Reverse delay

[harveyp6]

Have just had the replacement BW35 box delivered,complete with torque,flexi,dipstick,etc
My thanks to Brian-Northampton for picking up and transporting it!!
Its the 7FU 17221,which is the PRND21 type!!!
LUCKY!!
As I forgot to check that it wasnt the early PRND2D1L type first!
I can only hope that it all works ok when it comes to fitting it!
But the guy I got it from,has stated that it was all working fine before it was removed!!
I, or Brian,who sort of knows him, have no reason to not believe what he says is true!!!

Harvey!!!
The fault with my knackered,so called recon,BW65 box is the rear clutch/band drum is scored,and that lead to speedy wear of the rear band!
It lasted over the 12 months/12k miles warranty they gave me! JUST!!!
Would you be able to provide me with a replacement rear clutch/band drum,all ready to fit with piston seals all done?
Am just thinking ahead,about refurbing it,but I may do the 35 instead,as I am sure its just the rear band that needs doing on that!!
Dave

7FU is not necessarily going to be the PRND21 type, it should be, but after all this time they can get rebuilt with the wrong valve on the valve block. You won't know until you fit it, unless you look.


I have all the hard parts secondhand.

The rear band works on the outside of the geartrain, so if it's scored you need a new one.

I can install the seals into the drums providing a) I can get the seals seperately, or b) you buy a kit to do the box and send the seals with the drums, or c) you pay for a seal kit which I return to you after the required seals are used.

 

[Pilkie]

The rear band is totally knackered,almost down to metal,so a new set of bands will need to be fitted!
The geartrain is knackered. Are they available new? or would s/h do? Are they expensive?
Will see what transpires,and let you know what route I intend to take!

 

[harveyp6]

The rear band is totally knackered,almost down to metal,so a new set of bands will need to be fitted!
The geartrain is knackered. Are they available new? or would s/h do? Are they expensive?
Will see what transpires,and let you know what route I intend to take!

I would imagine that someone somewhere has a new geartrain, but how much you'd have to pay for one I wouldn't have a clue. There's nothing wrong with using inspected secondhand parts, after all, a new one becomes secondhand the minute you run the car up the road........

 

[Pilkie]

I have access to a few good precision engineering places!
Would it be viable to have the groves skimmed off?

 

[harveyp6]

I have access to a few good precision engineering places!
Would it be viable to have the groves skimmed off?

It is possible to have the geartrain put in a lathe and then to reface the outside of the drum, but as it's not something that is a normal thing to do it's difficult to know how much you could remove before the smaller size becomes a problem. I would think that would be more expensive than a good S/H one anyway.

 

[Peter]

I can't give you an exact time for the introduction of the later selector pattern, and even if I could most have been modified to it over time anyway. I did have one thought, in as it is a possibility that you're not getting what you think you are, in other words what you think is a loss of TOP could be a loss of FIRST and the 1-2 change is in fact a 2-3 change, which could be a consequense of using an early pattern box with a later selector pattern at the lever. If you have the PRND21 selector in the car, select "2" and pull away and see what happens if you don't move the lever.

I'm sure it's 2-3 change, so much rpm in 70 km/h for example, and I have tried to drive in "2" reved it and lift of throttle but no 3rd gear.

 

[harveyp6]

I'm sure it's 2-3 change, so much rpm in 70 km/h for example, and I have tried to drive in "2" reved it and lift of throttle but no 3rd gear.

High rpm at 70km/h would indicate being in second, and if you select "2" you won't get an upchange if you have the PRND21 box, only if you have the PRND2D1L (early) box but the later selector indicator plate in the car.

I suppose it's possible that you have 2 seperate faults causing the TOP and REVERSE problems, but I would think it's unlikely.
(A stuck 2-3 shift valve for the loss of TOP, and something else for the REVERSE delay.)

But I think that after all you've checked, the box is going to have to come out.

 

[Peter]

Today when I drived the car a few miles in about 40 mph I came to a downhill, then I put in "N" and let the car roll
so I came up in about 50 mph, put in "D" AND Third gear was there! Stopped the car and tested if "R" worked, and it did.
Then drived away again on "D", but no 2-3 shift, back to "2" and then "D" again then Third gear worked again.
I think I should do a fluidchange again and see what's happening before box goes out.
What do you think?

 

[harveyp6]

Today when I drived the car a few miles in about 40 mph I came to a downhill, then I put in "N" and let the car roll
so I came up in about 50 mph, put in "D" AND Third gear was there! Stopped the car and tested if "R" worked, and it did.
Then drived away again on "D", but no 2-3 shift, back to "2" and then "D" again then Third gear worked again.
I think I should do a fluidchange again and see what's happening before box goes out.
What do you think?

All upchanges are triggered by Governor pressure (rises with roadspeed) overcoming line pressure (which increases with throttle opening), so what you've done by coasting is artificially increased the governor pressure while simultaneously decreasing line pressure (by closing the throttle) so giving the maximum difference between the two (in favour of the governor) so triggering the 2-3 change.

This could mean a couple of things,
1) that your line pressure (kickdown cable) is adjusted up far too high, or alternatively, your Governor pressure is too low.

2) the 2-3 shift valve is sticking

3) something in the clutch itself is causing it to need a very high pressure to operate.

If you want to eliminate the clutch being worn and/or faulty you could do a stall test in REVERSE, if that's OK, then remove and dismantle the valve block to see if the 2-3 shift valve is sticking.

Be very careful doing a stall test, and don't be surprised if it causes the clutch to fail altogether.

When it finally selects TOP, if you accelerate hard, but not kickdown staying in TOP, is there any slip?

 

[harveyp6]

One other thing you could do, (and do this bearing in mind my post in another thread in which I say that running with the kickdown cable disconnected should never be done) would be to take the clevis pin out of the top of the kickdown cable, and run with it disconnected. :?

If you disconnect it, and then pull away in "D" using the minimum throttle as possible, gradually increasing speed, and then note the speeds of the 1-2 change, and then the 2-3 change. Using only light throttle you should be in TOP by about 20mph at the very latest.

No hard acceleration.

 

[Peter]

When it finally selects TOP, if you accelerate hard, but not kickdown staying in TOP, is there any slip?

No slip at all when 3:rd is in.

I did stall test both in "D" and "R" and that went well, 2000 rpm, no slip at all.

Disconnected kickdown cable, than I got no reverse, should it be so? Drived away, early 1-2 but no 2-3 at all.

It seemed like clutch is ok, I think, time to disassembly valve body!?

Maybe, maybe all this is because car not been used for at least 11 year's... and just have to be cleaned up. I hope so.

And thank's for helping me

 

[harveyp6]

No slip at all when 3:rd is in.

I did stall test both in "D" and "R" and that went well, 2000 rpm, no slip at all.

That would tend to show that the clutches are OK

Disconnected kickdown cable, than I got no reverse, should it be so?

No, but it does point to what I said earlier about the problem being a need for extra pressure to get the clutch to work.

Maybe, maybe all this is because car not been used for at least 11 year's... and just have to be cleaned up. I hope so.

Possibly, it's one of the reasons I never recommend fitting boxes that have been left standing.

You could try dismantling and checking the valve block, but there are lots of little valves and springs which obviously have to be reassembled in their correct position. I'd like to think you could cure it by doing so, but I have my doubts, however if you want to try, and after all your effort I hope it gets the result you've been working toward.

And thank's for helping me

No problem, I'm sure I'm enjoying it far more then you are, after all you're the one doing all the work!

I have to say it is more difficult diagnosing without driving!

 

[harveyp6]

I've re-read the thread from the start, as it's easy to get sidetracked along the way, and I think that what I said earlier is probably going to be the problem, and that is although the rear clutch isn't slipping (as shown by the stall test,) there is something that is making it difficult for it to engage such that it needs a far higher pressure than it should do before it will work. It may well be that the shift valve moves, but there is insufficient pressure available to operate the clutch. For the problems you have with REVERSE as well as TOP you would need more than one valve to be sticking, but only one fault in the rear clutch.

If you've made your mind up to have a look at the valve block, it's not necessary to dismantle the whole thing, once it's out the 1-2 and 2-3 shift valves are in their own seperate housing on the top of the block, so this can be removed and it's a far easier proposition to just strip and examine that rather than the whole thing, and for the sake of it I'd say do it, if nothing else, to eliminate it as the cause of the problem. If both were sticking then that could cause problems with TOP and REVERSE, because the 1-2 valve can cause a loss of REVERSE if it sticks on the downshift.

 

[harveyp6]

I have done some further research into how the fluid control side in the 35 box works, and interestingly enough found some paperwork from the factory course, a lot of which isn't in the factory manuals used by the manufacturers, and one very interesting point as far as this problem is concerned came to light, and that is that what I said about two valves sticking to cause the TOP/REVERSE problems which I said is possible but unlikely, there is a way that just the 2-3 shift valve could be causing both on its own.

Obviously if the 2-3 shift valve was sticky, it would affect the 2-3 change as you would expect, but,also the supply for REVERSE is routed through part of that valve as well, and although it has no effect on the valve itself, it's just a way of routing the fluid, should the valve be stuck in the wrong place it could stop or delay the pressure trying to get to the rear servo and operate the band.

Can't say I've ever had it happen, but there's always a first time.........

 

[Peter]

Now I've cleanup the valve assembly, no changes except I'm back to the beginning, no "R" when hot and no 2-3 at all in "D".
I put to much fluid in box today, level is 10mm over max-level. Should drop some fluid.

And when I tested today, suddenly something happened with ignition switch... when I should start the engine I came to ignition but not to starter position... now I'm tired...

 

[harveyp6]

Now I've cleanup the valve assembly, no changes except I'm back to the beginning, no "R" when hot and no 2-3 at all in "D".

Well it was worth a try!

I put to much fluid in box today, level is 10mm over max-level. Should drop some fluid.

I doubt that will cause any problems, certainly as far as testing for your problems.

And when I tested today, suddenly something happened with ignition switch... when I should start the engine I came to ignition but not to starter position... now I'm tired...

Have you wired the inhibitor switch incorrectly. Matched colours go on opposite terminals. Put it in "P" or "N" and swithch the ignition on and see if the reverse lights are on.

 

[Peter]

Have you wired the inhibitor switch incorrectly. Matched colours go on opposite terminals. Put it in "P" or "N" and swithch the ignition on and see if the reverse lights are on.

Yes, all cables in right position. The problem is in the ignition switch, could not turn key to starter position, only to ignition than it's stop.

And thank's again for all help!

 

[Peter]

As a last try before taking autobox out of car, I put a can of "Wynns Automatic Treatment" in box. Something happened, reverse works when hot, but not 3rd gear. Should drive a little more this week.

I could buy a autobox from a 1969 P6, but he don't know if it's old or new type, anyone having ideas?

Ignition switch fixed, some WD-40 and it work's again

 

[SydneyRoverP6B]

Hello Peter,

Can I say that I don't really think it is a good idea to put additives of any kind into the automatic transmission. It may well end up doing more harm than good.

It really does sound as if you need to bit the bullet and take the car to an automatic transmission specialist and let them remove it from the car, overhaul it and refit it.

In the end it will be by far the best option.

Ron.

 

[harveyp6]

WYNNS is really only a seal conditioner, so shouldn't actually do any harm, but most times it won't do any good either.

If you had started with the problem that you have now, (got REVERSE but no TOP) my first thought would be pressures too high.(Providing you have REVERSE when cold as well as hot.)

Bearing in mind that the 1969 box could be 40 years old it could be anything by now, the serial number is a guide, but no guarantee of the internals.

I still think the box will end up coming out though, I've seen nothing yet that make me want to change my mind.