98jeepcher

Okay so my 98 xj will sometimes go into overdrive and sometimes wont. Well the other day out of curiosity i pulled up on the brake pedal well well overdrive kicks in as long as after i brake i pull up on brake. Then i went and did a search and found out how to adjust the brake pedal switch, so adjusted it and today no overdrive. My question is could the switch simply have gone bad or what? been searching for my problem for awhile and hope im onto something. Thanks

98jeepcher

Anybody?

XJ Rat

Hmmm, I know a guy who has the same problem with his 98. If it is not kicked into OD, he has to pull up on the brake pedal slightly. Messing with the switch did not help. He has ordered a replacement brake switch. Still waiting for it to arrive.

My 98 does not have this problem..............yet

98jeepcher

Well im going to pick one up today and see if thats it. Thanks hopefully it dont happen to yours

98jeepcher

Well i replaced it and nothing same thing as before. YAY. Now it just seems to be locking up in third gear or something. Im going to go to the auto store and get all my trouble codes and see what it is.

SilverfoxXJ

I know this is a very old thread , but I have this common problem of AWOL overdrive! I plan to wire directly from battery to dash switch, to brake switch, then direct to solenoid? I figure
this will give me an on/off switch on the dash and wiring through brake switch will work like normal?? Any thoughts on whether this might work?
I have done all the usual things NSS TPS Brake switch etc -used to get od when cold but once use brake, never comes back- now it does not come in at all ,yet solenoids and fluid is less than year old?

lawsoncl

Are you talking about shifting into 4th gear, or the torque converter locking up when in 4th. Just asking as you wouldn't be the first person to confuse them. Depending on the year, the switch for the transmission computer is separate from the brake light switch.

00t444e

The brake pedal switch controls the torque converter lockup not overdrive.

SilverfoxXJ

Thank you gentlemen! No I was not confusing it I don't think? However ,I do have 4th as a downshift to 3 increases RPM noticeably -
at 60 kph , I should run at around 1200 RPM with lockup ? This is what the old girl would run at in the beginning? (22 years ago LOL)

We are talking 95 sport aw4 /231 stock everything, except extractor manifold and big bore exhaust and cats, also a trans cooler, because in Australia
and RHD-, the trans lines go into the HOT side of the radiator (how stupid for a cooler) !
( Sorry - I have always called it overdrive, stems from growing up with a succession of Triumph TR's which of course are 4 speed manual with electric overdrive)
Maybe we should call it an anti slip device which in effect makes it a fifth gear?
(I may be a "Newbie" on here ,but have owned my XJ since 1998 and worked in the automotive industry until retiring a few years ago)

mcnerd

I am more confused.

Torque converter controlled by switch activated by brake pedal. If the switch is pressed in torque converter can kick in above certain speed. Depress the switch by pressing the brake pedal and the torque converter disengages.

Getting to 4th gear is a function of the TCU and the transmission itself to my knowledge.

So which function are you trying to control with a separate switch?

dave1123

The lock-up should work in 3rd gear if you limit the trans from shifting to 4th. It will engage at about 42 to 45 MPH. It makes a difference of about 200 to 300 rpm when engaged. It will drop out if you touch the brake pedal, but re-engage as soon as you release it.

If you want my honest opinion, the lock-up feature makes the engine run at too low an rpm to pull the necessary torque and not burn the exhaust valves. The 4.0 needs to run at around 1800 to 2000 rpm to make enough torque to pull any kind of a decent load without lugging. The terrain where I live is rolling hills, some small, some not so small. My WJ in 4th gear and lock-up runs at 1500 rpm at 55 MPH. It really doesn't like pulling hills at that rpm. I'll run in 3rd gear in those areas. Then it runs at about 1800, which it likes.

Please notice I'm saying MPH, not kph. BTW, I once had an MGB.

00t444e

Never heard of a 4.0 burning exhaust valves from lugging.

dave1123

Most of the time it's with the 0331 head with their small exhaust ports. The valves tend to run hot.

SilverfoxXJ

Guys, many thanks for all your input - but this old idiot solved the problem! I had about 1/8th gap between switch plunger and brake pedal!!!
Decided to replace the switch with a spare that I had and when I looked up I saw this gap! - I guess I could have re adjusted the switch but on
closer inspection it had been messed with too often, and I think it was able to jump back a couple of notches opening up the gap?
Because I thought it was ok, and the TCC had been locking a while back I was just planning to wire a switched feed to the lock solenoid?
It is now running like 1995 again!
For what it is worth -here in Aus, a new exhaust manifold was going to cost a thousand dollars plus labour! So I went to an exhaust shop who
supplied and fitted a whole new big bore system including cats for about 50 bucks more! 14 years later the head came off for oil weep problem
(which was gasket) we were really impressed as to the state of the exhaust valves and chambers! Seriously ,if you only ever did 3 mods to an XJ
it would have to be these- Extractor manifold and big bore system, -a trans cooler, and rear hood vents!!! Thanks again !

SilverfoxXJ

May have had a lot to do with that bloody antiquated exhaust manifold ? I mean 3 pieces with joiners! Really a bit vintage even in 1970's?
Interesting you had an MGB- I also had a 65 (first of the push button door handles)- I 'graduated" from a Mini Cooper S - biggest mistake ever!
you had to drive slow in an MGB so the girls could see who was driving! Cooper S mini,you were having so much fun driving,girls were the last
thing on your mind!!-
You may not agree but oh how I wish I still had that Mini !-
I currently have a 924 Turbo, a 308 cu Monza , My XJ and a Mazda 6 (daily) and a 1976 750 Triumph Bonneville ! Restored but it scares me now!