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8 & 10 cyl Bristol cars Type 407 onwards - restoration, repair, maintenance etc

Did Bristols modify the Torqueflight

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Old 18-03-22, 03:51 PM
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Default Did Bristols modify the Torqueflight

Having discussed engines, standard or otherwise, my thoughts turn to the gearbox.

I have a vague memory that I might once have read that Bristols feared that the torqueflight would prove too sporty for a luxury car and disabled at least one feature thereof that enabled full performance and engine braking up and down all the gears. This seems an odd thing to have done, but bear with me - I quote from an article relating to the torqueflight as installed in Chryslers.

"The calibration strategy of the TorqueFlite was as follows:When the "D" button was engaged, the transmission would always start in first gear, automatically upshift into second and then direct drive or third gear. Kickdown into second gear was possible below 65 mph and into first gear below 30 mph. A closed-throttle downshift from direct to first gear occurred at 10 mph.When second gear was selected, the transmission would always start in first gear and automatically upshift to second. It would remain in second regardless of throttle opening until 70 mph, at which time it would upshift to third gear to prevent excessive engine rpm. Kickdown into first gear was possible below 30 mph. A closed-throttle downshift from second to first occurred at 10 mph. The provision for second gear operation allowed greater control in city traffic and hilly terrain.A selection of first gear had the transmission start and remain in low gear regardless of vehicle speed and throttle opening. If this position (first gear) was selected at speeds above 30 mph and below 65 mph, the transmission would downshift into second immediately and would remain in second until the vehicle speed fell below 30 mph. A that time, the TorqueFlite would step down to first gear.

The words I have highlighted are not reflected in the 410 drivers handbook and neither do they accord with my own experiences, some of which were recounted in my article Alarms and Excursions in the Alps in BOC Bulletins Nos 167 and 168.

Can anybody shed any light on this. Did Bristols modify the torqueflight in some way when it was installed in the 407 and subsequent cars?, if so how? and is it reversible?
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Old 18-03-22, 06:50 PM
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There are reports that Bristol modified the early, cast iron cased, Torqueflites to alleviate issues with the tail shaft bearings overheating. I am unaware of any significant changes to how the shifting operates.

There are options to change shift points with "shift improver" kits. I fitted one and later regretted it. It was advertised as giving crisper shifts and reducing slip but I found it rather jerky and more for racing than for a touring saloon.

You can also have the torque converter rebuilt to change the stall torque ratio but my feeling is that it was well suited to the cars as supplied.
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Old 18-03-22, 07:09 PM
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Some useful info here:
https://www.allpar.com/threads/torqu...ations.229966/
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Old 19-03-22, 12:36 AM
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I seem to recall that what they did was to disable the part throttle kick down option on the gearbox and If I remember correctly this was all down to how the linkage was set up, certainly my 603 will do it sometimes but when I changed to an Edlebrock carb on my 411 and its associated adapter kit we suddenly had part throttle kick down. I can understand why Bristol might have set the cars up like that for London traffic, but in the early 80's traffic light dash between traffic lights on Brighton seafront it was a useful feature to have, especially if a local Jensen was about, if the local Lincoln Continental driver lined up against us though we were in for a hiding, that thing could shift off the line so generally we used to let him go just to see his efforts to haul the leviathan in before the next set of lights.
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Old 19-03-22, 12:46 AM
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Default gearbox modifications

I refer you to a post started by Paul Robert on 1/5/20 about 3 to 2 part throttle kick down. The modification apparently made by Bristol on later 411 and 412s was to delete this kickdown as being inappropriate for a refined touring car. I first saw mention of this in a 1975 Motor magazine. The Roberts post clearly covers the issues. My 411 didnt have kick down from new but when added vastly improved the drivability of the car.
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Old 19-03-22, 01:45 AM
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Default Torqueflyte

These gearboxes seem inaccessible but I'd suggest getting the relevant Chrysler Master Technicians Conference handbook on eBay (yes, other sites are available).
These are super readable and tell you how to service, troubleshoot and adjust your 'box. And there are cartoons too..,
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Old 20-03-22, 04:54 AM
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Quote:
Originally Posted by peter dowdle View Post
I refer you to a post started by Paul Robert on 1/5/20 about 3 to 2 part throttle kick down. The modification apparently made by Bristol on later 411 and 412s was to delete this kickdown as being inappropriate for a refined touring car. I first saw mention of this in a 1975 Motor magazine. The Roberts post clearly covers the issues. My 411 didnt have kick down from new but when added vastly improved the drivability of the car.
Here's a link to the post torqueflite part throttle kick down - Bristol Cars - Owners and Enthusiasts Forum

Paul Robert concluded that Bristol didn't delete anything. It was just that the transmissions used by Bristol didn't have the 3rd to 2nd gear part throttle kickdown in the first place.

If this is correct and Bristol said that they deleted/disabled that function, then it may have been a bit of clever marketing to cover up the fact that they were using older transmissions.
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Old 20-03-22, 05:32 AM
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Kevin you may well be right. Certainly by the time the 411 mk5 and 412 were about the current Chrysler boxes definitely had kick down.
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Old 20-03-22, 06:59 PM
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I understand the torqueflight always had full throttle 3 - 2 kickdown, part throttle 3 - 2 kickdown was only introduced in the early 70s when it was perceived to be lagging behind Ford and GM in respect of this feature. Iíve no idea when this might have been introduced into Canada.

But talk of 3-2 kickdown and aftermarket mods doesnít address my question, which Iíll rephrase.

How did it come about that Chrysler drivers equipped with the torqueflight can select 1st and and the gearbox will engage 1st as soon as their speed drops below 30mph, giving all the advantages of engine braking from that point to virtually standstill, whilst when Bristol drivers equipped with the torqueflight select 1st the gearbox will only engage 1st when the car is already practically at a standstill?

(Only once the Bristol driver has virtually stopped and selected 1st will excellent full engine braking be available whilst he takes the speed up again as far as revs allow whilst remaining in 1st. If revs donít allow and he changes up to second heís back to square one and has to virtually stop again before the gearbox will engage 1st)

It strikes me as a very odd state of affairs
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Old 20-03-22, 08:39 PM
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Which model are you referring to, Roger?

I don't recall this issue on my 410. The manual gives maximum change down speed to 1st as 30MPH and if my memory is correct it would indeed select first from that point.
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Old 21-03-22, 02:32 AM
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The earlier iron clad Torqueflite A-466 used on the 407 and 408 Mk1 had kickdown just the same as the 411 with the A-727 Torqueflite, (the description of the kickdown function is exactly the same in the 411 Owners Manual).

Below 29mph from either 2 or D(3) it will kickdown to 1st. Between 29-60 mph it will shift from D to 2.

In both cases kickdown is actuated by pressing the accelerator pedal to the floor stop.

I don't believe any of the V8 cars up to and including the 411 had part throttle kickdown (PTK).

It appears from this thread on a Mopar forum that PTK was introduced in 1971 for the A-727. The A-904 Torqueflite had PTK from 1967, but I don't think Bristol used the A-904.

It's also clear that PTK requires a different transmission valve body, so any talk of Bristol deleting PTK is yet another Bristol myth.
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Old 21-03-22, 02:54 AM
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Something to bear in mind is that these transmissions may not behave today how they were meant to behave, if they haven't been maintained properly, including periodic adjustments to kickdown, bands, pressures etc. This can cause the transmission to hang onto lower gears too long or fail to shift down at the correct speed.

Also some may have been modified with an after market shift kit.
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Old 21-03-22, 07:42 AM
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Quote:
Originally Posted by Roger Morrall View Post
How did it come about that Chrysler drivers equipped with the torqueflight can select 1st and and the gearbox will engage 1st as soon as their speed drops below 30mph, giving all the advantages of engine braking from that point to virtually standstill, whilst when Bristol drivers equipped with the torqueflight select 1st the gearbox will only engage 1st when the car is already practically at a standstill?
Roger, which Chrysler are you referring to and which Torqueflite transmission does it have?

At what speed are you suggesting that Chrysler drivers select 1st gear?

In most, if not all automatics, you can't safely select 1st gear if you are travelling significantly faster than the max speed for 1st gear, because it will actually shift into first gear. In manual override mode the transmission won't 'wait' until the speed is low enough for 1st gear - if you select 1st, it will shift into 1st.

Are you sure you're not thinking of 2nd gear in a three speed auto?

If you want engine braking with a three speed Torqueflite A-727 (or an A-466) selecting 2 is the way to go. In town driving you're probably better off driving around in 2nd than D; the car will be much more responsive
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Old 21-03-22, 09:53 AM
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David C, Kevin H

Thanks for your responses

Mine was a 410, built 1968.

Yes, it would kick down into 1st gear if the pedal was floored at an appropriate speed, entirely in accordance with the handbook - that is not the issue Iím trying to get my head around.

When 1st gear was selected on a trailing throttle it would only engage 1st gear after Iíd brought the speed down to about 6 mph on the brakes. This is not in accord with the Chrysler literature, which indicates that when 1st is selected it should engage 1st when the speed is down to about 30mph. My recollection is that the Bristol drivers handbook did not match the Chrysler literature in this regard.

I did not become aware of the Chrysler literature on how the torqueflight was expected to perform until after I sold the car on in order that it could enjoy the travels it had become accustomed to. I am somewhat curtailed in regard to long distance travel now but my interest in things Bristol remains and my curiosity is aroused.

The car was as well maintained as it could be, by BCS, SL-J and ACCS, none of whom ever suggested that the gearbox characteristics werenít in any way up to Bristol standards. It bore the original engine and gearbox numbers. ACCS rebuilt the gearbox after the torque converter failed. I owned it for 20 years and it took us as far as Morocco, Transylvania and Montenegro and most points in between, very often the only V8 on Geoffs Travels, so I knew it inside out.

Roger
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Old 21-03-22, 10:23 AM
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I can't be sure but I think I remember that my 410s would change down to first if the floor selector was used at around 25MPH. I will have to check but haven't got the car at home at the moment.

It looks as though it is possible to convert early Bristol Torqueflites to part throttle kickdown if you can find the kit:

727 3-2 Kick Down Module (1966-69) - A&A Transmissions
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Old 21-03-22, 10:57 AM
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FWIW, my 408 has a 1962 Torqueflite that was fitted here in the USA. I don't know if it was modified from standard at any time but it definitely has a kickdown function.

David
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Old 21-03-22, 11:57 AM
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David C - Iíd be most grateful if you could remember to check this when you do have the car back
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Old 21-03-22, 02:05 PM
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Quote:
Originally Posted by David C View Post
I can't be sure but I think I remember that my 410s would change down to first if the floor selector was used at around 25MPH.
As one would expect at 25MPH or even 30MPH.

I'm not sure what happens if you try to do it at higher speeds. I have vague memories of accidentally momentarily selecting first gear on an A-727 torqueflite at higher speeds and I think the transmission would still shift down immediately, which puts the transmission at risk of damage.
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Old 21-03-22, 02:22 PM
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Quote:
Originally Posted by dwomby View Post
FWIW, my 408 has a 1962 Torqueflite that was fitted here in the USA. I don't know if it was modified from standard at any time but it definitely has a kickdown function.

David
David, I'm puzzled by your comment. Why was a 1962 Torqueflite fitted to your 408 in the USA? What transmission did it have beforehand?

The 408 (Mk1) for the UK market left the factory with a Torqueflite (A-466), which incidentally had kickdown in 2nd and D (3rd), just like the later A-727.
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Old 21-03-22, 02:25 PM
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Quote:
Originally Posted by David C View Post
It looks as though it is possible to convert early Bristol Torqueflites to part throttle kickdown if you can find the kit
Trans Go made one as well.
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