the 1980 M46 use the slide switch on the gear lever? If it has the push button, the OD relay gets a 12V signal (not ground) from the momentary contact gear lever push button, and if - and only if - the relay's pin No. 85 is grounded via the 4th gear switch on the transmission, it then activates and supplies 12V to the OD solenoid. Another pulse from the button or a shift out of 4th and the relay trips off, OD disengages.
Heat affects everything, and my M46 OD will shudder after about 20 minutes of driving on hot days if you let the car speed get below about 50-55MPH. No problem in cool weather. This is related to the fluid viscosity and the leakage of the 35-yr-old seals on the OD pistons once the fluid gets hot and thins out. At higher speeds the pump can keep up with the leakage and the OD works well.
A possible cheap fix for the original poster (assuming his OD is slipping) might be to drain and refill the trans and OD (and clean the OD screen and magnet) with the proper fluid, ATF Type "F". Worth a try. A new gasket for the OD sump cover will be needed....IPDUSA.com; item No. 106302 at $9.45.
I had an MGB with the same style Laycock OD used by Volvo. It would engage the OD in 3rd or 4th via a pull (on) or push (off) on the windshield wiper stalk. Great fun on twisty roads toggling the OD instantly on and off in 3rd gear between corners.
--
Bob: Son's XC70, my 83 244DL, 89 745 (Chev LT-1 V8), 98 S90 (recently sold) and XC60. Also '77 MGB and four old motorcycles
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posted by
someone claiming to be cdcrawford
on
Wed Nov 1 21:27 CST 2017 [ RELATED]
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I could be totally off base here, but the OP mentioned that his car "shudders" in 1st gear and it feels like the clutch is slipping in 2nd, 3rd and 4th. This could be a bad cone clutch, but my gut feeling is that his "main" clutch is fried (or very badly glazed from a rear main seal leak) and needs to be replaced.
Your shudder in overdrive below 50 mph....do you know your rear end ratio? 50 mph is about as "low" as I would engage overdrive in my '84 with the 3.31 rear. At 50 in 4+OD it is turning just under 2,000 rpm. I wonder if your shudder is just the engine lugging?
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If you replace the fluid you should at the same time clean under the overdrive access cover.
This M46 has 2 magnets and 2 strainers.
- one magnet at the drain plug
- one magnet in the access cover
- one rectagular strainer over the magnet
- one cylindrical strainer below the largest round cover(if I remember well ) over the access cover. It has two holes and can be difficult to unscrew but it is the most important one to clean, very fine screen mesh.
I used two pushers held with one hand and a flat screw driver to pry in between. I eventualy made my own tool for this job.
Tell us what you find.
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hi od sages- the history of the m46 style od is interesting. the bw ods usually had a speed sensor which kicked out the od back to direct when the speed dropped below 28-30. the od ratio in the bw was usually .73 which is 27% over the drive ratio. if the volvo with the laycock had a 3.31 diff ratio and its od ratio was i think .80 that would give you a final drive of 2.65 which gives you much beter mpg and less engine wear, but would lug the engine below 40mph. this is exactly how my 92 245 works with the m47 which i think has the .80 od ratio like the m46. the upside is it pumps 25 mpg around town and 30 on the interstate. pretty good for a heavy car like the 245. highest final drive ive seen is 2.15 in od(.73) in a slantsix duster with a diff gear of 2.94. only down side is bad words and hand gestures from fellow drivers exasperated with my slow launches and sluggishness. seems im always nursing hurt feelings. think the m46 od and the bw od were trouble prone which is one reason they were dropped in favor of a full manual shift into od like the m47. phattest regards oldduke
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posted by
someone claiming to be cdcrawford
on
Thu Nov 2 11:04 CST 2017 [ RELATED]
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Oldduke,
Yep, the OD is really not even necessary on a brick with a 3.31 rear, although it is nice to have on long highway trips. But because of the tall rear gearing, in 4th gear with the overdrive OFF the engine is only turning about 3,200 rpm at 70 mph. Overdrive drops it down to about 2600 rpm. The difference in fuel economy (having driven my 245 with a bad OD solenoid and thus no OD for several years) is on the order of 2 mpg. Not very significant. What is significant, though, is how much quieter the car is at cruise with the OD engaged.
I am not really sure why Volvo used an OD (instead of a true 5 spd) up to 1987. My guess is that they had a surplus of M45 4-speed transmissions in a warehouse somewhere and it was more cost effective to adapt the driveshaft to take an already "provden" and readily available OD unit, than it would have been to design a new 5-spd tranny. But the OD is not reliable over about 100-120K miles. My solenoid died around 120K. Finally replaced it several years later at 200K when I had the extra funds. Have also gone through a few relays, push buttons, and "4th gear switches." It is not an inherently bad design, but it does not hold up well on a car that is known for doing 300-400K miles.
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IMHO nothing beats a 4 speed tranny with a Laycock OD. With a 5 speed the clutch has to be used to go in or out of 5th gear. With a Laycock OD, you can shift in or out instantly at any speed or throttle position and they are bulletproof if you make sure they always have enough reasonable clean oil. Sure, with high miles, you may have to replace a switch or solenoid, but that beats replacing an engine clutch. Tom
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IMHO nothing beats a 4 speed tranny with a Laycock OD. With a 5 speed the clutch has to be used to go in or out of 5th gear. With a Laycock OD, you can shift in or out instantly at any speed or throttle position and they are bulletproof if you make sure they always have enough reasonable clean oil. Sure, with high miles, you may have to replace a switch or solenoid, but that beats replacing an engine clutch. Tom
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IMHO nothing beats a 4 speed tranny with a Laycock OD. With a 5 speed the clutch has to be used to go in or out of 5th gear. With a Laycock OD, you can shift in or out instantly at any speed or throttle position and they are bulletproof if you make sure they always have enough reasonable clean oil. Sure, with high miles, you may have to replace a switch or solenoid, but that beats replacing an engine clutch. Tom
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posted by
someone claiming to be cdcrawford
on
Thu Nov 2 12:23 CST 2017 [ RELATED]
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I can appreciate that. But beginning somewhere in the mid 80's, Volvo advised, in the owner's manual, to use the clutch when shifting in and out of OD. Supposedly, it reduces the "shock" on the system when engaging OD and the OD will last a little longer.
I've always used the clutch when shifting into OD and got 250K out of the original, factory clutch in my 245 and 280K out of the original clutch in my 244 (both M46 cars). The clutches in these cars are "big" relative to the power output of the engine and seem to last a very long time given sensible driving habits.
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posted by
someone claiming to be 1980 Volvo 245
on
Wed Nov 1 10:58 CST 2017 [ RELATED]
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Thanks to you all - very helpful
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