My truck is a 96 Crew Cab 1 ton 4x2 with the 6.5 diesel and 4:10 gears. The tranny works great except one thing got me puzzled. An example is:

I'm traveling at 70 mph in OD with the convertor locked, the engine spins at 2300 rpm. If I cruise at this speed (cruise control or not) everything is fine. If I let of the throttle the engine's rpm drops to about 1400, but the truck didn't slow down any. It seems like it went into N, but it isn't. If I step on it again it will go right back up to 2300. If I didn't have a tach I wouldn't even notice this is happening. It is totally smooth when I let off. Is this normal?

Dave

That freewheeling upon throttle lift is a normal characteristic of the 4L80E.

you cant have 4.10:1 and drive at 70 with the rpm at 2300, unless you have some MOSTER tires on the dang thing. We have a 4.10 rearend and the OEM 235/75r16s (dually) and at 55mph I'm turning 2200....with the torque converter locked and same tranny. You sure you dont have 3.73s?

you cant have 4.10:1 and drive at 70 with the rpm at 2300, unless you have some MOSTER tires on the dang thing. We have a 4.10 rearend and the OEM 235/75r16s (dually) and at 55mph I'm turning 2200....with the torque converter locked and same tranny. You sure you dont have 3.73s?
I have 245/75-16 and 4:10 gears. At 70 it spins 2300-2400.. Always did. The 1 tons in that year only came with the 4:10.

That freewheeling upon throttle lift is a normal characteristic of the 4L80E.
That's what I thought.. I wonder why it does that? maybe to help engine brake on the diesel?

Don't know why they do it but BD makes a module that keeps everything locked up on decel. This is especially usefull, actually mandatory, when you have an exhaust brake. Might want to check it out.

With the stock 245R75 16 I would see 2400 rpm. If you are getting 2200 at 55 then you must have 4:56 gear.

Greg

Don't know why they do it but BD makes a module that keeps everything locked up on decel. This is especially usefull, actually mandatory, when you have an exhaust brake. Might want to check it out.
Who carrys this piece? Thanks

Dave

BD Torq Loc

Nice unit. My Father has/had it on his '95 Suburban. It gets hairy installing in on '97 and newer units....maybe BD got that straightened out though.

You are able to lock the Torque converter in any gear above like 26mph.

My wifes Tahoe(4L60-E) is a gasser with 4.10's and runs 2300rpms at 75. My 6.5 Tahoe(4L80-E) has 3.42's and runs 2000rpm's at 75. We both have slightly oversize tires about 1" bigger in radius than stock. Both tranny's have about the same overdrive reduction in 4th. Just for comparison. Yota, sounds like you have different gears than you think you do, or you have a tranny problem (2200@55) Doesn't seem right with the gear to speed conversion chart's I've seen

Double check the BD torqueloc I'm pretty sure in PWM controlled trannys 96+ OBDII it doesn't work .

Hope I am not stepping on anyones toes here. The torq loc can be found at www.bd-power.com (http://www.bd-power.com)

Not stepping on any toes at all, unless they changed it, I know several that have tried that and it didn't work for later model trucks, I truly wish there was one that worked, I would add a exhaust brake to my rig if it kept the converter locked. EXH brake useless without locked converter.

You could put a manual switch on the dash to keep the TCC locked when you want. You will probably need a pullup resistor to make the computer think that it is unlocked when it isn't requesting lockup. Otherwise, you'll get a 'lockup solenoid stuck on' code.

I have that on my '97 gasser (without the resistor), and it really helps with engine braking. I'll try the resistor. It does kee setting codes.

The PCM checks Input shaft speed against output shaft speed.
If the rpm differances do not fall whithin set parameters it will
cause either: A: MIL Light " TCC stuck on " ( TCC Forced on )
or B: A Limp mode ( Hidden Code ) which will force
" Full Pressure shifts "
" Turning IGN off/on will clear Limp mode

The only way I know to fool the TCC lock up is to put 110 ohms
in parallel with Tran Temp Sensor and ground ( through a sw. )

Thsi will make the PCM think there is an overtemp and
apply high pressure, and change TCC lockup charistics.as follows:

2nd gear TCC lockup at 28MPH 3rd gear lockup at 40 mph
and 4th gear at 50mph ( no Change here )above with ( 3.73 gears , mph shift point changes with gear ratio, as rear sensor is used to control shifts )

This allows 2nd gear TCC lockup, and will not unlock TCC
with throttle position ( downshifts will occur though )

I use this method with my Truck camper, But I shift manually ie
Downshift before downshift commanded and by feathering the throttle to educe Shock of " High Pressure shift "

Takes some getting use to, Like a STD shift.
Note: The Switch has a 1-2 sec delay in/out.

Wish I had the money for the Electronic Aftermarket controller.

Final note: Spoke to BD rep at Fl RV show: He says Torque loc works on all Chev ( NOT! ) All I got was " You must have done something wrong, I did not tell him that the BD engineeer
admitted to me that there was a problem with obd2 installations.

The only way I know to fool the TCC lock up is to put 110 ohms
in parallel with Tran Temp Sensor and ground ( through a sw. )
.
How would that look?

I cut back the wire at the PCM harness ( or use a snap on )
and added a wire , also same for ground at the PCM Harness,
Ran 2 wires to a switch in the panel
Switch has ( 2 )110 ohm resisters in parrell ( 55 ohms ( misprint above ) soldered to one pole
1 wire goes to resisters, 1 wire goes to switch.

IE : 55 ohms in parellel to Trans Temp semsor when switch is on...

I'll draw up something tomorrow that I think will satisfy the computer but still manually override lockup to lockup when the comp isn't requesting it.

I think I get it. What color is the tranny temp sensor wire?

will have to go look again,
If you have access to 6.2 6.5 L diesel page There ris a lot of info in forum.. " forum.dieselpage.com"

Cut the wire that goes from the computer to the lockup solenoid in the trans. The switch needs to be a double pole double throw toggle, available at any parts store. It has two rows of three contacts, and has two positions. Attach the wires as shown in the drawing. When manual lockup is on, the resistor should pull the computer wire high, which would be normal when computer isn't calling for lockup. If line was open, computer would code and say "circuit open on TCC".

Would a 22 ohm resister work? That is all my local Radio Shack has. They had the switch!:)

22 Ω should be fine. I measured the resistance of a solenoid to come up with 20, probably anything from 22 to 1000Ω or more would work.

How do you id the wire you cut into? Can you find the wire INSIDE the cab by the computer? Mine is a 99.

Unfortunately, I don't have a wiring diagram for OBD2. I believe your computer is in the engine compartment, probably on the drivers side inner fender. At least that is where it is on the gassers. Perhaps if you go to a dealer, they would let you look at the service manual for your truck. Our dealer is accommodating for things like that.

obd2 computer is behind the glove box...shiny thing with 3 big cables