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Post by richardjones on Jul 26, 2015 22:04:00 GMT
I inherited my 1966 P5 automatic Coupe which had not been run for 12 years and have recently had the engine rebuilt by a highly capable classic car motor engineer. Various other problems have been overcome regarding fuel/carburetion and the MOT has now been completed but the engine power is not translating into road speed. A gear box specialist has tested and found sound but the problem still exists - quote from my engineer: "We have measured the propshaft speed this afternoon. Running a wheel of 57mm on the 97mm flange I was expecting an indicated speed of about 5100 rpm at an engine speed of 3000rpm in top gear, in practice this should be less due to some slip in the torque converter. The reading we got was indicated 2660rpm giving a propshaft speed of 1563rpm. If the gearbox was in 2nd it should give a propshaft speed of 2000rpm less torque converter slip which could be this difference. The other option is that the torque converter is slipping badly but the road speeds do agree with my earlier calculations for 2nd gear". Does anyone have any experience or knowledge of the likely problem or can it only be a torque converter issue?
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Post by enigmas on Jul 26, 2015 22:48:06 GMT
I presume your 1966 P5 is a Mk3 so would be fitted with a BW35 gearbox. Absolutely weird diagnostic method by your 'mechanic' with the automatic.
From what you state it seems to be slipping big time! Unless there's major damage with either the torque convertor or transmission clutches and bands, has your mechanic (since the car was recommissioned) filled the gearbox with an incorrect transmission fluid? This would cause major transmission slip with the clutches and bands.
The trans fluid used on original build factory BW35 automatics should meet Ford specification M2C-33G. So look for this specification.
Don't use Dexron ATF unless the box has been rebuilt with upgraded spec friction clutches and bands.
If you have no idea, stick with the earlier original spec trans fluids.
If the wrong ATF has been used you may be able to flush the system with the correct spec fluid.
I'm sure others will chime in here with more info regarding ATF availability in your location.
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Post by richardjones on Jul 27, 2015 9:01:19 GMT
Thank you Enigma. Yes my P5 is a mark 3 and a BW box. The transmission fluid is definitely correct and he is convinced the gearbox is not going from 2nd to 3rd gear. We have the workshop manual and the maximum revs appear to translate to maximum speed in 2nd. A re-visit to the gear box specialist is clearly needed.
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Post by enigmas on Jul 27, 2015 11:59:35 GMT
Richard take a careful look at this diagnostic chart and you'll see what is occurring. In each ratio different elements engage. Study the chart and it should be evident as to which particular element has failed. Accurate diagnosis is largely a product of elimination. If the car can be driven test it on the road in the various gears.  |
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Post by harvey on Jul 27, 2015 12:17:02 GMT
he is convinced the gearbox is not going from 2nd to 3rd gear. Does it drive in REVERSE? |
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Post by richardjones on Jul 28, 2015 21:56:56 GMT
Harvey/Enigma. Reverse gear is fine. The car is road worthy and has done c100 miles with the recently rebuilt engine but has not been put under any 'heavy' engine pressure. It would help if someone can you confirm the revs you would expect to see at a road speed of say 50 mph and 70 mph. The latest report from my engineer following a second visit to the gearbox outfit is as follows: "The Gearbox centre have just called; they are certain that the gearbox is in direct drive i.e top gear. This would leave two possible other items - the rear axle which I am sure is correct or the torque converter which I had hoped they would be able to deal with. They do not think that a TC fault would give this effect but that an incorrect converter would. If they send it for repair the same unit would be returned in the same configuration. There are no identifying markings on the converter and they are matched to the engine characteristics". I will pass on the diagnostic test info, thank you, but we are both baffled as I am fairly certain that the original torque converter has not been replaced at any time.
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Post by enigmas on Jul 28, 2015 23:15:03 GMT
Richard I own a highly modified Mk3 and have also driven standard Mk3 P5s. The factory BW35 in these cars are very sluggish. They run fewer clutch plates than the V8 versions and also a valve body that likes to jump straight into top gear and stay there. The box runs a front and rear pump but the front is the smallest of the 3 available. Similarly the torque convertor. Of 3 available its the smallest. Due to this it has the most slip before it couples fully. Add to this, the car has the same final gearing as the P5B and it is obvious why powerflow is mushy!
If it's the original torque convertor the impellor and turbine blades may be compromised through age as the vanes aren't furnace brazed but a rebuild can sort this.
The stator shaft being the smallest of the 3 available also can have several stripped splines. This leads to other problems with torque multiplication issues of the convertor.
You can upgrade the original box with a better valve body and more clutches. Have the torque convertor rebuilt for improved coupling. The angle of the internal vanes need to be altered.
I suggest you bite the bullet and have the box and convertor rebuilt by someone who knows these cars.
Contact Harvey on this board he's probably your best option. Tinkering with it peripherally won't improve the original box's performance.
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Post by richardjones on Jul 29, 2015 7:53:44 GMT
Enigma, thank you for your suggestions. It sounds as if I will need to go down the route of a strip down and rebuild and will contact Harvey as you suggest for further advice.
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Post by harvey on Jul 29, 2015 11:56:41 GMT
ISTR that the car is on the road, so if you want to find out what's happening, rather than getting information secondhand via a garage passing on results from a third party, I suggest you get the car back, and discover what's happening for yourself. I can't really make any sense of what you've been told. If you want to diagnose it yourself it will involve a bit of effort, and possibly some expense.
Make sure it is a BW35 by looking at the sump.
You need to eliminate the variables, so don't trust the speedo, and don't trust the tacho in the car (if it has one). Get a sat-nav to check the speed, (because although not 100% accurate, the chances are it will be more accurate than the speedo in the car, especially if that is the wrong one or geared incorrectly). Then get an accurate diagnostic tacho, connect it up and get the unit in the car with you.
Then roadtest in "D" listening for two upshifts, if you have those, it's engaging TOP gear. At that time check the speed and the tacho. If you can't feel the upshifts, start in "L" accelerate past the point that it should change into SECOND, then move the lever into "D" at which point it should shift into SECOND, when it does move the lever back to "L" and that will lock it in SECOND. Accelerate past the point it should upshift to TOP, move the lever to "D" again, and it should upshift into TOP.
Note the speed and rpm at all shift points.
Remember, this should be a 5 position selector box, if it's had the wrong valveblock or gearbox fitted who knows what you're going to get.
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Post by cstorey on Jul 29, 2015 16:07:07 GMT
Richard : where in the UK are you ? Before you do anything major you need to get the car seen and heard by someone who has some familiarity with them . The correct engine speeds under cruising conditions at 50 and 70 mph are 2200 rpm and just over 3000 rpm . If the car will do 70mph , then if it is stuck in intermediate i.e. 2nd gear , the engine will be revving its bollocks off and sound like it , no matter what the tacho says. If it sounds comfortable at 70mph, then the overwhelming likelihood is that it is in top gear
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Post by lagain on Jul 29, 2015 18:42:59 GMT
Castrol TQF is available on ebay and with free delivery !
I change mine every 4 or 5 years and always keep enough fluid 'in stock' for the next time.
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Post by harvey on Jul 29, 2015 18:51:00 GMT
Castrol TQF is available on ebay and with free delivery ! And the more people that buy it, the longer that it will continue to be available. |
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Post by barryr on Jul 29, 2015 22:22:22 GMT
The amount mine leaks I should be keeping production going on my own!
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Post by enigmas on Jul 29, 2015 22:37:52 GMT
If it's the original unmolested trans and torque convertor...it's more than an incorrect ATF issue!
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Post by richardjones on Jul 30, 2015 21:16:00 GMT
All, thank you for your suggestions. Tacho/Revs appear to have been the main issue as described below by my engineer:
"I have found the cause of the problem - the tachometer I am afraid. I and two others agreed that the reading appeared correct but it is not - it reads 3000 rpm at 1600 rpm which is the figure we were reading on the propshaft & so it is in top gear. The tachometer is different from that shown in the workshop manual & uses an inductive pickup from the coil feed, I have removed another wire which I now think was incorrect and had been added in the past in parallel to this but this does not effect the reading & there is no adjustment. The inductive pickup uses two coils of wire and this is original and depending on how it operates could change the reading if reduced but would then leave it under reading which I am not keen on.
>
> I can give you the following figures to calibrate it:
> Idle at 580 rpm reads 1100
> 3000 rpm reads 1600
> 4000 rpm reads 2300
I looked at replacement gauges (from the supplier of the oil gauge) but all I have seen are intended for cars with alternators. It was quite common on cars of this age to have the tacho triggered by the coil but not normally in the way yours is & they are normally quite reliable so possibly a secondhand unit could be found, it would need to be from a 6 cylinder engine. Alternatively there are a couple of firms who may be able to recalibrate it.
On another line of thought, and I think best not worried about too much now, with the corrected engine speed the torque converter does not pass it's stall test. This could be contributory to the gear changes being difficult to detect".
I guess with the rebuilt engine still running in, my guy wanted to avoid excessive revs whilst trying to diagnose the problem. I am now due to collect the car on Monday and will do some miles of my own before I have the head re-tightened. Replacing the tacho would appear to be the next job. I hope to see some of you at the Beaulieu Rally in September although you will notice that the paintwork/chrome is also ahead of me to sort out.
Any further advice will be welcome but I am looking forward to using the car for a few months during what's left of the summer. It will be over 34 years since I drove the car, then still owned by my father, on my wedding day. Did I say it is a white coupe`.
Many thanks. |
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Post by cstorey on Jul 31, 2015 9:20:44 GMT
I don't wish to be too harsh about your engineer but he really doesn't seem to know much about some aspects of this matter . The tacho is , judging by his description of two coils of wire, an RVI( Current sensing ) type which is precisely that shown in the manual, and it most certainly is adjustable by means of the potentiometer which is included in the circuit , and which on the vast majority of the Jaeger tachos can be reached through a small hole in the back using a small screwdriver. Usually the "screw" is a yellow plastic one . The tacho can be positively identified by the very small number which appears on its face which will start with RVI for current sensing and RVC for the later voltage sensing type . I am afraid that the change from one to the other has absolutely nothing to do with alternators at all which again causes me to doubt the engineer's degree of knowledge of these matters , as does his suggestion that the RVI type was unusual - it was virtually universal in the 1960s and continued to be fitted to the 8 cylinder cars which indeed had alternators . Also, quite how anyone of experience could mistake 1600 rpm for 3000 rpm is really rather hard to understand . Anyway, I am glad that you are at least partially sorted out, but I suggest you take the car to someone who has an independent tachometer to do the converter stall test - the one in the car, particularly one which plainly is not functioning properly, is wholly unsuitable for a stall test, which in any event I would be very reluctant to perform using an engine which has had no running in
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