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Overdrive Stopped - Need help w/ trouble shooting...

Posted by AHark

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Overdrive Stopped - Need help w/ trouble shooting... #1
AHark Andy Harkness Pittsburgh, USA 1975 MG MGB 1978 MG MGB V6 Conversion	Posted: May 06, 2012 09:18AM Registered: 4 years ago Posts: 865

I installed a working OD last year. Was working fine as I test drove it in the car it was pulled from and following intstallation in my car it worked smoothly. Was working fine until it gently cut out a couple weeks ago. I check the electric circuit, powers on and off with OD switch and gear selection as it should. Check oil level, it was where it should be too - I replaced front and real seals before installing and it didn't leak at all. So it's either I drain and proceed with the cleaning process as presented by John Twist or add AT fluid to clean it out. Guess it could be the solinoid too. Any recommendations for an appropriate next step? Thanks

Found a past post that says resistance in the solinoid should be 17 ohms, sound right?

Edited 1 time(s). Last edit at 05/06/2012 09:30AM by AHark.

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Re: Overdrive Stopped - Need help w/ trouble shooting... #2
chris Chris Roop Pendleton, OR, USA	Posted: May 06, 2012 10:34AM Registered: 14 years ago Posts: 30,247

Check the solenoid, clean the strainer. I wouldn't add ATF.That is more because of superstition than knowledge though.

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Re: Overdrive Stopped - Need help w/ trouble shooting... #3
dickmoritz Dick Moritz Philly 'burbs, PA, USA	Posted: May 06, 2012 10:49AM Registered: 3 years ago Posts: 7,264

Andy,

Suggest you check power at the solenoid in the prescribed gear(s). If you have power there at the right time, have your lovely wife/girlfriend/boyfriend cycle the o/d switch to see if you can hear and feel the solenoid click.

If it clicks, you should probably do the John Twist service.

If it doesn't click, dig out your arm with two wrists in it and try to check for power on and off at the overdrive isolation switch. It's the same as the backup light switch, except the backup light switch is the one you can reach... grinning smiley

If power in but no power out of the overdrive isolation switch, time for a switchectomy... eye popping smiley

If no power to the switch, trace wiring and repair as needed.

Good luck, and do keep us posted on your progress.

Dick

Errabundi Saepe, Semper Certi
(Often wrong, but always certain)

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Re: Overdrive Stopped - Need help w/ trouble shooting... #4
AHark Andy Harkness Pittsburgh, USA 1975 MG MGB 1978 MG MGB V6 Conversion	Posted: May 06, 2012 11:23AM Registered: 4 years ago Posts: 865

Dick, I have power at the solinoid in appropriate gear, 3 and 4 only as it should be.

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Re: Overdrive Stopped - Need help w/ trouble shooting... #5
mrkenmgb Ken DeLEEUW Ormond Beach , fl, USA 1970 MG MGB GT "Old Ormond White" 1976 MG MGB V6 Conversion "Boynton Blue"	Posted: May 06, 2012 11:25AM Registered: 7 years ago Posts: 1,120

Andy
I had a very interesting happen to me when I had an overdrive. It wouldn't work unless I put pressure and held back on the gear shifter. My problem was the switch was loose on tranny. It was a blue label. A real pain to tighten it while in the car. But once done never a problem after. Just might be something to check on.
Ken

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Re: Overdrive Stopped - Need help w/ trouble shooting... #6
dickmoritz Dick Moritz Philly 'burbs, PA, USA	Posted: May 06, 2012 12:02PM Registered: 3 years ago Posts: 7,264

In reply to # 2059876 by AHark Dick, I have power at the solinoid in appropriate gear, 3 and 4 only as it should be.

Andy,

Can you hear and feel the solenoid click in and out?

Dick

Errabundi Saepe, Semper Certi
(Often wrong, but always certain)

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Re: Overdrive Stopped - Need help w/ trouble shooting... #7
gooser Drake Myers Danville Va, USA	Posted: May 06, 2012 12:30PM Registered: 5 years ago Posts: 6,929

look and see that the pump is still working as it should.

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Re: Overdrive Stopped - Need help w/ trouble shooting... #8
AHark Andy Harkness Pittsburgh, USA 1975 MG MGB 1978 MG MGB V6 Conversion	Posted: May 06, 2012 02:05PM Registered: 4 years ago Posts: 865

Pulled the solenoid and bench tested ok. Headed back out to check out the pump for movement.... Filter was dirty well about 1/2 of it, thinking that may be it. I have a new filter so if the pump is moving I'll assemble and then give it a shot.

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Re: Overdrive Stopped - Need help w/ trouble shooting... #9
chris Chris Roop Pendleton, OR, USA	Posted: May 06, 2012 04:00PM Registered: 14 years ago Posts: 30,247

Those screens can be an issue.

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Re: Overdrive Stopped - Need help w/ trouble shooting... #10
AHark Andy Harkness Pittsburgh, USA 1975 MG MGB 1978 MG MGB V6 Conversion	Posted: May 06, 2012 07:24PM Registered: 4 years ago Posts: 865

Road tested and nothing. Bummer. Not sure where to go from here. Does the OD pack unbolt from the front section? Thinking about a remanufactured OD unit, anyone go that route?

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Re: Overdrive Stopped - Need help w/ trouble shooting... #11
gooser Drake Myers Danville Va, USA	Posted: May 06, 2012 07:28PM Registered: 5 years ago Posts: 6,929

it does unbolt but not while in the car. what kind of oil are you using?

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Re: Overdrive Stopped - Need help w/ trouble shooting... #12
AHark Andy Harkness Pittsburgh, USA 1975 MG MGB 1978 MG MGB V6 Conversion	Posted: May 06, 2012 07:31PM Registered: 4 years ago Posts: 865

20/50 castoil.

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Re: Overdrive Stopped - Need help w/ trouble shooting... #13
rundjk David Kinsey Virginia Beach, USA 1980 MG MGB "Runaway"	Posted: May 06, 2012 08:50PM Registered: 3 years ago Posts: 1,476

At the end of your process, when you get it working, do the other thing John Twist strongly recommends and add an in-line fuse to the OD circuit. Saved my bacon one time when foil insulation was pushed by wind/vibration to the switch and connected the circuit!

David

David J. Kinsey
Virginia Beach
Tidewater MG Classics
1980 MGB "Runaway"

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Re: Overdrive Stopped - Need help w/ trouble shooting... #14
AHark Andy Harkness Pittsburgh, USA 1975 MG MGB 1978 MG MGB V6 Conversion	Posted: May 06, 2012 09:03PM Registered: 4 years ago Posts: 865

I added a fuse to the harness connection last year. Is there a special tool to get that plug out, you know the one with 2 holes that hard to screw out.
? I tried needle nose players with vise grips, wrenches, etc. Couldn't get it...

Found it, its called a face pin spanner wrench.... if any one wants to know.

Edited 1 time(s). Last edit at 05/06/2012 09:34PM by AHark.

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Re: Overdrive Stopped - Need help w/ trouble shooting... #15
chris Chris Roop Pendleton, OR, USA	Posted: May 06, 2012 09:38PM Registered: 14 years ago Posts: 30,247

So, where are you at right now? You had a working unit, it quit, you have juice to the solenoid, the solenoid clicks in, you have cleaned the screen, then what?

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Roop's MG – Pendleton, OR USA Check out the Vendors' Deals page for the clutch, brake, and water pump sale. Please email me at the business address for business concerns.

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Re: Overdrive Stopped - Need help w/ trouble shooting... #16
AHark Andy Harkness Pittsburgh, USA 1975 MG MGB 1978 MG MGB V6 Conversion	Posted: May 06, 2012 09:52PM Registered: 4 years ago Posts: 865

Filled the OD with fresh 20/50 oil, took it out for a drive. And no overdrive. I came full circle to where I started.... I may try to service it again, I order a spanner wrench to get open it up. Planning to drive it this way for a while. I sure do miss the OD though.

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Re: Overdrive Stopped - Need help w/ trouble shooting... #17
thomaslea1 Tom Lea Central Illinois, USA 1968 MG MGB	Posted: May 06, 2012 09:59PM Registered: 5 years ago Posts: 647

You need to also check for pressure build-up internally. If you don't have pressure you will never make it work. If I'm not mistaken it should run in the 420PSI range. Pressure is taken at the plug holding the check valve assy in place. I ordered a spare plug and drilled and tapped it for a fitting. Then snaked a length of brake tube from the plug up thru the shifter hole and attached a gauge.

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Re: Overdrive Stopped - Need help w/ trouble shooting... #18
Swamperca Swamper CA Nor Cal, USA 1969 MG MGB GT "Rat" 1969 MG MGC GT "A 69 MGC" 1970 MG MGB GT "Widow" 1971 MG MGB "Ruby" 1974 MG MGB "Groovy B"	Posted: May 06, 2012 10:17PM Registered: 8 years ago Posts: 7,659

O-Rings bad, time for a rebuild.

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Re: Overdrive Stopped - Need help w/ trouble shooting... #19
pooch2 aussie 1968 MK 1 By the Beach, south coast NSW, Australia	Posted: May 07, 2012 02:11AM Registered: 4 years ago Posts: 4,171

I agree, now is the time to take it to someone to verify over 400 PSI is available.

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Re: Overdrive Stopped - Need help w/ trouble shooting... #20
AHark Andy Harkness Pittsburgh, USA 1975 MG MGB 1978 MG MGB V6 Conversion	Posted: May 07, 2012 12:43PM Registered: 4 years ago Posts: 865

I talked to the folks at Quantum, I'm going with a reconditioned OD unit when the have on in stock. If they don't get one in over the summer I'll wait till the end of the driving season and send mine to they for rework. The OD side clutch material sounds compromised.

Edited 1 time(s). Last edit at 05/07/2012 12:50PM by AHark.

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