On changing torque converters for pleasure and profit.

I never tested the stall speed before I pulled the engine, but I do know I'd like the car to be a bit quicker from standstill.

Anyone fit an aftermarket TC with a higher stall speed, and how did it go?

In particular, did it remain driveable?

 

You have the 4L80 transmission? you should be able to get away with a somewhat higher stall (looser) converter because you do have converter lockup. I would not put a loose converter in a 400 transmission, I suspect it would be unpleasant in normal driving. The engine would tend to rev up and down too much sort of like a CVT transmission. You will also have this in the 4L80, but it will be eliminated when the torque converter locks up. No, I have not tried it. If I were looking for quicker take off, I would leave the transmission and torque converter alone and lower the rear axle ratio.

 

i put in a 2500-2800 stall. for the 3spd th400. the stock stall is between 1700 to 2000rpm. my 88 was 2000. transmission has to be taken off the engine and moved away to take the old one out and put a new one in. I rebuilt the whole transmission so thats why i went with a higher stall plus also a valve body upgrade / kit. my build tread will have details.

 

If you must... Here is what will work. You need a converter from a 1995 to 1997 XJR, it's slightly looser but still has lockup. You need at least 3:73 gears. Combined, this will help a lot but the 4l80e is still al lazy shifting SOB and the 1-2 shift will seem even worse (slower) than it feels now.

If you really want to get crazy, there is a shorter 1st gear for the 4l80e but its expensive and hard to come by.

Really isn't much low cost you can do that will matters all that much in the end, it's a design issue. Enjoy it for what it is or convert it to a manual. A manual conversion will be transformational.

The 4L80's tall 1st gear and tight converter are at play here. You already have 3:54 gears, An aftermarket / looser converter with out shorter gears will help somewhat at the expense of drivability and fuel consumption. A loose converters alone will make the trans feel even more slushy when it's not locked up. A loose converter will also increase fuel usage becasue the constant slip gets converted to heat not motion. The 4l80e is a strong but parasitic design, the converter is huge and heavy. Jags chose reliability over performance.

 

Yep, cheers @Rescue119 and @icsamerica, I'm pretty sure I have the 3.54 diff and not the 2.88. I don't really want to change the diff because, well, I'll have to track down a diff, and I already have the shorter one anyway - I haven't heard of any shorter ones available.

Shortening the first gear sounds likely to be what I really want.

However, while we're still kicking the topic around, I found this helpful article: https://www.novak-adapt.com/knowledg...tomatic/4l80e/

> First: 2.48, Second: 1.48, Third: 1.00, Fourth: 0.75, Reverse: 2.07

TCi make a planetary set with a 2.97 first gear, but it seems discontinued. I imagine about £1000 if I can track one down. Hmm, not sure if I want to go that high.

> The torque converter, in factory applications, is controlled by a PWM lockup solenoid for smooth lockup action. However, many performance enthusiasts prefer to reprogram the 4L80E to run as a simple on-off solenoid.

I wonder if I can hack that so it locks at ~2000 while driving, but not until 3500 when stationary! A "launch mode", if you will.

I am anyway contemplating a transmission control hack to give switchable full manual - I have in mind to put the shifter on a pivot on a longitutinal axis so I can bump it left/right to move through gears sequentially. There's a TCM called microsquirt which I understand is based on arduino, and I'm a programmer, so this is maybe not miles outside my field of expertise.

Not doing a manual conversion because 95% of the time I want the car to be a lazy barge. Just looking for ways to give the car a dual personality.

 

How does that work out on the highway?

 

higher stall and much lighter rotating weight, both helps accelleration, and engine response!

small dia. convertor 10" much lite weight! 700R4

 

no lockup but i can live with it with overdrive, 3.73 rear gear final ratio, ends up in OD 2.60 , perfect!
1 st gear in 700 ,,3.09-1, with my 3.73 rear , accell, AMAZING, and rips into 2nd boiling the tires!

 

pix

just havin fun

 

Quite right ronbros. Seen your car several times here. My goal is for the car to remain a distinguished luxury carriage but... with an undercurrent of latent brutality.

Where did you get a 3.73 diff? I doubt I'd spend anything for an extra .19, but curious as the canon is that there was only a 2.88 and 3.54

 

Dana 44 power lok, USA made in early XJS, 3.07 ratio, brought the xjs gears to a 4+4 shop ,counter guy took them into backroom, brought back a set 3.73 ratio ring&pinion gears ,$150. bucks!
checked with England cost ,wanted 1100. pounds!
what would you do at that point?
ron

 

Hmm, "go to a shop". I remember that!

I'm guessing diff gears are a lot less specialised than planetaries for a 4L80e <sigh>

 

Dana 44 rear drives fit thousands of USA trucks and Jeeps etc!
ron

 

"Bin there done all that" with the TH400, converters, shift kits, etc. The 12cyl manual 5speed is where the "fun" is, 2.87 first, 1.1 4th, 0.82 5th with a 3.54 diff. Fifth gear 60 mph= 1,800rpm. 70 mph=2,100rpm. Throw in an White Lighting shifter, aluminum flywheel & Bywater's enhanced computer and more FUN than any auto trans. Cons: no hole-shots or power shifts with that stock IRS & diff. or fun will be on hold.

 

i like the idea of the NEW GM 8L90E transmission, super low 1st and 8 of best ratios all the way to double over drive!
a good auto trans will out shift any manual trans!
like it or not Manuals are old fashioned !
to be honest when Jaguar was designing the XJ/XJS cars they never anticpated HARD Acceleration! DRAG racing style!
it can start to RIP the car apart!

 

To each his own. I was never one for fashion .

 

I was just looking at controllers for the 6r80 but I'm not sure how well it would FIT under an XJS, and anything beyond 6 gears requires stand-alone controllers that either cost thousands or havn't been developed yet, alot of newer stuff relies on the vehicle's onboard data network to do its function - the 6R80 allows for aftermarket controllers which isn't possible with all newer stuff.

 

a trans company just released a controller for the 8L90E, seen it on Utube!
probably not cheap,, altho nowadays nothing is reasonably priced any more !
some with plenty money , has 2020 C8 Corvette , and somehow burned up a clutch pack, only place in world ordered a performance clutch kit , $4000. dollars! for the parts not installed!
and they are located in New Zealand,,WTF?

 

>> 2020 C8 Corvette

Looks like it came in a cornflake box.

I had been vaguely wondering about swapping the entire trans, although it's money I hadn't intended to spend. But the more I learn the more I think it's the part that can do the most for the car.

@VancouverXJ6, about fit, these 6 and 8-speed units don't have more "gears", they just engage overdrive on every gear. IOW they use it to split each ratio, enabling taller spreads. The casting looks, by eyeballing pics on t'internet, _about the same shape and size_

Now all I need is a Mord Fustang that some princeling has wrapped around a tree. In fact, since they all end up wrapped around a tree, maybe I'll sneak out in the night with the oxy torch, it's a public service taking them off the road

 

you fried alright!