HappyPappy

'90 4.0 L, AW-4. Will did the TC lock up bypass today, WOW, never had a tranny act that good. Now my question is Why wont it act like that without the bypass, what feeds the power to it, is the TCM shot, or do I have other problems??

Tried finding information on line, but that didn't work out,imagine if I took it to a dealer, they would probably say that isn't a Jeep part. There used to be a place in Atlanta that worked on that stuff, but lost there info.

I have done all the adjustments on the TPS, IAC ( both new),shifter switch shifter cable. The only thing now is it shifts hard into third. All the solenoids check out OK. Suppose I'll have to take it to AMCO and have them see what they can find, or run it as is.

cruiser54

What is the "TC lockup bypass"?

Firehawk068

Are you driving around with the TQ locked all the time with a "Bypass Switch"?
If so, NOT a good idea!


It is designed to lock only at speed, and light throttle loads, to help with fuel economy.


These trannys are not setup to shift very firmly from the factory.
You can add an aftermarket valve-body shift kit to firm up the shifts.

cruiser54

We need an answer to post #2.....

thatXJguy

It's something that bypasses the Torque Converter's lock-up functionality, isn't it?

Basically, you're shifting without use of the lock-up clutch, so it shifts a lot more dramatically instead of smoothly. (If my YouTube research serves me right).

canada_man

So before the the torque converter bypass, was the problem that you weren't getting any lock-up? I have the same year/engine/tranny as you and had no lockup when I bought it. Adjusted the white plunger switch attached to the brake pedal and have been enjoying my working tranny ever since.

HappyPappy

T C by pass (torque convertor) bypass lock up switch, No I don't run it unless it's in OD. Did a lot of research on the AW-4 and found a site that explains the whole process and diagnosis. Found out that the brake light switch is the only thing that controls "lock up". will be adjusting that later today. I don't think it worked since I've had it. I did remove that "anti-lock brake system" it came with and put a standard system on, thats when it probably stopped working. That site was "TCM for AW-4", about the 7th line down is a sub site 1-11, lot of good info there.
Thanks for your input and responses.

CobraMarty

How did you do the 'TC lock up bypass'?

Something doesn't seem right.
I have watched the shift and TC solenoids and the TCU is very good at controlling them.
On acceleration it shifts 1--2--3--4--4TC lockup, sometimes 1-2-3-3TC-4-4TC
The TC doesn't lock up in 1 or 2 gears.

cruiser54

Not entirely true. The TCU controls the Lockup. All the brake switch does is disengage the TC when the brake is applied.

What exactly are you trying to do?

Firehawk068

Torque Converter lockup is controlled by a number of things. (vehicle speed, throttle position, gear selection,etc....)

The only thing the brake light switch does, is disengage the lockup when you press on the brake pedal.

It is possible that if the brake light switch wasn't in the proper position, that you wouldn't get TQ lockup. (it would assume you were pressing on the brake pedal) But I'm pretty sure your brake lights would be on all the time.

Firehawk068

LOL...............Damn, Cruiser you beat me to it!

Firehawk068

My '96 will lockup in 2nd.
If I'm going up a long hill, and I manually shift it down to 2nd, and I'm above 40-ish mph, and I hold speed with part throttle, I can watch the rpms drop slightly as it locks the TQ.

cruiser54

Correct, if 2nd or 3rd is selected manually.

For clarification on switches:

CobraMarty

I'm saying when in OD/Drive position,
On mild acceleration it shifts 1--2--3--4--4TC lockup, sometimes 1-2-3-3TC-4-4TC

You gotta put a volt meter or a light on the solenoid wires to know for sure when they/solenoids are activated.
I wouldn't rely on 'my butt' or rpm drop to know when TC lockup occurs.

Firehawk068

Aaaaahhh, so there is a separate switch for TC clutch.
It looks like there is adjustment on that.
The brake light switch for '90 doesn't have any adjustment.

My '96 doesn't have the separate switch, there is a circuit in the brake light switch for it.