4l60e 1-2 shift does not happen at WOT

[JNJchev77]

..... until you let off the gas! Trans was rebuilt and only has about 300 miles on it.

I have a ported throttle body, CAI, Cam/Springs, and basically a "stock tune" I guess you could call it, from PSI. Also put a corvette servo in for shift firmness...
3.08 rear end, but computer is set up for 3:73 as I will be changing gears. Was told this wouldn't cause any issue with anything other than Speedo...

Would a tune help? Could this be a TPS issue? All other gears seem to shift fine and when I'm at about 1/2 throttle, 1-2 shift seems fine... I know very little about transmissions and have been researching and retaining what doesn't go over my head lol...

Thanks,
Justin

[BR3W CITY]

So if you floor it in 1st, it just rev's out first and never shifts (if you decided not to lift). The rear end gearing might make things a touch out of place, but only in the same sense that it affects the speedo. I.e., if the speedo is off, then the other things that use speed-based input will be off also. If lockup is set at 47mph, but you are actually going 37 when it happens, naturally things will fee off.

BUT that doesnt' sound like whats happening to you. Are you DBW or DBC?

[JNJchev77]

Well, it will shift, but it kind of glides/slips and then boom, shifts.. I haven't held it for too long lol

I'm DBC

[Super73]

As weird as you might think it is, I used to see this issue years ago on ls1tech and ls1.com with guys running ported tb's and ported maf end and not fixing the tune. Not sure what in the tune was doing it. Could be as simple as rpm coming up faster, bouncing off the limiter before the pcm recognises that both the rpm and mph limits have been met for the shift.

[JNJchev77]

Originally Posted by Super73

As weird as you might think it is, I used to see this issue years ago on ls1tech and ls1.com with guys running ported tb's and ported maf end and not fixing the tune. Not sure what in the tune was doing it. Could be as simple as rpm coming up faster, bouncing off the limiter before the pcm recognises that both the rpm and mph limits have been met for the shift.

Would you recommend dyno tune?

[Super73]

For a 1-2 shift issue the dyno will not help. Have your tuner fix you speedo first and see if it fixes the shift issue. If not have them lower the 1-2 shift rpm by 200rpm. If it still does it lower shift rpm by another 200rpm. If it is still doing it then there is something else besides mph/rpm points causing it to hold the gear too long.

[JNJchev77]

Ok, I have a local guy that I was referred too. I will try them and see if that works.

[BR3W CITY]

Also have them take a look at the shift firmness and the tq management settings.

If its slippy between gears (and its a known non-slipping tranny) then those two can play a role in the shift feel (but not the actual shift point)

[JNJchev77]

I just took it for a drive just to verify what I was feeling. At about 3500-4k rpm or so in 1st gear is when it stops pulling and seems like it should shift to 2nd, but rpm just keeps climbing until I let off the throttle a bit then shifts to 2nd. I ran it pretty hard this time and after a few passes I could smell a faint burning. Not sure if it was tire or fluid?

[JNJchev77]

Found this link when I was first searching the problem and couldn't find after to post here...

http://gmlongroof.4umer.com/t6394-common-4l60e-problems

Numbers 2,3 & 4 are all kind of similar. Would changing the TPS make a difference or because I'm not running stock components make this list irrelevant?

[BR3W CITY]

Put a meter on the tps and look at the voltage sweep. Keep your eye on 3/4-wot and see if there is a dead spot or jumping around etc.

In your above post, is that at wot? I would think it would shift higher than 4k wide open.
What happens if you baby it up to speed?

If the shift kit was installed improperly, line pressure issues, a problem with the piston, crap in the valvebody, or a problem with the spring(s) are all possible.

If you don't know whether it was tires or tranny....assume tranny. Pull the dipstick, see if its burned, and make sure there's actually enough juice in it.

[JNJchev77]

Originally Posted by BR3W CITY

Put a meter on the tps and look at the voltage sweep. Keep your eye on 3/4-wot and see if there is a dead spot or jumping around etc.

In your above post, is that at wot? I would think it would shift higher than 4k wide open.
What happens if you baby it up to speed?

If the shift kit was installed improperly, line pressure issues, a problem with the piston, crap in the valvebody, or a problem with the spring(s) are all possible.

If you don't know whether it was tires or tranny....assume tranny. Pull the dipstick, see if its burned, and make sure there's actually enough juice in it.

I will try the test on the tps when I get home.

No, that is not at WOT, that's at about 1/2 - 3/4ish, didn't want to kill something... just yet lol. If I baby it up to speed, it seems ok, but can still feel a little hesitation. Seems to have a little hesitation when it first shifts to 2nd also... I'm wondering if my Air/Fuel is way off?

No shift kit installed, but I did install the servo myself, seemed pretty straight forward. It was installed before rebuild.

I checked the fluid and it was still red/pink and didn't smell burnt. The smell was gone shortly after I parked it and wasn't present this morning when I went to the garage. Could have been that I just added a breather to the valve cover or that I was running it a little harder than usual. Fluid level seems fine...

[swb85]

I've been tuning LSx stuff for 10 years. Assuming you have a trans in good working order:
The part throttle shift tables in the pcm are all based off throttle position and VSS. So if your pcm is tuned for a gear ratio that you don't actually have, it's going to throw your shift points way off.

WOT shift points are controlled by rpm and VSS. For the pcm to command the shift, both the speed and rpm specified in the WOT tables must be met....so again having the gear ratio correct in the tune is imperative.

Any hesitation during shifts could be torque management pulling timing, again assuming a trans in good condition.

I wouldn't go hunting for problems until you're running the gear ratio the computer thinks you are.

[JNJchev77]

Originally Posted by swb85

I've been tuning LSx stuff for 10 years. Assuming you have a trans in good working order:
The part throttle shift tables in the pcm are all based off throttle position and VSS. So if your pcm is tuned for a gear ratio that you don't actually have, it's going to throw your shift points way off.

WOT shift points are controlled by rpm and VSS. For the pcm to command the shift, both the speed and rpm specified in the WOT tables must be met....so again having the gear ratio correct in the tune is imperative.

Any hesitation during shifts could be torque management pulling timing, again assuming a trans in good condition.

I wouldn't go hunting for problems until you're running the gear ratio the computer thinks you are.

In my initial post I said that the computer was tuned for 3:73. I "mis-remembered" lol, it's actually set for 3:42, but I have 3:08's now and will be switching to 3:73 in the next couple weeks. Once I have the new gear ratio in, do I just need to have the comp programmed for the new gears, simple as that? Assuming that the trans is good, that may solve my issue? I would think that any reputable shop should know what it needs...?

Motor is an '03. computer is aftermarket, if that helps...

[swb85]

Put your 3.73's in, have the gear ratio and tire height set in the computer to the correct values. If everything is mechanically sound and the tune doesn't have any wacky values in the shift tables then it should function correctly. If you have a copy of the tune file I'd be happy to look at it for you and verify there's nothing out of place.

[JNJchev77]

Ok.

Unfortunately, the computer and harness don't come with any "tune" information other than what you tell them. Gear ratio, tire height. Tire height is correct but gears aren't, obviously. I will get them changed.

Am I able to change the computer rear end gear with a programmer, or do I need to take it down to a tuner shop and have them do the work?

[JNJchev77]

So I have the computer set up with the correct gears, that are currently 3:08's. Truck is still doing the same thing. At WOT it just stops pulling at about 3,000 rpm but rpm's keep climbing. When I'm cruising at 20-25 or so and got to WOT, same thing... downshifts and about 3K, stops pulling, rpm's keep climbing...

Could it be a TPS issue?

Shifts fine otherwise, at 1/2 throttle. and fine at WOT for 2-3rd....

[BR3W CITY]

How does it rev in neutral? If you put a meter on the tps, it should be a pretty smooth sweep across the range...if it jumps, throws erratic numbers or goes to 0 then its most likely bad.

[JNJchev77]

Haven't rev in Neutral... but I'll check.

I forgot to test the TPS like you mentioned. I will do that and see what happens.

Thinking back last night, I did also have to replace the trans harness, after the rebuild because of a leak at the connector. For anyone that's had to do that you know there are a few parts that need to come out to get to the harness. I guess I could have put something back wrong, but I took my time, took pictures as I was removing things, and felt pretty good about it going back together... If the TPS isn't it, I'm going to take it to the trans shop see if they can figure it out...

[JNJchev77]

Called trans guy... He said it could be the pressure solenoid in the trans is bad...

But he also said to check the MAF and run MAF cleaner through it. I'm running a CAI with K&N that hasn't been oiled yet, well, because I don't drive it much right now just working out bugs.

So, if anyone gives a sh$! lol, I am going to test the TPS, clean the MAF and oil the K&N. If that doesn't do it I will take it down to the trans shop and have them check it out...$$$

Thanks for the help so far, everyone!

[JNJchev77]

Can anyone tell me if this is the pressure control solenoid for a 4l60e, 2002? I am pretty sure but need to be sure...

[clinebarger]

Yes that is the PCS solenoid.

[JNJchev77]

Thank you

[JNJchev77]

Well, I changed the PCS out last week and no change!

My fuel pump took a dump so haven't had a chance to really test it at 1/2 - WOT. New fuel pump and pre-filter going in tonight.

TPS tested fine but I've read it could still be bad, so I am going to change out TPS and VSS, only because it's cheap and easy... Also, should have access to a programmer to mess with shift points, gear ratio, etc, but want to change the sensors first to see if that helps...

[BR3W CITY]

What caused the pump failure? Were u running a pre filter before? If you were, consider that the pre filter itself can cause FP failure if it is too tight of a mesh, and not designed for pressure.