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I just assumed the ‘TB’ as a likely code for the necessary vacuum connection to the GM400 series, David - which requires manifold vacuum to operate properly…
However, both carbs and the throttle body ‘proper’ may deliver ‘ported’ or ‘manifold’. The former varies vacuum directly by throttle position - likely inapproriate to GM 400 operation, considering the sensitivity of the alternative TV cable set-up. The latter in response to engine load…sort of.
Mechanical linkage, connected to the throttle pedal, sort of directly telling the box if the driver wants power or economy - and shifts accordingly. A vacuum connection is more like telling the box the load on the engine requiring shifting up or down. As manifold vacuum sort of reflects what the driver does with the throttle pedal - both systems work well enough…
That said, the differece between ‘ported’ and ‘manifold’ vacuum is an interesting subject in itself…
slofut wrote ‘TV cable’ and I assume he knows the transmission better than we do.
That aside, I have to do some thinking on the differences between vacuum and cable, if there are any.
Light throttle, full load and low rpm mean lower pressure, softer engagement despite high torque, than full power at full load and less torque/high rpm, whereas vacuum actually represents the torque output when you have the rpm information (pump speed)? The transmission is a blind, helpless mole in its dark tunnel and has to do a lot of guessing with its three or four inputs. So if the cable information is off, it might have consequences alright but I would try to match the range of motion and have a try
Yes David. The TV cable connects to the throttle linkage assembly. John’s kit provide a bracket to mate the GM TV cable to the stock Jaguar throttle linkage assembly.
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My mistake, Eric - not reading the original post carefully. I thought ‘GM400’ not reading TMH400 - which obviously is controlled by the downshift (TV) cable. Which of course needs some very precise adjustments…
So the old starter motor worked for a while, enough to get the engine started on the jig, but eventually a new one was needed. Easy, $70 at O’reilly’s.
I have connected the lock up solenoid wires as advised by YouTube for this post-87 transmission and tinkered a little bracket to get the TV cable to connect nicely and extend as needed with the throttle assembly.
Luckily, it seems that the travel of the GM inner cable is equal to the travel offered by the stock Jaguar throttle mechanism. I might put a spring somewhere in there though to not over pull the cable.
It goes underneath gm style and bolts to the adapter plate. That was an issue on my 420 with the aft hangin oil filter. Had a lawnmower size filter when I bought my car. Now converting to 4 speed overdrive transmission.
Looking good. You have a very clean engine bay. I have the kit in my 1972 XJ6 Series 1. Have you decide how you are going to control torque converter lockup?
I did the T700 in a’72 XJ6 years ago.
I couldn’t get the lock up to work via vac, how it’s supposed to.
So, I put a small switch on the shifter base so I could engage/disengage at will.
This turned out to be fun. You could “hold” lock up on, or run without, as I wished.
The 700 locks in 3rd and 4th, so you have 6 ratios to play with.
You could go; 1st, 2nd, 3rd, 3rd locked, 4th, 4th locked.
The XK engine las lots of torque, so locked in 3rd, and accelerating through 40-70 was a gas!
The downside was, if I left the switch in the lock up position, it engages at the earliest RPM, without regard to pedal position, as the vac-accuated would. But I’d just flip the switch back, and all is good.
If I was to do it again, I’d do the same. Although an auto transmission you can manually select all 6 ratios for a sporty ride.
Rob
