Slipping auto - Intermittent loss of drive

P

Peter Newbery

New Member
1971 Rover 3500 V8 Auto has recently developed loss of drive intermittently. First thing when cold it pulls away and engages all gears OK. Slowing to turn corner and climb hill however it changes down but loses drive. Guaranteed happening every morning unless I pussyfoot it in 3rd to avoid changedown.
Rest of the day it runs OK
 
First thing, check the fluid level, make sure that's correct, if not top up and try again.
If there's no improvement, come back and we'll try again.
 
hi peter,
first thing, check it COLD, never hot otherwise you will get a wrong reading as it will read higher up the dipstick.

ianp6man
 
It will give a higher reading when hot than cold, but correct procedure is to check when at normal operating temperature.
There are also 2 dipstick types, and use of the incorrect one will result in an incorrect reading.The flexible filler tube has the longer dipstick.(according to the workshop manual)
Unfortunately it's not worth consulting the workshop manual for the correct method to check the level as the book shows it in two sections, and one section is right, and one is wrong!
If you're going to use the manual, follow the procedure in the gearbox section, not the maintenance section.
 
I think you'll find the manual says check it cold.

Either way if its lack of fluid causing the problem it probably wouldn't read much on the dip stick warm
 
I don't know which manual you are referring to, but the factory workshop manual states "The final level must be set with the gearbox at normal operating temperature"
If you choose to do otherwise, that's your choice.
My choice would be, run up to normal temp, run thru the range engaging every gear, leave running in park, walk round, remove and wipe dipstick and then refit to check level. If you add fluid, run thru the range before re checking.

I don't think this problem is going to be fluid level related anyway, but it could be and it needs to be checked first.
 
I would suggest to replace tranmission fluid including oil filter which accessible by dropping the sump pan of the box...do this when trans is warm and not when hot (oil will spiral out rapidly and gets exceptionally hot)
on assembly,cleanliness is paramount...use a contact addhesive on the gasket surfaces and then torque back up as neccessary.after refilling carefully then check when trans is hot as harveyp6 mentioned.
if problem persists then pressure testing would need to be carried out along with stall test procedures
or simply take it to a transmission specialist who will have the correct data and testing equipment.
 
In this instance I dont think a stall test or a pressure test will tell you much. What appears to be happening is loss of drive on the 3rd to 2nd downshift, i.e. loss of second gear. A stall test done in drive is only testing 1st gear, and the converter. 2nd gear problems are normally associated with the front band or its operating servo or if not a loss of fluid pressure to operate the servo.
All of this is from memory so I'll give it some more thought, somewhere I've got the Borg Warner course papers so if needs be I can consult those. Its been a while since I've done one personally so I wouldn't say it's exactly fresh in my mind, plus I'm getting old and forgetful!
 
yes...but first rule of anylisis is to cover basics.no body has asked if the oil smells or is very dark in colour...this is basics...stall and pressure testing will reveal stator slip and valve block problems.naturally there is a and band adjustment. i tend to work in methodical way as to avoid back peddling later..the more information the quicker the correct procedure.
downshift cable? or more likely front band broken ,worn or servo,or internal valve sticking...?oil replacement will prove effective in helping to highlight the symptoms.
 
Just a quickie,

I had a Mk1 Granada auto that used to do the same thing. All that was causing it was a shot oil seal on the tailshaft. The oil was leaking out, and as soon as the oil level got low, loss of drive going round corners, or up and down steep hills.
 
Hi rich j, You are right about covering the basics first, but remember at the moment we don't even know if it has the correct amount of fluid in it . As i said previously, I don't think it's low fluid level anyway, but it could be, so check that first. low fluid level normally shows with delayed engagement of drive. Once the level is correct, do another road test, see if the fault persists if so move on to the next thing , which I would agree with you, check the colour and smell of the fluid.
There is only a manual front band adjustment on the very early boxes, and I don't think a 1971 V8 should be one of them. Having said that, the car is 35 years old so could have been fitted with anything in the past.
It is not recommended to use any type of gasket sealers or adhesives.Cleanliness is essential, and the only things recommended for re assembly are clean ATF and vaseline.
You are are also right about having the correct info. There is NO substitute for having the car in front of you, and a road test by someone who knows what they are looking for will tell you far more than a stall test.
Stall tests should not be undertaken if you don't know what you are doing. Generally if a box isn't shot before a stall test, it will be afterwards. It's probably a faulty front clutch or band.
My final advice at this stage would be,
1) get the correct fluid level (on level ground)

2) make sure the linkage is working as it should

3) make sure the kickdown cable is correctly fitted and adjusted.

4) then smell the fluid

5) if you then remove the sump, visually check what you can see inside the box, but if there is a lot of debris, remove and overhaul the box (the debris has to come from somewhere, and they don't usually heal themselves)

As a final note don't use DEXRON type fluids.
 
Well, thanks very much for all the input. I am impressed. Anyway, notwithstanding the difficulty I always experience in verifying the fluid level in the auto box of the P6, I will try again this evening. It's not dark in colour, still seems to be a nice pink colour. Trying to check the level is a nightmare. All I see is a wet dipstick that looks like fluid has sloshed all up it. Best suggestion seems to be to check for leaks and address, drain, fir new filter and refill with correct amount.
Again, thanks for the input. The P6 is my daily car and I've done about 35000 miles in it since 1997. Wouldn't drive anything else!
 
as mentioned ...never use a gasket sealant or rtv product upon pan gasket...particles can end up into the valve body and the end result is that car can decide to engage gear...seen them come of ramps. contact adhesive when used carefully is ideal for positioning gasket in place and is a satisfactory fix...we have been using that product on Bentley transmissions for years as suggested.
Also..never rev a auto hard in a stationary position unless there is someone on the footbrake for the same reason, mentioned above.Not a Rover thing,just a general bit of advice for anything auto
 
I would agree with the last piece of advice, I always treat any auto as tho' it could take off at any moment, it is unlikely, but it can happen. For that reason when they are running, I prefer to work over the wings rather than in front (or behind) the car. I just think I would prefer to maybe get hit by the bonnet and have my foot run over, than get crushed between the front of the car and the bench!
I once went to collect a customers car and when I arrived I couldn't help noticing the first ten foot of his precast garage was lying in a big pile.Curiousity got the better of me and I just had to ask, to which the reply was "I was giving my V6 cortina (auto) a tune up and it dropped into gear" so be warned, it does happen!
 
one of the funniest and scary things i have ever seen in a workshop was when a interceptor 7.2 being revved up at about 4000 rpm on a four post ramp, then deciding to engage first while poor little apprentice holding throttle open...dukes of hazzard jump followed,later by a funny smell within the cockpit..lol
 
Yes basics first Fluid Level, Colour, Smell even, is the Pump at all noisy ? Strange in a way, (as it seems O.K. after the initial "Glitch"). ???
 
Interesting harveyp6 is right, on the type 35 box the manual says check the fluid warm but the type 65 is cold - I'd only ever read the type 65 instructions
 
What is also interesting to see is that on the newly updated JRW website, a reconditioned auto box and converter is now priced at £650 plus a surcharge on your old unit and I presume VAT.
We all like a bit of profit, but that seems pretty steep to me!
Just goes to make my mate who does them look even more reasonable.
 
Value for money becomes apparent when you shop around.
When we got our P6B I noticed you checked the ATF at the opposite temperature to our P5B. Still a pain-in-the-rear job though. :;):
 
Sound advise indeed!

Shop around guy's, there are still bargains to be had. I bought 2 front wheel bearing kits for the P6 from my local motor factors cheaper than I could have bought one from a specialist!
 
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