Hard shifting aut box

rockdemon wrote,...
Is this a uk car or are you elsewhere? I only ask because Ron has mentioned upgraded parts in rebuilt australian boxes?
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Hi Rich,

I am pretty sure that Craig (74westy) lives in New Zealand.

It is true that Ford cars fitted with BW35 boxes from 1983 onwards in Australia had the Tx fluid spec change from Type F to Dexron. This is also borne out by Catrol's recommendation for transmission fluid in those cars. For transmissions built prior to that date, the recommended fluid remained as Type F.

I will write more about this later today, but I am running out of time at the moment, so I need to get a wriggle on.

Ron.
 
Hi Harvey,

Shifting fron R-D and D-R with foot on brake produces no clunking, just a slight jerk of the car.

I'll continue with the kick down cable and look for improvement. I have no crimp on the cable. Also I'll double check the idle speed..

Do I take it that I should progressively "flush out" the Dexron with Type-F, and this will take about four changes of fluid in the sump, even with these "updated friction materials". If so what impact could have on the installed friction materials if any? Ron may provide input on this. I don't have a problem with this I just want to get it right..

Hi Rich, I'm in New Zealand and this is an NZ assembled vehicle.

Many thanks.
 
Hi Craig,

Be very careful with the adjustments that you make to the downshift cable, as that has a direct impact on line pressure. If you run pressure less than optimum, that will negatively impact on the life of the friction parts, and they will wear out much more quickly.

I'll come back to you shortly on the Dexron / Type F discussion.

Ron.
 
Without wishing to be controversial, the evidence suggests that provided the friction materials are not of the early type, then using Dexron fluid will not present a problem. Ford, Castrol and my own Rover's transmission history supports that view.

Type F fluid has a higher coefficient of friction, so the shifts are firmer. I am aware that Type F can be used quite successfully in boxes designed for Dexron fluid, such as the GM 350 and GM400 transmissions. However, the converse does not apply. Dexron cannot be used with success in boxes that contain friction materials designed for Type F, as my Rover's transmission history illustrates.

So Craig, if you seek firmer shifts, then change the fluid and keep adding Type F. If you're able to siphon out roughly 4 litres at a time, then changing it four times with sufficient driving in between so as to ensure a homogeneous mixture will return around 93% Type F. Doing it a fifth time will deliver around 97% Type F. It is diminishing returns the more often you change it.

If on the other hand your're quite happy with it, and you know for sure that the parts are Dexron friendly, then leave well alone.

Ron.
 
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