93 Yukon Lugs trying to go from 4th gear lockup to 3rd

[scott2093]

My old truck is just the opposite,just a little pressure on the go pedal makes the TCC unlock and just a little more pressure causes it to kickdown. I contribute that to a worn out 305 that never had any balls to begin with.

Are you referring to my 350 being worn out and it shouldn't act like this? That makes me feel a bit better. I do know when I set the timing advanced, it runs really great but, I was too lazy to go down the path of the pinging it caused so have kept it at 0... But it was fun, I don't remember paying attention to the 4th gear shifting situation as this was a couple of years ago.

A member I helped with his yukon has a pretty newish motor and transmission with 4.10 gearing and I noticed the same lugging in overdrive as well tbh.... but it moved great when it came out... but I was passenger so obviously can't tell 100% but we discussed as he was trying....

 

[Scooterwrench]

Are you referring to my 350 being worn out and it shouldn't act like this? That makes me feel a bit better. I do know when I set the timing advanced, it runs really great but, I was too lazy to go down the path of the pinging it caused so have kept it at 0... But it was fun, I don't remember paying attention to the 4th gear shifting situation as this was a couple of years ago.

Motor probably between 150k and 200k on it...maybe less.....I'd need to dig to find out when it was replaced by my friend who I bought it from long ago...Guess I forgot to mention it has a crate motor.....

A member I helped with his yukon has a pretty newish motor and transmission with 4.10 gearing and I noticed the same lugging in overdrive as well tbh.... but it moved great when it came out... but I was passenger so obviously can't tell 100% but we discussed as he was trying....

No,I was referring to my old wore out motor.

 

[scott2093]

Ah...

Just checked my tps and it's apparently all good....

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[PWC Repair]

Looked good with no dead spots.....check that off the list.

 

[scott2093]

So I took a screen grab video of droid while coming back from a trip to autozone... My son was helping and got tach added at 1:53....he'd never used the program so took a bit to find the tach when I was telling him to look for rpms...lol. Just after that, I put it in 4th, can see rpms drop, and tried getting it to get out of lockup a couple of times. Was 5 oclock traffic so couldn't really do too much.....

Before adding rpm to the screen I was driving in 3rd..
not sure if anything stands out? integer? Iac act right?....O2 sensor is new...

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[scott2093]

Writing in another thread about my past speedo experiences, I remembered that I have different gearing in my truck now. 3.73 from the 3.42 stock.

Do the proms have any programming different about them in this regard or is this all just taken care of when adjusting the vssb?

 

[df2x4]

I know the Vortec trucks have a setting in the PCM for differential gearing, not sure about TBI though.

 

[Scooterwrench]

93-95 uses a DRAC module that can be re-pinned or switches can be installed in it for gearing and tire dia. changes. It's a little white box over by the ECM. Right now the ECM still thinks you're running a 3.42 gear and is causing early shifts.
Here's a good explanation of the DRAC and how to re-pin it for your gear change.

Tradecraft Specialties

Specialized repair and troubleshooting

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[scott2093]

93-95 uses a DRAC module that can be re-pinned or switches can be installed in it for gearing and tire dia. changes. It's a little white box over by the ECM. Right now the ECM still thinks you're running a 3.42 gear and is causing early shifts.
Here's a good explanation of the DRAC and how to re-pin it for your gear change.

Thanks. I guess I wasn't clear at all. Sorry. I already have everything where it needs to be as far as changing jumpers and everything is calibrated but was wondering if that's all there is to it as far as the prom is concerned. I guess all it needs is the right signals from the adjustments. I was hoping to hear, "yes, you definitely need to find a prom that was programmed for 3.73 gears" or something...

 

[Scooterwrench]

Re-pinning your DRAC should be all you needed to do to calibrate the ECM with the gear and/or tire change. No matter what tire or gear you run the ECM needs to see 2000 PPM. You should be good to go!