Trans control?

[DA BIG ONE]

Been tinkering w/vssb and a signal converter, diff gears are 3.42, I set vssb for 4.10 gears then hack speed signal to correct to 3.42 upshift/lockup @ 45mph will happen as if I still have 4.10 gears. Problem starts when transmission gets to operating temp then the gear changes are hard (extra firm) like there is an excessive pressure rise.

I have the TransGo off-road/towing mods and need to know what exactly happens when trans get to op/temp and what I can do to reduce firmness of shift?

[kaylabryn]

Has this been this way since you installed the Transgo or did it appear afterwards?

[DA BIG ONE]

Had the transgo first decided to tinker because no one makes a controller for my transmission and autotrac t-case combo. Even though I have 3.42's I'm thinking if I can get the whole thing to work like it has 4.10's up/down, shift/lockup, od lockup @ 45mph I'd get much better mpg.........................The banging of gears is like a full race manual shift 4L80 and I think it will destroy u-joints before long.

Some have mentioned lugging engine maybe an issue, so far no signs of lugging just tons of tq/power from idle.

[CapnAmerica]

FWIW...I have had that happen twice on my 1996 Sub 6.5TD (4L80E) and once on a firebird owned by my son (probably same trans--electronic, anyhow). In all 3 cases the problem was the ambient temp sensor (bad twice for me; disconnected for my son's car after some intake work). As you say, the trans felt like it wanted to tear the rest of the driveline out! The sensor is located in the intake horn on my truck and in the air filter area on my son's Firebird.

A thought as to the why (We engineer types always HAVE to ask why!): I believe when this sensor goes out, it indicates to the ECM that the temp is REALLY cold; therefore the trans fluid must be REALLY viscous, so it compensates with much flow/pressure as required as if you are running sludge in the tranny.

Hope this helps.

[DA BIG ONE]

FWIW...I have had that happen twice on my 1996 Sub 6.5TD (4L80E) and once on a firebird owned by my son (probably same trans--electronic, anyhow). In all 3 cases the problem was the ambient temp sensor (bad twice for me; disconnected for my son's car after some intake work). As you say, the trans felt like it wanted to tear the rest of the driveline out! The sensor is located in the intake horn on my truck and in the air filter area on my son's Firebird.

A thought as to the why (We engineer types always HAVE to ask why!): I believe when this sensor goes out, it indicates to the ECM that the temp is REALLY cold; therefore the trans fluid must be REALLY viscous, so it compensates with much flow/pressure as required as if you are running sludge in the tranny.

Hope this helps.


I have no problem whatsoever when cold its after truck gets to operating temp that the banging shifts start. I'm trying to understand what happens inside trans at the operating temp/banging gears point if anything to see what I need to adjust.

[CapnAmerica]

Yep--the problem is not when the trans is cold; it is when the oil is hot and the sensor THINKS it's cold. The problem does not show when it's cold, but gets worse as the trans and oil heat up. At any rate, if it were me, I'd jiggle the connector, and if that didn't indicate as the problem, then replace the sensor...it only costs around $12-$15.

[DA BIG ONE]

Capnamerica thanks for the input...........

[rjwest]

I think you are going where no man has gone before....

From what I read, you are forcing TCC lock up at very low RPM....
AND firmly, This may not be good for engine, do not think they are balanced
for this type operation.
From driving a std shift I noticed the engine to be quite smooth at RPM's below 1600,
not so with a auto, when I forced TCC lock up below 1500 rpm, I could feel the power pulses.
I do not think that the auto's are balanced for low rpm tcc lock up. That is why the
TCC unlock at around the 1600 rpm point.

( note dual mass clutch ) springs for dampening, vs viscous coupling )
just my opinion,,,

When I had my dually, I forced downshifts ( like a std shift ) and kept RPM's in the power band,

[john8662]

So, the trans is fine w/o the speedometer corrector installed?

Usually, almost always if the transmission is going into one of the many limp modes, which in this case is the banging into gears, it'll have some codes associated with it.

To get these codes though, you'd need to have a bi-directional scan tool to view everything including the history on the computer to see what's going on.

I'd like the project to work, as the 45MPH lockup is good for around town driving, where most speed limits are at near 45MPH. I'm also going to 3.42 from 4.10 in my burb (after getting another engine swap), in the middle of acquiring a front 3.42 differential, then I'll just swap out pumpkins, then have the gears setup in the rear.

J

[DA BIG ONE]

So, the trans is fine w/o the speedometer corrector installed?

Usually, almost always if the transmission is going into one of the many limp modes, which in this case is the banging into gears, it'll have some codes associated with it.

To get these codes though, you'd need to have a bi-directional scan tool to view everything including the history on the computer to see what's going on.

I'd like the project to work, as the 45MPH lockup is good for around town driving, where most speed limits are at near 45MPH. I'm also going to 3.42 from 4.10 in my burb (after getting another engine swap), in the middle of acquiring a front 3.42 differential, then I'll just swap out pumpkins, then have the gears setup in the rear.

J

Yes, tranny is fine if I hack the vssb to correct for 3.42 gears/33" tires shift up/down and lockup spread. When I leave the vssb set for 4.10's and hack just signal to the vssb to correct for 3.42's but controller is operating like there are 4.10's leaving all shift points and lockup like it has 4.10's everything is fine until warm up so I'm guessing the banging is somehow related to the trans temp sensor then whatever the controller is doing from there. No codes except for turbo control "I'm using mech boost control".

[rjwest]

Really confused but that's normal,

Only thing I now from trying a Toque lock,
is the obd2 Computer compares Tailshaft speed to Trans input speed.
If they don't match the parameters that the computer expects( for each gear and TCC lockup), it sets a hidden code and causes 'limp' mode,
IE: ' High Pressure shifts ' I don't think the temp sensor will cause a high pressure shift until 300 degrees, ( no book at present to verify )

So if you are changing the tailshaft speed ( rpm signal ) to computer
and not changing the input speed sensor ( I believe it is RPM, need book )
you will have a condition not within the computer parameters, therefore 'limp' mode, and
high pressure shifts,

That's my theory...

[DA BIG ONE]

Really confused but that's normal,

Only thing I now from trying a Toque lock,
is the obd2 Computer compares Tailshaft speed to Trans input speed.
If they don't match the parameters that the computer expects( for each gear and TCC lockup), it sets a hidden code and causes 'limp' mode,
IE: ' High Pressure shifts ' I don't think the temp sensor will cause a high pressure shift until 300 degrees, ( no book at present to verify )

So if you are changing the tailshaft speed ( rpm signal ) to computer
and not changing the input speed sensor ( I believe it is RPM, need book )
you will have a condition not within the computer parameters, therefore 'limp' mode, and
high pressure shifts,

That's my theory...

I've tried all aftermarket speed calibrators that hack signal to vssb and the result is the same banging of gears after warmup. I had e-mailed J_t when I tried to use their product and their response is it should work, however it didn't. The one unit that worked best was a digital converter which works w/most electronic speedos.

Trans temps never get anywhere towards 300deg.

I'm only guessing here but there are 3 speed sensors on my t-case which link to ABS, t-case control, trans control, ecm, and speedo have something to do w/issue.

[rjwest]

I think you are correct, Do you have a Laptop code reader ( like CarCode )
you may be able to read codes that are not available as diagnostic codes,
but part of the programing,

I went through the TCC lock up problem when I changed to 3.73 gears.
When Truck loaded , I was driving at speeds that put me in the TCC unloclk/lock ranges
and also 3/4 shift range, killed my MPG when loaded....solution , for me, was to force TCC
lock up and shift manually with a 4-3-4 shift sw...

I asked several PCM reprogramers about reprograming the PCM, no luck.

Did talk to a company ( ? , old memeoy ) that made a stand alone controller that was programable. Seemed to do all that was required to manage the 80Le, about 700 us bucks..

Finially I gave up and bought a Dodge/cummins std shift, ( it ain't no chevy unfortunatly )
cost a bundle to upgrade the suspension and other things..

Would have been cheaper to convert the chevy to std shift, But I do like the cummins
low rpm torque and 23 mpg ( best ) 15mpg loaded )

Good luck, if you solve the shift problem , you will be known as the 4l80e Mod Genius ..

If you need any specfic trans info, I will get my manual back and try to get info..for ya.