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Overdrive engaging with time delay

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BN6_2197

BN6_2197

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Gents,

does anybody have also the effect that the overdrive engages with a time delay of approximatley 5 secomds? Typically I engage the overdrive in 4th gear at 2000rpm. The overdrive does not engage at the same time I put the switch but with a delay of 5 seconds. Any ideas what‘s the problem or is it an expected behaviour?

Regards,

Volker
 
Yes, check the oil level first (the dipstick is on the gearbox, they both usually leak). You can try a 'thicker' oil--there's lots of threads on here about which oil to use--but that could conceivably make it worse. The OD has an accumulator--a spring-loaded piston--that should build the oil pressure starting from the time the car is placed in gear so the actuating pressure is available immediately (I think they work in reverse). The accumulator should hold at least 400psi or so, but I think the OD will work, albeit more slowly, if the pressure is a little less than that. The other possibilities are the pump which, if not in good nick would not build sufficient pressure, and the two actuating pistons which separate the cone clutch and lock the sun gear. If either of these has worn rings* or a scored cylinder pressure could be lower. I've not heard of this happening--they usually go intermittent or fail outright--but if the solenoid was slow in activating that could at least contribute to the delay.

* I don't recall which Healey you have, but earlier cars' ODs have actuating pistons with metal rings which can wear the bore, later cars have pistons with O-rings. All Healeys AFAIK came with accumulators with metal rings (3), but at least one vendor has one with an O-ring and DWR sells an 'uprated' accumulator which actuates a bit quicker--1-2 seconds--but has a somewhat more abrupt engagement.
 
2000 is a bit low to engage the over drive. It will probably "lug" the engine (not good). (Okay guys attack me but 3500+ rpm makes more sense to me. I think each of us has their own sweet spot.)
 
Nobody has mentioned the filter screen that needs to be cleaned in the OD ?
 
Five seconds is a bit long but did this get longer over time or suddenly change? Is everything else normal? As above, do the easy stuff first. Obviously check the oil level. If low, service and test. I've used 30wt non-detergent as the book recommends for years with no issues. Be sure you service with what is in there. If you don't know, I'd drain it and flush it a bit and service with the oil of your choice.

If the oil is discolored ( dark) but there is no significant metal in the sump screen, dark oil in the gearbox may be caused by deteriorating O rings and that could be your issue. The oil should remain pretty clean if changed every few years.

When you are in the garage, not running and you turn on the ignition, flip the od switch on and make sure that as you push the shift lever towards 3rd and 4th gear that you hear the click of the solenoid. I can't think of why there would be a delay but it ian easy check. If the click is immediate you know there is not an electrical issue. The valve piston is moved by shafts and levers so if it is rigged correctly it should move quickly but if it were binding ( dirty) enough it might take the solenoid force a little more time to compress the spring and move the ball bearing off the seat to engage the OD. It is possible that the operating valve is hanging up a bit and if you are familiar with how it works it is pretty easy to pop the cap off it and pull out the spring, ball bearing and then the valve piston and it should slide up and down in the housing fairly easily with no binding. That's all I have without more info.
 
Gents,

I thought of an oil issue as well. Hence I changed the oil (last change before ablut 7 years with 1000 miles per year driving). It was dark but no metal found. Also the oil filter of the O/D was clean.

After doing and checking all this, the problem still exists.

Volker
 
I think--I've never run an experiment--that engaging at a slower speed might cause some delay. However, the pump that builds the high pressure has a check valve on it so once pressure is built it shouldn't drop off. If the electricals check out, the problem is either a) the pump isn't building sufficient pressure or b) the accumulator is worn enough that it lets the pressure bleed off (I've not seen is described anywhere, but there is a hole in the accumulator sleeve that appears to function as pressure relief once the heavy spring has been compressed sufficiently) or c) a combination of these two. This doesn't rule out the actuating pistons which could have worn their cylinders--for cars up to BN/T7 OD# 22/3009/607--or the O-rings on later cars (I suspect if these are worn enough to cause slow engagement the accumulator is worn as well). The pump can wear, but as it has no rings this is somewhat less likely if good, clean oil has been used throughout its life (I rebuilt my BJ8's OD at 205K miles and the pump was fine).
 
I would be curious to know if the time delay is consistently around 5 seconds? I had a related issue, where the time delay was longer when the car was cold and would lessen after the car warmed up. Over time the delay got worse until the OD would not engage at all, no matter how warmed up the car was. The problem turned out to be a very worn OD transmission switch. I'm guessing that once the car was warm the transmission components would expand enough for the switch to work, but eventually the switch wore out to the point where no amount of warming up would enable it to work. Replacing the switch was an easy fix.
 
I recall that my pre-rebuild time delay was way too long for my taste. With the uprated accumulator, it shifts within a second, about like a regular shift.
 
Had a similar issue with my overdrive: it turned out that the rubber dustcover on the solenoid folded up and restricting the free movement of the solenoid rod. After removing the dustcover the overdrive worked OK.
 
nevets said:
I would be curious to know if the time delay is consistently around 5 seconds? I had a related issue, where the time delay was longer when the car was cold and would lessen after the car warmed up. Over time the delay got worse until the OD would not engage at all, no matter how warmed up the car was. The problem turned out to be a very worn OD transmission switch. I'm guessing that once the car was warm the transmission components would expand enough for the switch to work, but eventually the switch wore out to the point where no amount of warming up would enable it to work. Replacing the switch was an easy fix.
Click to expand...

In my (limited) experience, the opposite was more common; when the OD got warm, it would engage a bit slower. Most likely this was due to the gearbox/OD oil thinning out (which could indicate a worn accumulator or actuating pistons). Electricals getting temperamental when hot is not uncommon. I had an OD switch that would cause the OD to disengage at random times. I was on the road in Canada and didn't have a spare--I do now--and pulled it in a hotel parking lot, opened it up and filed the points and it got us home.
 
Bob, thanks for the feedback. The OD switch plunger was very worn, in fact it had a major flat spot, which is why I hypothesized that once the metal parts warmed up they would expand enough for the plunger to interact with the corresponding component(s). Just a theory.
 
johnea said:
Had a similar issue with my overdrive: it turned out that the rubber dustcover on the solenoid folded up and restricting the free movement of the solenoid rod. After removing the dustcover the overdrive worked OK.
Click to expand...

Before I rebuilt my OD my solenoid dust cover was shot, and I used a couple turns of this:

https://www.amazon.com/X-Treme-Tape-TPE-XZLB-Silicone-Triangular/dp/B01J51XYTI

Held up well for a couple years until the rebuild, when I replaced the solenoid on GPs.
 
I'm going to join this thread because I have had the same problem arise in the last few months with my phase II BJ8. Last year, I had the engine rebuilt and since then the overdrive has lagged at least 5 seconds - perhaps even more. Then more recently, it would drop out of OD if I decelerated. The Bentley manual describes the latter as likely due to the throttle switch, but I've gone through that and it seems to working fine. Also, I can hear the solenoid fire right away so the delay is likely in the hydraulics. Now, it no longer engages. The oil in the tranny is new and topped up. So, I think I'm looking at rebuild. Can you service the OD pump without removing it from the car? If you have to remove the OD, does this require pulling the transmission as well? Every description of an OD rebuild seems to assume that the transmission has been pulled. It would seem like you could just disconnect the adapter plate from the transmission.

Bruce Tomblin
 
I suggest you poke around on the internet and you will find videos of several people removing and installing the OD module from the transmission. If you do, you will see it is not a situation where it will slip back on. I suspect it would not be worth the trouble to see if it is even possible without the gearbox out of the car. Normally the OD is installed with the transmission in a vertical position. It also involves turning the shafting to facilitate putting them together. The oil pump, except for the cam on the shaft that drives it can be pulled from below with a special tool. Of course they do eventually wear out but it is not very common that that is the problem.

Rather than go into more detail, I suggest you read the threads on this forum that detail what the problems have been for many of the contributors including me. Perhaps the best video series is on youtube hare is the link for the installation of the od.
https://youtu.be/cgNadKy16QE
 
The OD can be removed and leave the transmission in the car . Unbolt the rear end of the transmission from the frame . Jack up the rear of the transmission from below (watch your rad fan doesn’t hit your rad ) go as high as you can without bending anything or damaging the rad .
Obviously you need remove the drive shaft .
unbolt the OD and pull it off .
Getting it back on is a real treat , trying to line up the double spline and keep the pump plunger pulled down is an art in itself but can be done with patience .
DONT FORCE IT BACK ON YOU WILL BREAK SOMETHING INTERNALLY IN THE OD .
Celebrate with a few cold ones once it’s back in .
 
The key to getting the spring loaded oil pump plunger onto the cam without goobering it up is to compress it and run some stainless safety wire to keep it retracted and when the parts are mated, pull out the wire. This would not be a one person job if in the car. Also, if you remove the oil pump plunger be aware that the fork end is assymetrical and this end that holds the roller must be installed correctly as it can be done 180 degrees off and that will bend the plunger shaft. I know because the PO of my car did that and that is one reason the OD was inop when I tore jnto it. The pump piston was jammed due to getting bent.

I have posted about it before but one reason for low oil pressure in the OD is a relatively simple fix if it is the problem. It was for me. I still had low oil pressure after I had replaced all the seals in the unit. What it turned out to be was some pretty serious pitting on the seat for the ball bearing pressure relief check valve in the OD oil pump casting. On the side shift transmissions it is accessable while in the car. I was able to dress the seat with a fresh ball bearing of the proper size glued to a stick and chucked in a drill with lot of valve grinding compound. Lots of coarse and then fine to make a new seat for a fresh ball bearing. The old ball bearing was also nowhere near round anymore. Bam, that did the trick and full oil pressure was restored. The pressure relief valve simply wasnt ever closing so pressure built slowly early on and got to the point where the OD would not actuate. That was why the previous owner had taken it apart, not knowing he'd created a new problem by putting the pump back together incorrectly. Yikes, the things we go through......
 
I purchased a pressure gauge from James R. Holekamp and tested the pressure at the operating valve. As expected it was about 120 lbs so this is likely the problem. Following Jon's suggestion I purchased a new ball for the operating valve and used the old one to dress the seat to see if I could get the same resolution to the pressure problem. I super glued the old ball to some tubing and used this along with valve grinding compound. I'm not sure how much grinding is needed, but after a bit of grinding I stopped to check to see if I was making progress. Instead of better pressure, I lost what I had. The problem is that I don't seem to be able to fully clean the grit from the the assembly. The operating valve (spindle) seems to bind - probably due to the grit. I've tried using WD-40 as a wash and also cotton swabs but I can still fee some residual grit and I no long have any pressure. Any thoughts?

I've concluded that having a Healey during covid is a good thing. It always gives me something to do while socially distanced. It seems as though when I get one thing fixed another pops up.
 
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