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Question for OD Experts - OD Dropping Out When - Updated Sep-10

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Donthuis Avatar
Donthuis Don van Riet
Rijswijk, ZH, Netherlands   NLD
Well just when I was typing to Dick... smileys with beer
Thanks to you as well, Clay. Recipe is simple then, which is just as well not possessing the Bentley manual. I do own the first Dutch BL manual in foto copy (still with just the old OD in), an early thicker Haynes stopping in 1973, a thinner later one covering up to 1980 and Lindsay Porters book on the MGB. Last but not least Astley's book on electrics, which is only partly relevant here....

BTW this 400+ psi value at just 30mph/50kmh is a daunting one, at such low speed my OD used to come in rather late...eye rolling smiley

In reply to # 3598964 by ClayJ Morning Don,
The factory copy Bentley manual includes the testing procedure using a diagnostic pressure gauge. Charlie obtained his gauge from an on-line resource for roughly $50. To use, you remove the relief valve plug and screw the gauge in that location, this would be the same for both black and blue label ODs. With the car secured on jack stands, select fourth gear, OD on, the expected reading at 30mph is 400-420 psi (I've assumed these test pressures are cold).

Phil, the unit looks like the one pictured below.

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ClayJ Avatar
ClayJ Silver Member Clay Johnston
Mt. Olive, MS, USA   USA
1972 MG MGB
Don,
In testing the OD with a drill, if all is working properly the OD will reach the 400-420psi quite easily, I was surprised the first time Charlie and I tested one.

ClayJ Avatar
ClayJ Silver Member Clay Johnston
Mt. Olive, MS, USA   USA
1972 MG MGB
Good evening all,
Thought I would provide resolution information on my overdrive low pressure dropout issue for future reference.

Previous activities documented on this thread included: changed 20W50 and filter, replaced pump o-rings, relief valve o-rings, solenoid o-rings, reseated solenoid valve ball, replaced 20W50 with ND-W30 oil. The relief valve had no shims.

At the end of these activities my 30mph pressure was 335psi, Bentley manual states I should see 400-420psi. I installed two 0.016" thick shims ordered from McMaster-Carr at the top end of relief valve spring (between the high-pressure relief valve spring and the low-pressure valve body). After installation, my pressure is just over 410psi at 30mph. That is 75psi gain on a total of 0.032" of shims or 2.3psi per 0.001", a 0.016" thick shim would yield 37psi gain, a 0.005" shim would gain just under 12psi.

Here are the shims I ordered from McMaster-Carr:
91017A475 316 Stainless Steel Shims for Lengthening 1/2" Diameter Screw Shoulder, 0.005" Thick, Packs of 10
https://www.mcmaster.com/#catalog/123/3287/=19m5hwv

91017A575 316 Stainless Steel Shims for Lengthening 1/2" Diameter Screw Shoulder, 0.016" Thick, Packs of 10
https://www.mcmaster.com/#catalog/123/3287/=19m5iou

I was working on a club member's OD this afternoon, his pressure was 320psi, I installed two 0.016" shim and a 0.005" shim to bring his pressure just over 400psi at 30mph.

That's all I know. Many Thanks to everyone that posted to the thread and PM'd me with suggestions.
-----------------------------------------------------
overdrive, over drive, over-drive, od, o-d, shim, shims

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ohlord Avatar
ohlord Gold Member Rob C
North of Seattle, N.W., USA   USA
1957 Land Rover Series I "EYEYIYI"
1971 MG MGB
1971 MG MGB "Bedouin 2"
thumbs up shims aren't psi. linear
Your combination worked for youthumbs up
Thanks for the updatesmileys with beer



"I'm a long way gone down this wild road I'm on
It's gonna take me where I'm bound
It's a long way around"



"These are the days that must happen to you"

RD2 Radar/ Electronic Warfare Technician
Vietnam 1969-1972



Edited 1 time(s). Last edit at 2017-10-01 02:41 AM by ohlord.

geezer Avatar
geezer Silver Member charles durning
Magee, Mississippi, USA   USA
1958 MG Magnette ZB "Chick Magnette (sold)"
1967 Morris Minor 1000 Saloon (2-door) "Marvin"
1974 MG MGB GT
Success!!!



Who's version of right are we talking about? When you get 10 LBC owners in a room you'll get 12 different answers.

Donthuis Avatar
Donthuis Don van Riet
Rijswijk, ZH, Netherlands   NLD
It shows the advantage of having the special pressure gauge we discussed earlier in the garage. Strange that this shimming is not mentioned anywhere on this complete disassembly and assembly recipe we also got. Renewing the O rings in the different elements and checking on a pump spring length are the only actions mentioned. eye rolling smiley

I wonder what happens if one just orders new springs in addtion to the O rings and compare their length with the ones removed. Maybe with new, slightly longer springs the shimming would not be necessary? In any case, these extra parts will not cost much.

Back home from vacation I will check the MOSS catalogue for these parts and order accordingly. Cleaning out the oil passages in the OD as JT advises, will tell me whether and where sealant may have lodged itself in these parts. If nothing is found I will also order the pressure gauge for some further testing. Thanx a lot for starting this thread and the intel it contains thumbs up

dickmoritz Avatar
dickmoritz Gold Member Dick Moritz
Philly 'burbs, PA, USA   USA
Congrats on your success, Clay... thumbs up

Just for future reference, shims are most commonly fitted at the bottom of the pressure valve spring, on the relief valve plunger. This securely locates the shims concentrically in the bore. No functional difference, but it is a bit more secure than fitting them about the low pressure valve plunger, and also makes it easier to access during the tuning process...

Dick

In reply to # 3601695 by ClayJ Good evening all,
Thought I would provide resolution information on my overdrive low pressure dropout issue for future reference.

Previous activities documented on this thread included: changed 20W50 and filter, replaced pump o-rings, relief valve o-rings, solenoid o-rings, reseated solenoid valve ball, replaced 20W50 with ND-W30 oil. The relief valve had no shims.

At the end of these activities my 30mph pressure was 335psi, Bentley manual states I should see 400-420psi. I installed two 0.016" thick shims ordered from McMaster-Carr at the top end of relief valve spring (between the high-pressure relief valve spring and the low-pressure valve body). After installation, my pressure is just over 410psi at 30mph. That is 75psi gain on a total of 0.032" of shims or 2.3psi per 0.001", a 0.016" thick shim would yield 37psi gain, a 0.005" shim would gain just under 12psi.

Here are the shims I ordered from McMaster-Carr:
91017A475 316 Stainless Steel Shims for Lengthening 1/2" Diameter Screw Shoulder, 0.005" Thick, Packs of 10
https://www.mcmaster.com/#catalog/123/3287/=19m5hwv

91017A575 316 Stainless Steel Shims for Lengthening 1/2" Diameter Screw Shoulder, 0.016" Thick, Packs of 10
https://www.mcmaster.com/#catalog/123/3287/=19m5iou

I was working on a club member's OD this afternoon, his pressure was 320psi, I installed two 0.016" shim and a 0.005" shim to bring his pressure just over 400psi at 30mph.

That's all I know. Many Thanks to everyone that posted to the thread and PM'd me with suggestions.
-----------------------------------------------------
overdrive, over drive, over-drive, od, o-d, shim, shims



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

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Attachments:
MGB overdrive pressure valve cutaway.jpg    21 KB
MGB overdrive pressure valve cutaway.jpg

ClayJ Avatar
ClayJ Silver Member Clay Johnston
Mt. Olive, MS, USA   USA
1972 MG MGB
Thanks Rob, I'm sure you're correct that the result of shimming is not linear.

Dick I appreciate the note on the correct location for the shims.

Donthuis Avatar
Donthuis Don van Riet
Rijswijk, ZH, Netherlands   NLD
Fine overview, I wonder whether similar overviews are available for solenoid and pump assemblies. My MOSS picture (in exploded view) contains all parts, but is not so clear eye rolling smiley

In reply to # 3601880 by dickmoritz Congrats on your success, Clay... thumbs up

Just for future reference, shims are most commonly fitted at the bottom of the pressure valve spring, on the relief valve plunger. This securely locates the shims concentrically in the bore. No functional difference, but it is a bit more secure than fitting them about the low pressure valve plunger, and also makes it easier to access during the tuning process...

Dick

In reply to # 3601695 by ClayJ Good evening all,
Thought I would provide resolution information on my overdrive low pressure dropout issue for future reference.

Previous activities documented on this thread included: changed 20W50 and filter, replaced pump o-rings, relief valve o-rings, solenoid o-rings, reseated solenoid valve ball, replaced 20W50 with ND-W30 oil. The relief valve had no shims.

At the end of these activities my 30mph pressure was 335psi, Bentley manual states I should see 400-420psi. I installed two 0.016" thick shims ordered from McMaster-Carr at the top end of relief valve spring (between the high-pressure relief valve spring and the low-pressure valve body). After installation, my pressure is just over 410psi at 30mph. That is 75psi gain on a total of 0.032" of shims or 2.3psi per 0.001", a 0.016" thick shim would yield 37psi gain, a 0.005" shim would gain just under 12psi.

Here are the shims I ordered from McMaster-Carr:
91017A475 316 Stainless Steel Shims for Lengthening 1/2" Diameter Screw Shoulder, 0.005" Thick, Packs of 10
https://www.mcmaster.com/#catalog/123/3287/=19m5hwv

91017A575 316 Stainless Steel Shims for Lengthening 1/2" Diameter Screw Shoulder, 0.016" Thick, Packs of 10
https://www.mcmaster.com/#catalog/123/3287/=19m5iou

I was working on a club member's OD this afternoon, his pressure was 320psi, I installed two 0.016" shim and a 0.005" shim to bring his pressure just over 400psi at 30mph.

That's all I know. Many Thanks to everyone that posted to the thread and PM'd me with suggestions.
-----------------------------------------------------
overdrive, over drive, over-drive, od, o-d, shim, shims

. Hide banner ads & support this website by becoming a > Gold Supporting Member <
Donthuis Avatar
Donthuis Don van Riet
Rijswijk, ZH, Netherlands   NLD
Today I finalised my own OD cleaning and O ring renewal actions, re-inserting the oil postponed to tomorrow to let the Permatex Ultra Blue on one side of the filtergasket only (the sump one) settle for 24 hrs as indicated. The OD side I just put grease on, so I can remove the sump easily in case of remaining problems.

If my OD returns to function just as i did a few weeks ago I will let the shim discussion pass me by, if not I will order the pressure gauge from the States for investigating any possible shim requirement. Just to be sure I looked at the site you indicated for the exact dimensions of these SS 3/8" shims and also looked at worldwide delivery options via eBay or Amazon. e Bay only got me metric ones, with the 0,352", close to 9 mm internal diametre missing from all suppliers, everybody jumps from 8 to 10 mm variants. Only Amazon got me a real 3/8"version, albeit with small differences, see https://www.amazon.com/dp/B004K1FF5A/ref=biss_dp_t_asn for the 0,005" thickness ones. Since my existing single shim is about 0,10 mm thick when measured, these ones equal the existing one

Thanx once more for your overview, tomorrow will tell me whether I will need all theadditional info or not smileys with beer

PS I found replacing the pump plunger with the flat side pointing to the rear the most tricky part of the whole exercise, I needed multiple tries to succeed (JT callled the piece "a real bugger"winking smiley

In reply to # 3601695 by ClayJ Good evening all,
Thought I would provide resolution information on my overdrive low pressure dropout issue for future reference.

Previous activities documented on this thread included: changed 20W50 and filter, replaced pump o-rings, relief valve o-rings, solenoid o-rings, reseated solenoid valve ball, replaced 20W50 with ND-W30 oil. The relief valve had no shims.

At the end of these activities my 30mph pressure was 335psi, Bentley manual states I should see 400-420psi. I installed two 0.016" thick shims ordered from McMaster-Carr at the top end of relief valve spring (between the high-pressure relief valve spring and the low-pressure valve body). After installation, my pressure is just over 410psi at 30mph. That is 75psi gain on a total of 0.032" of shims or 2.3psi per 0.001", a 0.016" thick shim would yield 37psi gain, a 0.005" shim would gain just under 12psi.

Here are the shims I ordered from McMaster-Carr:
91017A475 316 Stainless Steel Shims for Lengthening 1/2" Diameter Screw Shoulder, 0.005" Thick, Packs of 10
https://www.mcmaster.com/#catalog/123/3287/=19m5hwv

91017A575 316 Stainless Steel Shims for Lengthening 1/2" Diameter Screw Shoulder, 0.016" Thick, Packs of 10
https://www.mcmaster.com/#catalog/123/3287/=19m5iou

I was working on a club member's OD this afternoon, his pressure was 320psi, I installed two 0.016" shim and a 0.005" shim to bring his pressure just over 400psi at 30mph.

That's all I know. Many Thanks to everyone that posted to the thread and PM'd me with suggestions.
-----------------------------------------------------
overdrive, over drive, over-drive, od, o-d, shim, shims



Edited 1 time(s). Last edit at 2017-10-12 05:35 AM by Donthuis.

ClayJ Avatar
ClayJ Silver Member Clay Johnston
Mt. Olive, MS, USA   USA
1972 MG MGB
Hi Don,
Of note on refitting the pump. After installing the pump in the proper orientation, before installing the filter/plate, spin the driveshaft by hand to ensure the pump is straight, doesn't hang and is moving up/down smoothly.

Donthuis Avatar
Donthuis Don van Riet
Rijswijk, ZH, Netherlands   NLD
Yes Clay, that is indeed what I did, while shining with a torch upwards I looked at the coil windings and wheel move up and down (the plunger itself is hidden from sight). Still you can not get the bottom part far enough inside if the position of the plunger is not exactly right. The turning of this bottom part tends to take the plunger assembly with it, moving it the wrong way and blocking the lot. confused smiley

In reply to # 3608677 by ClayJ Hi Don,
Of note on refitting the pump. After installing the pump in the proper orientation, before installing the filter/plate, spin the driveshaft by hand to ensure the pump is straight, doesn't hang and is moving up/down smoothly.

Donthuis Avatar
Donthuis Don van Riet
Rijswijk, ZH, Netherlands   NLD
Friday the 13th has no negative influence on my OD-activities: apparently I belong to the 98% of the cases where renewal of the O rings and a thorough cleaning fully restores the OD function smiling bouncing smiley

Today I only tried with a cold gearbox and low speeds up to 40mph/64kmh; OD comes in well below 30mph/50kmh and switches off as well. Since ever warm weather is forecast for the coming days a longer drive with the B open is planned for this weekend. For the time being I see no need for extra shims. I bought a thinner fibre washer for the bottom part: instead of 1,58 mm thick this one measures only 1,06mm. IF the O ring higher up gives way for just this 0,52mm (about 0,02 " or the thickness equals 4 shims of 0,005" in total), overall pressure on the valve may rise with about 50psi is my guess.

But once again, for now I see no need. eye rolling smiley

PS Back to the oil leakage problem, I found one on my MANN W 916/1 oil filter yesterday and tightened it today slightly with a tool (normally tightening by hand is tight enough)



Edited 4 time(s). Last edit at 2017-10-13 10:56 AM by Donthuis.

Donthuis Avatar
Donthuis Don van Riet
Rijswijk, ZH, Netherlands   NLD
Thread can be closed: a trial trip of about 100 miles in the beautiful Dutch landscape found me today with a perfectly working OD, whether in 3d or 4th and as off lower speeds as well. Temperature of the gear oil in 23+C ! ambient made no difference either, smooth action was retained after heating up in this many hours of driving both on highways and country roads cool smiley thumbs up

ohlord Avatar
ohlord Gold Member Rob C
North of Seattle, N.W., USA   USA
1957 Land Rover Series I "EYEYIYI"
1971 MG MGB
1971 MG MGB "Bedouin 2"
Sounds great.


Wish I was driving the old land rover across your wonderful countryside. smileys with beer



"I'm a long way gone down this wild road I'm on
It's gonna take me where I'm bound
It's a long way around"



"These are the days that must happen to you"

RD2 Radar/ Electronic Warfare Technician
Vietnam 1969-1972


Attachments:
Awesome_1477739449038.jpg    38.6 KB
Awesome_1477739449038.jpg

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