Kernal

Went to the track yesterday, box is shifting at 4500ish instead of 6600. Launch is good then 1>2 at 4500 gets really sluggish as if im down on power, 3>4 same story.

Second pass same story, backed off so i dont hurt anything. Thought it might be going into lock up clutch so we put that up to 100kph/60mph.

Third pass same problem. Tested it out on the street, shifts perfect at 6600.

Fourth pass, no burnout thought maybe the box is getting hot as it was a hot day. Same problem.

On the way home tested it on the street, shifts perfect at 6600. Only difference is on the street im spinning through the gears whereas on the track I've got traction therefore more load on the box.

I am running a trans cooler with a fan, bypassing the radiator.

Any help on the matter would be greatly appreciated

mrvedit

It sounds like you have tuning software such as HP Tuners or EFI Live. Post a tune for us to look at.

Kernal

the tune has been the same for ages. this problem just started randomly.

mrvedit

Just a hypothesis, but I wonder if the trans is overheating and the PCM is therefore using the "Hot" shift tables which are often very conservative. I've experienced a similar problem where the PCM cuts power to the engine to enter "safe mode".
Since it sounds like you have HP Tuners, log the trans temperate. Maybe you have a restriction to the cooler or something; the log should help ID the problem.

Remember that all shifting is commanded by the PCM. The trans cannot shift by itself. Therefore if it shifted at 4500, it is because the PCM commanded it to.

clinebarger

This could make the trans heat, The radiator mounted cooler is very efficient contrary to popular belief, If more cooling is needed....Add a auxiliary cooler in series. But do not bypass the radiator.

mrvedit

I know that the many (most?) will disagree with that statement. This has been discussed many times including this current thread:
https://ls1tech.com/forums/automatic...r-set-ups.html

However I do think you need to re-evaluate your trans cooling especially if your logging shows a high trans temp. Are you sure your fan is working, that the lines are not crimped, etc?
What kind of lines are you running to the cooler?

clinebarger

Thanks for the link, I know this subject has been beaten to death before the internet existed....But here's my 2 cents anyway.
In my opinion, You can size a "auxiliary" cooler to cool the trans by itself but that takes a pretty large stacked plate cooler in the 35-40,000 BTU range with a "Cold" circuit bypass & fan.

All that when you could add say a 15,000 BTU auxiliary in series with the radiator cooler doesn't make sense to me when the point is to prevent the trans from overheating.

mrvedit

I don't have the equipment to test the two hypotheses and therefore don't have my own opinion. I read all the threads, have good memory and therefore summarize and/or list the consensus if any.
In the other thread, 01ssreda4 has over 17,000 posts, has tried it both ways and therefore his opinion counts for a lot. Also I know that soundengineer is extremely knowledgeable and as close to an absolute authority as we have on this forum. Although he and 01ssreda4 disagree on some details, they both believe that bypassing the stock radiator is better.

Nonetheless, lets get back to the OP's specific problem.

jblankenship

iTrader: (5)

I am bypassing the radiator as well. Two trans coolers. One tube and fin, and the other is a plate. Runs from trans to tube and fine into the plate style back to the trans. Both mounted on the condensor stacked on top of one another. My temps run at 125 all the time unless I beat on it very hard. And then it normally only tops at 165, this includes passes at the track spraying 200. Mine also short shifts the 1-2 at the track. It is worse on the first pass. Mine actually starts shifting better on the following passes. I also normally pick up one tenth from the first to second pass and then the car stays consistent. No idea what it does on the street as it is spinning.

jimmyblue

iTrader: (11)

Check your matted TPS voltage. Too high will put you in
a short-shifting fault mode, and will only set a light if you
stay in it for (10 sec? There's a number, I forget it now).
So you can have this without any codes, if you're pedaling
it off the line and lift at the trap you will slide in under the
timeout limit.