Hits rev limiter on 1-2 shift
11-05-2020, 12:24 PM
#21
Teching In
Is there a specific question I can ask the Tuner that might help you get an idea? I do remember that the old trans I had before it got replaced was set to change at 5600rpm leaving the 400 to complete the shift. I’m not sure what the mph was set to. He tried to lower it to 5200 to shift but did not work. That’s all I recall him saying as we were in the middle of it.
11-06-2020, 11:02 AM
#24
TECH Apprentice
I don't know his tuner. No idea who tuned it or who built the trans.
Not confronting anyone...just letting him know that whatever is being done...is wrong.
Take that for whatever you want to.
As for a why...the GM shift strategy looks simple when playing with the tables but the background activity is quite complex.
To boil it down...you need the "normal" shift table mph to match the WOT shift table mph. If you do not, you get discrepancies and all kinds of headaches.
Also...setting the MPH to 0 and waiting for the rpm to trigger the shift is not the right way to do it.
There are free softwares that can get you very very close on a base shift table and then you can fine tune from there. I would assume any tuner that charges people money for their service would be able to handle that.
You want the mph and rpm to be closely related. If at 6500 rpm you're doing 42 mph. Then thats what your table should represent. If you're at 6500 and the shift table is set to 25 mph. That isn't going to have the desired result.
Plain and simple the 1-2 shift is easy.
The band applies.
That's it.
Your accumulator setup isn't as critical as people think. Usually they over spring or over shim the accumulator and cause unnecessarily hard shifts for no reason.
The servo type and clearance matter but are also both quite simple.
Then, like anything else. Make sure the shift valve moves...and make sure you don't have a massive circuit leak...and it'll be fine.
If you have issues with the 1-2 shift...it's likely tune, band clearance, or trans build/assembly issue like a leak, cut seal, wide band with concave drum, etc etc
Not confronting anyone...just letting him know that whatever is being done...is wrong.
Take that for whatever you want to.
As for a why...the GM shift strategy looks simple when playing with the tables but the background activity is quite complex.
To boil it down...you need the "normal" shift table mph to match the WOT shift table mph. If you do not, you get discrepancies and all kinds of headaches.
Also...setting the MPH to 0 and waiting for the rpm to trigger the shift is not the right way to do it.
There are free softwares that can get you very very close on a base shift table and then you can fine tune from there. I would assume any tuner that charges people money for their service would be able to handle that.
You want the mph and rpm to be closely related. If at 6500 rpm you're doing 42 mph. Then thats what your table should represent. If you're at 6500 and the shift table is set to 25 mph. That isn't going to have the desired result.
Plain and simple the 1-2 shift is easy.
The band applies.
That's it.
Your accumulator setup isn't as critical as people think. Usually they over spring or over shim the accumulator and cause unnecessarily hard shifts for no reason.
The servo type and clearance matter but are also both quite simple.
Then, like anything else. Make sure the shift valve moves...and make sure you don't have a massive circuit leak...and it'll be fine.
If you have issues with the 1-2 shift...it's likely tune, band clearance, or trans build/assembly issue like a leak, cut seal, wide band with concave drum, etc etc
The following users liked this post:
Chevysil1500 (11-06-2020)
11-06-2020, 08:56 PM
#25
100% Redneck
I don't know his tuner. No idea who tuned it or who built the trans.
Not confronting anyone...just letting him know that whatever is being done...is wrong.
Take that for whatever you want to.
As for a why...the GM shift strategy looks simple when playing with the tables but the background activity is quite complex.
To boil it down...you need the "normal" shift table mph to match the WOT shift table mph. If you do not, you get discrepancies and all kinds of headaches.
Also...setting the MPH to 0 and waiting for the rpm to trigger the shift is not the right way to do it.
There are free softwares that can get you very very close on a base shift table and then you can fine tune from there. I would assume any tuner that charges people money for their service would be able to handle that.
You want the mph and rpm to be closely related. If at 6500 rpm you're doing 42 mph. Then thats what your table should represent. If you're at 6500 and the shift table is set to 25 mph. That isn't going to have the desired result.
Plain and simple the 1-2 shift is easy.
The band applies.
That's it.
Your accumulator setup isn't as critical as people think. Usually they over spring or over shim the accumulator and cause unnecessarily hard shifts for no reason.
The servo type and clearance matter but are also both quite simple.
Then, like anything else. Make sure the shift valve moves...and make sure you don't have a massive circuit leak...and it'll be fine.
If you have issues with the 1-2 shift...it's likely tune, band clearance, or trans build/assembly issue like a leak, cut seal, wide band with concave drum, etc etc
Not confronting anyone...just letting him know that whatever is being done...is wrong.
Take that for whatever you want to.
As for a why...the GM shift strategy looks simple when playing with the tables but the background activity is quite complex.
To boil it down...you need the "normal" shift table mph to match the WOT shift table mph. If you do not, you get discrepancies and all kinds of headaches.
Also...setting the MPH to 0 and waiting for the rpm to trigger the shift is not the right way to do it.
There are free softwares that can get you very very close on a base shift table and then you can fine tune from there. I would assume any tuner that charges people money for their service would be able to handle that.
You want the mph and rpm to be closely related. If at 6500 rpm you're doing 42 mph. Then thats what your table should represent. If you're at 6500 and the shift table is set to 25 mph. That isn't going to have the desired result.
Plain and simple the 1-2 shift is easy.
The band applies.
That's it.
Your accumulator setup isn't as critical as people think. Usually they over spring or over shim the accumulator and cause unnecessarily hard shifts for no reason.
The servo type and clearance matter but are also both quite simple.
Then, like anything else. Make sure the shift valve moves...and make sure you don't have a massive circuit leak...and it'll be fine.
If you have issues with the 1-2 shift...it's likely tune, band clearance, or trans build/assembly issue like a leak, cut seal, wide band with concave drum, etc etc
11-06-2020, 11:30 PM
#26
Teching In
I don't know his tuner. No idea who tuned it or who built the trans.
Not confronting anyone...just letting him know that whatever is being done...is wrong.
Take that for whatever you want to.
As for a why...the GM shift strategy looks simple when playing with the tables but the background activity is quite complex.
To boil it down...you need the "normal" shift table mph to match the WOT shift table mph. If you do not, you get discrepancies and all kinds of headaches.
Also...setting the MPH to 0 and waiting for the rpm to trigger the shift is not the right way to do it.
There are free softwares that can get you very very close on a base shift table and then you can fine tune from there. I would assume any tuner that charges people money for their service would be able to handle that.
You want the mph and rpm to be closely related. If at 6500 rpm you're doing 42 mph. Then thats what your table should represent. If you're at 6500 and the shift table is set to 25 mph. That isn't going to have the desired result.
Plain and simple the 1-2 shift is easy.
The band applies.
That's it.
Your accumulator setup isn't as critical as people think. Usually they over spring or over shim the accumulator and cause unnecessarily hard shifts for no reason.
The servo type and clearance matter but are also both quite simple.
Then, like anything else. Make sure the shift valve moves...and make sure you don't have a massive circuit leak...and it'll be fine.
If you have issues with the 1-2 shift...it's likely tune, band clearance, or trans build/assembly issue like a leak, cut seal, wide band with concave drum, etc etc
Not confronting anyone...just letting him know that whatever is being done...is wrong.
Take that for whatever you want to.
As for a why...the GM shift strategy looks simple when playing with the tables but the background activity is quite complex.
To boil it down...you need the "normal" shift table mph to match the WOT shift table mph. If you do not, you get discrepancies and all kinds of headaches.
Also...setting the MPH to 0 and waiting for the rpm to trigger the shift is not the right way to do it.
There are free softwares that can get you very very close on a base shift table and then you can fine tune from there. I would assume any tuner that charges people money for their service would be able to handle that.
You want the mph and rpm to be closely related. If at 6500 rpm you're doing 42 mph. Then thats what your table should represent. If you're at 6500 and the shift table is set to 25 mph. That isn't going to have the desired result.
Plain and simple the 1-2 shift is easy.
The band applies.
That's it.
Your accumulator setup isn't as critical as people think. Usually they over spring or over shim the accumulator and cause unnecessarily hard shifts for no reason.
The servo type and clearance matter but are also both quite simple.
Then, like anything else. Make sure the shift valve moves...and make sure you don't have a massive circuit leak...and it'll be fine.
If you have issues with the 1-2 shift...it's likely tune, band clearance, or trans build/assembly issue like a leak, cut seal, wide band with concave drum, etc etc
Second, I took the Truck back to the dealer where I got the trans installed and they called me today. They notified that this transmission which was supplied by my warranty company and installed by the dealer is a “faulty” transmission. Said the were able to “run the trans and “data log” And can see that the problem is in the Trans. ( I asked but they did not tell me an exact problem) They state’s that this is not the first time this particular company supplied parts for their customer and it turned out to be faulty. Now, once again, I am waiting to hear from the warranty company on what they decide to do. Have to wait for the adjuster to review the claim and make the call..
thank you for sharing those tips on the trans tune. When I get a tune again I will definitely have a little more knowledge to come with so I know what exactly the Tuner is doing. If and when I hear more on what the problem is I will post here in case someone else has the same problem in the future.
Thanks to everyone thus far that has responded to this thread! I have much respect for the wealth of knowledge each member brings to the table!
Respectfully,
ZK
11-08-2020, 10:15 AM
#27
Teching In
Small twist to the tranny situation. Shop is waiting to hear from Warranty company for solution. I have to get to work so so picked up the truck for now since it will shift normal as long as I don’t gun it. Drove the truck to work than on the way home I decided to test it out. Hit WOT from a complete stop and Boom, changed gear. At this point the trans temp was 104f. Came to another stop and once again it worked. Felt great, shifting from 1-2 at 45mph, with about 5500rpm. than, the Trans started heating more, hopped on the freeway to get home, tried again after exiting freeway than It would not shift, at this point the Trans was 168f.
Again, I’m not sure exactly what the issue is as the trans has not been opened up yet but felt this was worth noting to add to the ultimate diagnosis.
Again, I’m not sure exactly what the issue is as the trans has not been opened up yet but felt this was worth noting to add to the ultimate diagnosis.
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