Hi I Have a daimler sovreign 420 automatic, I would like to know at what speeds and revs the gearbox changes gears because I am only having 2 gear changes on D1 and D2. On the highway I am only reaching 80kmh and the engine would be revved at around 5000 rpm, I am presuming that 1st and 2nd gears are only being engaged, I am missing the 3rd gear any idea what I can check on my BW gearbox please ? Thanks for your help

 

look at the dash corner for a switch that reads INTERMEDIATE SPEED HOLD IN / OUT.
If you have that switch, place it in the OUT position which is the same as OFF.

The switch controls a solenoid at the transmission that does not let it change to 3rd gear, ( the IN position), holding the transmission in 2nd gear, Useful for towing or climbing Mount Everest.

otherwise keep the shifter on D2.

 

Hi Jose, thanks for your reply, can you send me a photo of where this switch is found because I am not aware off it. As far as I know I dont have that switch, maybe I am wrong. It will be more clear if you can send me a Photo of this switch thanks

 

if your car has it, it will be at the corner of the dash as in the picture below:

 

This is it

 

ok, your car does not have it. You have a different transmission.

So if you drive the car in D2, the transmission does not shift to 3rd gear, right?? 5 thousand RPM is not normal, should be around 2,800 to 3,000 on 3rd gear at 70 mph more or less.

 

You have the Model 35 gearbox, the earlier one Jose was referring to has the speed hold switch. D2 should be the full automatic position and should go into third ( direct drive).

Unfortunately, I have not had one of these cars, but I would start by looking at the shift linkage and make sure that the transmission is actually going to the D2 position. You can check by rotation the linkage at the transmission and counting the number of stops or clicks it makes along the way ( the linkage might need to be disconnected to do this) and then with everything reconnected make sure that the transmission goes to the same place when you use the column shifter. I'm thinking perhaps the transmission is actually in D1 not D2.

Does it shift from 1-2 at normal rpm, i.e you don't have to go to 5000 rpm to shift from 1 to 2?

 

Jose is talking about the DG250 box which was in the early S Type. The 420 as Jagboi has states has the BW model 8 gearbox and does not have the speed hold. The set up I would think for the gear levers are possibly the same between the 420 and the S type and are made up of linkages from the back of the steering wheel under the dash to a cable that runs to the side of the gear box. Both ends have adjusters and there is a possibility as Jagboi has suggested that the adjusters need adjusting so the levers put the gearbox into the correct setting. It is a bit of trial and error I am afraid to get the settings right so what is shown on the dash is correct for the gear you are in at the gearbox.

 

The Sovereign has the BW Model 8 gearbox. The Model 35 can't take the torque of the 4.2 engine.
There is obviously a problem with making it change up to 3rd gear (top gear). Get a specialist to look at it or do it yourself if so inclined. It is likely just linkage, selector or cable adjustment required or a misunderstanding of the markings in the quadrant. If not it is a valve body issue which means a strip down.

Quote
"With the bigger engine came changes in the transmission. Although the all-synchromesh Jaguar manual gearbox standardised on S-types during 1965 had been designed to withstand the increased torque of the 4.2-litre XK engine, the optional Borg Warner 35 automatic gearbox was not up to the job. So the Jaguar engineers turned to a more heavyduty model from Borg Warner, the Model 8, and used this behind the new engine in the Mk X/420G and the 420/Sovereign. The new automatic gearbox brought with it new control options. The simple ‘D’ of the earlier selectors was replaced by ‘D1’ and ‘D2’ options. In ‘D1’, all three forward gears would be selected in the normal way, but ‘D2’ cut out bottom gear to give smoother (if rather slower) starts from rest and to prevent the gearbox from ‘hunting’ between gears in slow-moving traffic." unquote.

Source ~ Jaguar.

 

I suspect the gearbox is stuck in "kick down" mode.
This problem is extremely common in MK1 and Mk2 automatic cars where everything was done with rods rather than cables.
As the motor mounts got older and sloppier the engine and gearbox could shift and the kickdown would get engaged stopping the gearbox moving into top gear.
While I don't have a background in the 420 the failure to get into top gear certainly sounds similar.

 

I had wondered about a stuck governor, which is why I asked about the shift revs - then a governor can be ruled in or out of consideration.

 

Thanks the gears change at low revs when catching speed it is remaining revved up thats why I presume that 3 isnt being engaged, i will try and start with the easy bits you suggested, such as the linkeage and drop down cable yest again I need to remove bonnet and battery to do that, i will start with the linkeage setting because yes its not 100%. Thanks for your help , I will keep you updated when I will have some time to check this issue.

 

Yes ~ let us know how it goes. The kickdown is achieved by cable & governor. There is no pedal switch.

















replaced.

 

Oh! That's a TV cable style system. TV means throttle valve, and I can't emphasize enough how important it is to get that adjustment correct. That controls the line pressure inside the transmission, and if it is too low then the clutches will slip and burn up. I have seen a brand new transmission completely destroyed in under 3 km by not having that correct. This was on a GM car, but same principal applies.

I'd start by examining the shift linkage first, and once you have determined that is 100% correct, then move on to kick down.

 

Getting that throttle/kickdown cable correct is crucial to this entire effort. Get that right & the rest will come right unless damage has been done. Let's look on the bright side & get the cable right even if it means a new cable which one could have made up if availability is an issue. It's a Special Order at Barratts C26756/1 for a huge 129 Pounds. I would have it made up. That is a silly price for a piece of Bowden cable.

 

I have a similar model. I can't remember the RPM at different speeds, but it does seem a bit high on the motorway. However the gearbox has had a basic overhaul. The kickdown doesn't work properly, but the cost to get that going was about twice as much as a basic overhaul and I can live without it.
Note that a 3 speed box will only change twice. I.e. 1st to second and 2nd to 3rd.
I'm looking at changing the diff for one with a lower ratio for more comfortable motorway driving.

 

Lisa, If you're in the UK, the companies that rebuild Laycock overdrives also make a version that sits in the drive line. I've no idea of the practicality or cost of installing one in a 420. It might be a nice way of obtaining an extra ratio for high speed cruising without loss of low speed flexibility.

 

KEY PRODUCTION CHANGES

Although there were dozens of minor changes to the Jaguar 420 and Daimler Sovereign during their production life, few were of any major consequence. There were, however, two quite important changes. The first of these was a change of final drive on automatic models, from the original 3.31:1 to 3.54:1. This change was made during 1967, but in January 1968 the same change took place for cars with manual gearboxes, although the old 3.31:1 final drive remained available as an option. The second change occurred in August 1967, when the Powr-Lok limited-slip differential option was discontinued. There is some indication that these changes took place at different times on the two models: the final drive change occurred earlier on Sovereigns but the limited-slip differential option was dropped earlier for the 420s.

That change to the final-drive gearing was perhaps not entirely for the better. The new lower gearing certainly did help acceleration, ‘particularly in the 35–40mph range when Low is no longer available and Intermediate a little high’, as Autocar commented in their 8 February 1968 issue. However, Stuart Bladon, author of that report on the magazine’s long-term test Sovereign, added: At least for owners who drive fast, this [lower overall gearing] seems to me to be a retrograde move. Even with the 3.31 to 1 final drive used in this early Sovereign, the engine is turning at 4,450rpm at 100mph, and there is appreciably more engine noise than with the overdrive model. At maximum speed of 119mph the engine is beginning to produce quite a roar, and the rev-counter needle is well into the red segment at 5,300rpm. With the lower final drive, the maximum speed actually dropped, and engine noise levels at speed increased. Perhaps the real reason for the change was rationalization and cost saving: the 420 and Sovereign were the only models from Browns Lane with a 3.31:1 final drive, whereas the 3.54:1 gear setting was used in several other models of the time.
Credit James Taylor.

 

My auto S Type from 1967 has the 3.54.1 rear diff but it is marked up as 46/13 on an alloy tag attached to a diff plate bolt which when you divide it out comes to 3.538 so 3.54.
I would assume that the 3.31 diff would be marked up as 40/13 or close.

 

My 1966 S Type came with the automatic and 3.77 diff ratio. That was standard ratio for Canada/USA automatic cars. That was part of the reason I put in a 5 speed manual transmission, to bring down the highway cruising revs. The other reason was I bought the car as an abandoned project and the transmission had been disassembled the parts were in several falling apart cardboard boxes, the bell housing was cracked and I had no idea if I even had all the parts.