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BJ 8 Overdrive problems

DavidThorn

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When using the car today problem arose with overdrive in that it would engage then disengage all by itself under load. Also when it disengaged car would `free wheel` when not under load i.e. as soon as I took power off revs would drop to idle but car still moving as though clutch had been pressed !!. Quickly got worse in that by return trip o/drive would still engage but then come off even if not uder load. Have not fiddled with anything recently so it seems to have occurred by itself. Have check gearbox oil level and its correct with engine oil which has been in for about 2,000 miles. Any ideas where to start looking
 

Keoke

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HI David, First off I suggest you check the alignment of the OVD throttle switch position against the setting contained in the factory manual.---Fwiw--Keoke
 
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DavidThorn

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Thanks for prompt reply - I have connected a test lamp as described in the Haynes Manual and with the O/D switched off it goes out at about 1/5 of throttle movement
 

Keoke

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That sounds OK David. Now using your manual perform the engagement test: This is where you align the little arm on the right hand side of the OVD with a hole in the OVD case using a drill bit shank and see if that adjustment is correct.Note: While you have the key on disconnect the power to the coil it will overheat---Keoke
 

Dave Russell

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[ QUOTE ]
When using the car today problem arose with overdrive in that it would engage then disengage all by itself under load. Also when it disengaged car would `free wheel` when not under load i.e. as soon as I took power off revs would drop to idle but car still moving as though clutch had been pressed !!. Quickly got worse in that by return trip o/drive would still engage but then come off even if not uder load. Have not fiddled with anything recently so it seems to have occurred by itself. Have check gearbox oil level and its correct with engine oil which has been in for about 2,000 miles. Any ideas where to start looking

[/ QUOTE ]
There is some info on the OD solenoid adjustment here: https://www.britishcarforum.com/lore/article.php?id=073
The "book" method of setting the solenoid operating lever (alignment pin in the RH setting lever) is frequently not even in the ball park when the parts get worn a bit. Setting the ball lift is much more accurate. A pic of a ball lift setting gage that I made is attached. Anything that gives a stable & repeatable measurment will work. Note that ball lift must be measured by moving the actual solenoid plunger, not just the lever. The lift must be in the .030" to .040" range for optimum operation.

I think you may have a different problem though. The OD clutch has two positions. The sliding part is moved forward by hydraulic pressure to lock up the clutch in the OD on position. It is moved to the rear by springs, as hydraulic pressure is removed, to provide engine braking in the the direct drive position. A very likely possibility for your problem is a blocked bypass port on the OD operate valve which leaves the clutch between positions. It is easy to check. Below is a direct quote from Moss Tech. Notes:
----------------------------------
"Overdrive Faults

Fully 90% of overdrive problems that are not electrical faults are traceable to either the gear oil level being tool low, or an improper adjustment of the solenoid, so we'll skip these and concentrates on the others.

An overdrive that fails to engage can sometime be traced to dirt between the check ball and seat in the pressure regulator valve, or sometimes to a badly worn pump. Both are quite rare, though possible, so don't overlook them. Worn or broken rings on the operating pistons or the accumulator piston can make for a lazy-shifting or slipping unit.

However, the real winner is a partially or completely blocked bypass port in the operating valve. The valve, which is activated by the solenoid through the operating shaft and lever, has a small hole bored in it (about .018") which is very easily blocked by dirt, etc. The results of blockage can be really fun to find. FIrst, partial or intermittent blocking results in slow engagement, but most noticeable is that there is no compression-assisted slowdown. The unit appears to hang between overdrive and direct drive and feels like it is not in gear. Basically, what is happening is that the partially blocked valve will not allow the oil to return to the sump fast enough, and the pressure build-up above the valve tries to engage the overdrive while the unit's springs try to engage directly, and there we hang beween the two. The fun begins when the bypass port becomes COMPLETELY blocked. Above a certain speed, the pressure above the valve becomes high enough to engage overdrive, no matter what you do or where the switch is.

Fortunately, the valve blockage is easy to repair. With the transmission tunnel removed, the access to the valve is on the right side of the top of the overdrive unit and is under a 7/16" plug. Under the plug is a spring and check ball assembly which can be removed with a small magnet. After it is cleaned, it can simply be set back in place, hole-in end facing up, followed by the ball and spring assembly. It is very straightforward and easy to remedy once you find it.

Ken Gillanders
Temple City, CA"
--------------------------------------
The tiny hole is down in the side of the lower part of the valve. Increasing this hole size to .046" will increase shift speed & system reliability as the larger hole will be less likely to get plugged.
I think it is worth a check,
D
 

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DavidThorn

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Keoke and Dave Thanks it will have to wait till the weekned before I can check as you describe. The `free wheeling` concerned me I thought that may indicate a mechanical problem.
 

Dave Russell

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Attached is a drawing of the operating valve. "H" is the hole that may be plugged. The ball must seal in the aluminum lower seat "F" & also seal on the top seat of the spindle "G".

To be certain of the seating, the ball can be tapped down into the aluminum seat "F" with a soft punch. The ball can be lapped into the spindle end "G". If seating & lapping "is" done, the ball should be replaced with a new ball of the same size. Loose bearing balls can be obtained at many bearing supply shops.

As mentioned above, I have found it to be beneficial to enlarge the hole "H" to .046" diameter. A # 58 drill is .046".
D
 

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DavidThorn

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Hello from a very wet Sunday morning in Wiltshire UK. Have now performed the checks as you have said and following a test drive have to report sadly that the problem still exists.
The issues is that O/D engages but trips out within a second or 2 and when it does the car free wheels and there is no engine braking. I have a small lamp attached on the dash to show when the O/D is on and this activates as normal even when the O/D has dropped out (it extingushes when throttle is open to the normal point)
The porblem started the day after I had a bit of a `senior moment` in that whilst accelerating hard - to overtake - in O/D third gear I reached up and flicked the O/D switch off (thinking I was not in O/D and that I was engaging it) of course the engine speed went well into the red and then to make matters worse (probably) realsing what I had done I flicked it back into O/D - however it did seem to survive this at the time only over the following few days did the problem occur.
What I have done since first posting problem is - change gearbox O/D oil now refilled with SAE 40 to the specified amount -seems quite high on dipstick though!
Check operation of O/D engagement - with a drill bit into the little hole on the lever arm and casing which seems to align when O/D is engaged (although it all seems a bit sloppy) I have not made any adjustements to this.
Finally I have removed and cleaned the operating valve as suggested by Dave Russell the little hole did not appear blocked and certainly is not now - but as I have said no change. Any more suggestions ?
Just one final point as I have driving the car with the gear box tunnel cover off when the O/D has disengaged and the car is free wheeling there are some faint but strange noises comming from the area of the O/D unit.
 

vette

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David, have you always used 40w oil in the trans. In cold climates the manual suggest 30w. I have been running 30w in my BJ7 for three years. I don't know if that small change in viscosity might make a difference. The o/d seems to be very sensitive to oil pressure.
Dave C.
 
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DavidThorn

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No it was running on 20/50 when the problem occurred - I switched to 40w as I read somewhere that it may help - and it does now change to O/D more smartly - but still drops out.
 

Dave Russell

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Hi David,
It appears that the OD pump & accumulator are building & holding enough pressure to at least temporarily shift the OD actuating pistons, but then pressure is being lost or is not enough to keep the sliding clutch ring engaged.

The easiest thing to check is that the ball is not sealing to the top seat (G) of the spindle & letting the pressure bleed off through the tiny spindle hole. The ball can be lapped to the spindle top as mentioned above. Lengthen spring 0.125" to increase ball to spindle seating pressure.

Other possibilities:
The pump check ball is not sealing & allowing the pump to build full pressure. Ball under brass cap under solenoid bracket/cover. Clean & tap into it's seat. Replace it's spring or shim the existing spring 0.100", to increase seating reliability.

The operating pistons seals are leaking more than the pump can supply.
The pump is worn & can't supply enough oil flow. Both problems require major disassembly.

You can't really go much further in checking without attaching a pressure gage & monitoring pressures under actual operating conditions. Maybe time to get some expert, hands on, help. Sorry for your continuing problem,
D
 

vette

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Dave, I suspect that this is more of a hydralic problem than mechanical. If the oil pressure is not holding it in, then my next step would be to clean the strainer in the o/d. You could change the oil again to 30w and if there is any improvement, then assume it a pressure problem. In which case clean the strainer. Which should be done in any suspect situation. With a clean strainer and all external adjustments as noted, put in the viscosity oil recommended for the driving conditions, ie: weather conditions and other affects on nominal temp to the tranmission. Do all these easy things before you start tearing out the trans/od. /ubbthreads/images/graemlins/cheers.gif
ps, one more thing, you really have to eliminate the possiblity of it being the electrical control circuit. I would ensure that the electrical switches as not losing contact and dropping out the solenoid. Either jumper around all swithches, or hot wire the solenoid direct from the dash toggle switch. Don't forget there is a switch on the shifter lever that only engages in 3rd and 4th gear.
 

Keoke

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I /ubbthreads/images/graemlins/iagree.gif The best tool to access the OV's performance is a pressure gauge. For cases like yours I have experienced two electro/mechanical failures. 1] is the overdrive relay. This relay has been tapped inside. Consequently, it is possible for the tapped joint to wear through the underlying varnish intermittently causing the relay to malfunction. A second problem with this relay is the terminals become loose on the bottom causing an intermittent connection here. This latter can be resolved by re soldering the loose connections and immobilizing the terminals with a spot of super glue. However, my recommendation is to replace the relay. 2] The additional problem I have experienced is the OVD switch on the tranny extension which engages the overdrive unit is maladjusted/worn and needs to be moved closer to the anvil.--Fwiw--Keoke
 

bighly

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Perhaps it could be adjusted a bit further beyond the alignment hole. I never saw one that worked when aligned per the manual aligning the lever with the little hole using a drill bit.

Or perhaps the 2/3rd gear lockout switch needs to have a spacer removed.

Just thinking of simple non-dramatic things prior to needing to disassemble.
 
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DavidThorn

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thanks from all your help - I have looked at Dave Russells suggestions first and again removed the operating valve - I tapped the ball down and slightly streched the spring as suggested - and a definate change it is holding O/D for a few more seconds now - it still drops out - mainly under acceleration but there has been a change for the better - any I going in the right direction?
Just a further point now that I am driving it with the gearbox cover off I can watch the valve setting lever in operation. As well as watching the road ahead!! It moves when O/D is engaged but does not move when it trips out. It only returns when O/D is switched off and the throttle depressed as normal (in line with the light I have on the dash) Does this eliminate and elctrical solenoid type problems?
Finally Vette mentioned cleaning the oil strainer I did this when I changed the oil -I noticed that the gauze stainer (which was not dirty) was loose above the drain plug well it seemed to be held up against the `pump`? by a couple of thick felt washers could this be part of the problem with some pressure leaking away here also?
 

Dave Russell

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In my opinion, yes, this eliminates solenoid type problems. If you are certain that the operating valve ball is sealing on both it's upper & lower seats, tapped down onto it's seat, & lapped to the top of the spindle, spindle to ball seal is very important, ball replaced with new of the same size:

See below for operating valve adjustment.
As I mentioned in my earlier post, the pump check/non return valve may be leaking & preventing full pressure build up.

This valve is under the OD side cover & is retained by a brass plug.

Remove the operating arm & side cover by gradually & evenly releasing the cover bolts against the accumulator spring pressure. Find a 6 point socket that fits snugly on the brass plug & remove the plug, spring, & ball. The plug may be very tight. Clean the parts, tap the ball into it's seat. Replace the ball with new. (carefully measure both ball diameters for replacement. Different OD's require different ball sizes). Stretch the spring about 0.100" to increse the ball seating reliability.

Reassemble & set the operating valve (RH side) ball lift to exactly 0.040" when the solenoid is operated, & tighten the arm clamp. This is a much more reliable method of setting this critical adjustment than the book method of putting a pin through the setting gage lever. The lever setting method seldom works when the various parts get a bit of wear. If the arm is set to lift the ball too far, it won't seat on it's lower seal surface & the pump will never build full pressure. 0.040" lift is optimum, 0.060" would be maximum. Don't operate the solenoid without something in place to cover the ball. It will shoot out into oblivion otherwise.

Attached is a pic of the gage & adapter I made to measure ball lift. More crud methods of measurment may be used if necessary.
D
 

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DavidThorn

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Lots of thigs to think about and fiddle with - I have not got access to any of the gauges mentioned and bearing in mind the O/D is not working anyway would it be worth adjusting the valve setting lever a little (presumably clockwise) just to see if that helps. If I marked the original position I could always return to it
 
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