chen@uiucdcsb.CS.UIUC.EDU (12/02/85)
The automatic transmission of my '77 Plymouth Volare is producing a
heavy thump when shifted from Neutral to either Reverse or Drive.
The harshness of the transmission engagement is roughly proportional to
the idling speed. The thump can jolt the car at cold idle speed (1400 rpm),
but is tolerable at hot idle (700 rpm). The level and quality of the
transmission fluid has been checked out fine, the idle speeds are
also alright. Other than the stated problem the trasmission works fine
(no delay, no slippage). I would appreciate any pointer
to the probable cause of the problem. Thanks.
Kaihu Chen
{ihnp4,vonvex,pur-ee}!uiucdcs!chen
chen!uiuc@cs-net.arpa
chen@uiuc.arpa
University of Illinois at Urbana-Champaignsaf@bonnie.UUCP (Steve Falco) (12/03/85)
> The automatic transmission of my '77 Plymouth Volare is producing a > heavy thump when shifted from Neutral to either Reverse or Drive. A thump usually indicates "play" in the drivetrain. The usual cause is a worn universal joint in the driveshaft. These are pretty easy to change if you have access to a large enough vise to press the old bearings out and a set of large sockets (you use them as "pressing pistons"). Steve Falco
ins_aeas@jhunix.UUCP (Earle A .Sugar) (12/03/85)
> > The automatic transmission of my '77 Plymouth Volare is producing a > heavy thump when shifted from Neutral to either Reverse or Drive. > The harshness of the transmission engagement is roughly proportional to > the idling speed. The thump can jolt the car at cold idle speed (1400 rpm), > but is tolerable at hot idle (700 rpm). The level and quality of the > transmission fluid has been checked out fine, the idle speeds are > also alright. Other than the stated problem the trasmission works fine > (no delay, no slippage). I would appreciate any pointer > to the probable cause of the problem. Thanks. > > > Kaihu Chen > {ihnp4,vonvex,pur-ee}!uiucdcs!chen The problem may be elsewhere in the driveline. Worn U-joints on your driveshaft, a worn differential, etc. may cause a clunk when the transmission is engaged from neutral or park into drive or reverse. -- ______________________________________________________________________________ Earle A. Sugar Disclaimer:"I doubt anyone else here agrees with me." USENET: ...!seismo!umcp-cs!aplvax!aplcen!jhunix!ins_aeas CSNET:ins_aeas@jhunix.csnet ARPA:ins_aeas%jhunix.csnet@csnet-relay.arpa BITNET: INS_BEAS@JHUVMS (as a last resort) or call 301-889-0815 after 6 P.M. EST
sat@tifsie (12/04/85)
> /* ---------- "harsh transmission engagement" ---------- */ > The automatic transmission of my '77 Plymouth Volare is producing a > heavy thump when shifted from Neutral to either Reverse or Drive. > The harshness of the transmission engagement is roughly proportional to > the idling speed. The thump can jolt the car at cold idle speed (1400 rpm), > but is tolerable at hot idle (700 rpm). The level and quality of the > transmission fluid has been checked out fine, the idle speeds are > also alright. Other than the stated problem the trasmission works fine > (no delay, no slippage). I would appreciate any pointer > to the probable cause of the problem. Thanks. > Check your universal joints, if they're loose (loose bearings) they could cause the `thump' you describe. The thump would be proportional to the engine speed. An easy way to check it out is to reach under the car and twist the crank shaft (make sure the car is not running and that it is in Park). If there is play (slop) at either the front or rear U-joint, I would suggest that both joints be replaced at the same time. If it's not the universal joints, you might want to also check the motor mounts (loose or broken), however, this is more of a wild guess. Good Luck. Scott @ {convex!smu, rice, texsun}!tilde!tifsie!sat
billj@rocksvax.UUCP (Bill Jeffers) (12/05/85)
In article <1336@jhunix.UUCP> ins_aeas@jhunix.UUCP (Earle A .Sugar) writes: >> >> The automatic transmission of my '77 Plymouth Volare is producing a >> heavy thump when shifted from Neutral to either Reverse or Drive. >> The harshness of the transmission engagement is roughly proportional to >> the idling speed. The thump can jolt the car at cold idle speed (1400 rpm), >> but is tolerable at hot idle (700 rpm). The level and quality of the >> transmission fluid has been checked out fine, the idle speeds are >> also alright. Other than the stated problem the trasmission works fine >> (no delay, no slippage). I would appreciate any pointer >> to the probable cause of the problem. Thanks. >> Kaihu Chen >> {ihnp4,vonvex,pur-ee}!uiucdcs!chen >The problem may be elsewhere in the driveline. Worn U-joints on your driveshaft, >a worn differential, etc. may cause a clunk when the transmission is engaged >from neutral or park into drive or reverse. > >Earle A. Sugar This may also be normal. Automatic transmissions can object to being put in gear at 1400 rpm (a little high). The cold idle speed can be adjusted but stalling problems may result. If it was my car I would adjust the cold idle down to about 1000 and try it. If stalling occurs tweak it back up. Anyone know what the service manual says the cold idle speed should be. the slower the idle speed the smoother the engagement. Billj
ugzannin@sunybcs.UUCP (Adrian Zannin) (12/07/85)
> > The automatic transmission of my '77 Plymouth Volare is producing a > heavy thump when shifted from Neutral to either Reverse or Drive. > The harshness of the transmission engagement is roughly proportional to > the idling speed. The thump can jolt the car at cold idle speed (1400 rpm), > but is tolerable at hot idle (700 rpm). The level and quality of the > transmission fluid has been checked out fine, the idle speeds are > also alright. Other than the stated problem the trasmission works fine > (no delay, no slippage). I would appreciate any pointer > to the probable cause of the problem. Thanks. One thing you might want to consider is to check the universal joints on the driveshaft itself. If you at times hear a metallic like "klink" when the transmission engages, then it probably is your universal joints. To roughly describe what is happening, imagine two of those trick rings that a magician uses. Imagine them interlooped, with the plane of one ring perpendicular to the other. Now hold one ring steady with one hand and give the other ring a sharp 90-degree twist. Notice how it contacts with the other ring? This is what happens when your universal joints are worn. I would suggest having it checked out as soon as possible, because even though you may not notice it while you are driving, the same thing is constantly happening as you drive, and accelerate, decelerate, stop, start, etc. Eventually you will actually break the universal joint and/or drive shaft, and if it is really bad, you could even drop the driveshaft itself (it happened to me!). Good luck and let me know how yo made out... -- Adrian Zannin ..{bbncca,decvax,dual,rocksvax,watmath,sbcs}!sunybcs!ugzannin CSNET: ugzannin@Buffalo.CSNET ARPANET: ugzannin%Buffalo@csnet-relay.ARPA BITNET: ugzannin@sunybcs.BITNET
rjs@hpfcla.UUCP (12/14/85)
Despite the fact that everyone here is mentioning U-joints, I suspect that you are experiencing some play in the rear-end. Chrysler products are notorious for this as well as other read-end noise as they get older. If you can reduce you idle some it will help. If you want to spend the bucks you could have the rear-end rebuilt but this is typically expensive. My best suggestion is that you just live with it. As noisy as I have ever heard any chrysler rear-end I have have never seen one fail. I had a 1974 Dodge Monaco with the posi rear-end (this was the first year they went from the plates to cones in the posi rear-ends) that would vibrate the hell out of the car under 15 mph. However, the car still went for over 100,000 miles and died for lots of other reasons NOT including the rear-end. Bob Schneider ihnp4!hpfcla!hpfcll!rjs
chen@uiucdcsb.CS.UIUC.EDU (12/25/85)
I received many responses regrading the harsh (automatic) transmission engagement problem I posted sometime ago. Most responses I received suggest worn-out u-joints, but the u-joints were replaced to no avail. Upon careful examination of the drive train, I found out that most people were at least partially right - the problem is indeed caused by excessive play in the drive train. However, in my case the source of play seems to come from BEFORE the transmission output shaft (not BETWEEN the transmission output shaft and the drive shaft). I was able to turn the drive shaft clockwise/counterclockwise almost a full half inch before hearing a slight click. There is also slight, probably ignorable, play in the differential as another response has predicted. As the problem has turned out to be much more expensive than I am willing to pay for an old car, I am most likely going to leave it alone. Thanks again for all of you who suggest a fix. Kaihu Chen chen@uiuc.arpa Department of Computer Science University of Illinois at Urbana-Champaign