Computer and transmission question

[mlgower]

Hi, This will be my 1st post here and I am a huge fan of this site. I have a question about the computer in my truck and how it is used to shift the transmission. I have heard that the earlier gm trucks used a speed reading to perform shifts of the transmission on the 4L60e and later that was changed to an rpm based shift points. I notice that on my 92 RCSB that it consistently shifts around 20mph, and 40mph (maybe 37), but if I am just creeping along, it will not shift sooner. My real question is, is it possible to upgrade or change the computer from the 92 that I have to say the 95, and would that make any difference? What else would I need to do to improve this? I could swear that I saw a thread on here somewhere talking about this, but I cannot find it. Any help would be appreciated. My trans seems to shift fine, although a bit hard from 1-2 unless I let up on the gas. I have a loud exhaust on it so when I am in a residential area, I like to keep off the throttle (although it is fun to set off the car alarms )

Thanks for the Great site and your help!!

 

[TylerZ281500]

they are some possible differences from the computers engine wise with those years. otherwise if they were the same then no. you can tune a computer to change shift poiints to a certain extent and so on with a 4l60e, not sure about the 700r4. i dont see swapping tbi ecms as a viable swap, if you want a newer style ship you can buy adapters to run a "better"(not the right word) chip in your computer. if you want an improvement do a 411 swap on a tbi and do coil per cylinder or something like that. swapping from 92-95 isnt really an upgrade.

All in all whats your purpose for changing shift points? just because it shifts hard? it may not be a computer oriented problem if thats what your trying to fix but rather transmission internals. do you have a 700r4? i know that my 4l60e will shift at different pints if you get on it harder, my 700r4 i had a manual valve body in it where i could shift whenever i wanted if i started in first and worked my way into overdrive.

 

[mlgower]

It has the 4l60e in it. I just find it annoying that it doesn't want to shift out of 1st until around 20mph or higher. it could be the trans, although it was replaced recently. the shift from 1st to 2nd is also pretty harsh..

 

[TylerZ281500]

my 1st-2nd is hard as well but i dont think mine shifts at 20.

 

[rhino]

Sounds like you have a good understanding on how it works... you are correct on the speedometer controlling the shift, kinda.
It tells the computer how fast the truck is going, BUT, the throttle position sensor, MAP sensor, and a few more also come into effect. If everything is working fine, the transmission will shift at a higher speed the more throttle that is applied. So, that's where I look when I have a unit shifting at the same speed at any throttle. The TPS. You can use a volt meter or scanner to watch the voltage. It should be around .50 at idle, then sweep up to 4.9 at wide open throttle. The 92-95 chevy's are bad about the TPS going out and doing this, very easy and cheap fix. Also, if you want a "cheap" shift kit, you can adjust the TPS to around .08-5.0 and it will shift a little higher. The higher the voltage, the more pressure on the pressure control solenoid

 

[rhino]

Great first post.... good to meet you

 

[mlgower]

Hi Rhino, thanks for the info. Yea, I wasn't happy with the TPS and replaced it, as well as the VSS since it was leaking. it still shifts a bit hard. I am starting to think there may be an issue with the transmission itself. I mean, it works ok for the most part, shifts good and solid, it's just weird. if I run it up to just before it shifts to the next gear, and back off the gas, the truck will nearly idle. it's like it's not holding it. then get back on the gas and it will rev up to the point where it catches and then goes. The last time I ran into this type of issue was on my 84 z-28 that had the 700r4 and The tranny on that went soon after. I am going to drop the pan this weekend and replace the filter and get some new fluid in it and perhaps some Lucas and see how that does. If I have to replace the tranny, it's no big deal, it just surprises me given how clean it is....