The Triumph Dolomite Club - Discussion Forum

How harsh should an auto box be when it engages?

Mine seems very harsh especially in reverse.
There is a solid clunk and the car judders. When it is running all of the changes are smooth and seem to occur in the correct place, in fact it is very impressive.

I have checked the fluid (replaced twice) and it seems to be at the correct level using Harvey's method.

I have set the idle , in neutral, a little high at around 900 because when I put it into gear it drops to about 500-600. If I set it lower it can drop to under 500.

i had a cortina mk2 auto that clonked in reverse,turned out to be worn rear uj on prop,changed both uj and it was gone and no noise,just a thought

900 rpm is too high for an auto.

750 max....then the jolt will go.

Jonners

Alan mine sometimes is harsh when selecting reverse, but is very smooth when going through the gears. I've changed the fluid twice in the last 2 months and this seems to of helped although it's still there, especially when coming to a complete stop and the box selects 1st gear. I found some receipts in the service history of previous owner / owners using fluid containing Dexron which is a definate no no! I'm just hoping the if the dexron has caused this jolt when changing down to 1st when coming to a stop that I've limited the damage to what it is now by changing the fluid to what it should be but as I understand, it takes 3 or 4 fluid changes to totally change fluid as most of it is in torque converter! Did you get your idling problem sorted?
Rich..

I've been adjusting the kickdown cable and this seems to have improved things all round. It seems to be the type of job where one adjustment puts another out (i.e. idling). but I am making small adjustments and I seem to be getting there.

It seems that this cable setting is very important for the correct operation of the box not just kickdown. There is quite a lot about this in the forum, and elsewhere so I suppose that I should have RTFF!!

What I would like to know is what are the symptoms of a slack cable (I assume that the main one is no kickdown) and , what are the symptoms of a tight cable (this seemed to cause mine not to want to change up and also made engagement harsher)?

Also what should the difference in idling speed be when the drive is engaged as opposed as to when it is in park or neutral. Mine seems to be 150 - 200 revs.

AlanH wrote: It seems that this cable setting is very important for the correct operation of the box not just kickdown.

Indeed it is, as is the use of the correct fluid.

AlanH wrote:What I would like to know is what are the symptoms of a slack cable (I assume that the main one is no kickdown)

Early upshifts, and the possibilty of slip caused by the lack of pressure. Loss of kickdown function. A slack cable means that at any given throttle opening, the line pressure is always lower than it should be.

AlanH wrote:and , what are the symptoms of a tight cable (this seemed to cause mine not to want to change up and also made engagement harsher)?

Harsh engagement, late upshifts, to the point where you need to lift of the throttle to trigger the upshift.

AlanH wrote:Also what should the difference in idling speed be when the drive is engaged as opposed as to when it is in park or neutral. Mine seems to be 150 - 200 revs.

That drop isn't unreasonable, but the state of the engine, and the type of engine will vary that. The lower the drop the better. Just remember that the tacho in the car isn't accurate enough to rely on.

I used to run a 59 Ford Zodiac with the old BW DG model autobox. this ancient and heavy but ultra smooth and reliable box only had a low gear hold so I deliberately over adjusted the kickdown ROD so I had to lift off slightly to allow top gear to be engaged. I had also made a few mods to the engine, big valve head, triple SUs, 6 branch extractor and straight through exhaust etc, so this trick helped the car respond to its increased power. It never gave any trouble during the 7 or 8 years I ran it like this and AFAIK it's still going, however I'm NOT going to recommend doing it to a 65 model which might not be as strong!

Steve

the possibilty of slip caused by the lack of pressure

When doing 50 mph the revs on the car are a bit over 2600(checked against my sat. nav. and timing light) .
Mintylamb gives the revs at 2414. I assumed that this was due to loses in the torque converter but could it be that I now have the cable too slack?

AlanH wrote: When doing 50 mph the revs on the car are a bit over 2600(checked against my sat. nav. and timing light) .
Mintylamb gives the revs at 2414. I assumed that this was due to loses in the torque converter but could it be that I now have the cable too slack?

I'd assume Mintylamb would take no account for any loss in the converter and just calculate the RPM at 1:1. The difference between those two figures wouldn't be any concern to me. If you accelerate in TOP initially the rpm increases at a greater rate than the roadspeed and the roadspeed gradually catches up, and that is because of the converter. It isn't like a manual.

By 50 mph and on a light throttle I would expect the transmission to have no torque converter slip at all.

You should therefore be using the figure for your diff and tyre size and 1:1 direct top.

On an 1850 this would be a 3.27. On a 1500 it could be 3.89 or 3.63 depending in age.

I suspect having the diff ratio wrong is more likely to account for your apparent discrepancy.

Jonners

I have checked the diff no. and it is the correct ratio. The tyre walls are 80.

I will ensure that I'm 'cruising' and check it again. If there is still a problem could it be the cable?

I just checked your sums...

50 at 2600 is 19.2 mph per 1000. Thats about the same as a Sprint auto (or manual) at 1:1 on a 3.45 diff.
50 at 2414 is 20.71 mph per 1000 rpm which is close to a 1:1 on a 3.27.

What diff do you think you have?

Doesnt look like you have any slipping.

Jonners