I have a 01 2500 HD with a 408 and a T-trim at 12 psi. It has a built PTC trans with a triple disc conv. The truck eases around great. All shifts are great except the 1-2 shift. No matter where we comand the 1-2 it wants to go to 6000-6100 hang there for a split second then shift. When it shifts it is firm. It is impossible to get the truck to 100% throttle without it spinning. Running the rpm down to 4500 seemed to make it worse (rev limiter tossed belt). Anyone have any solutions?
Just remembered some info that may be pertinent. We changed the first gear planetaries from a stock 2.75:1 to a HD 2.97:1
Stock planetary is 2.48Originally Posted by gdsims231
I wasn't aware the stock was 2.48. The new TCI planetary is a 2.97. Any ideas anyone? If I post a log and the tune would it help?
I didn't know tci made a planetary set lower than 2.75. Thats good to know...
1st gear wot shift is kicked off by mph, not rpm. If you haven't adjusted your speeds to reflect your different gearing and the slip of the stall, then that is likely your problem. You will also have to disable all relative tranny related advanced diagnostics to keep it happy with the different ratios. You can fix the gear ratios in the computer and keep from having to do that, just not with HPTuners.
Whats you rear gearing and tire height so I can steer you in the right direction?
Last edited by Bluecat; 02-02-2010 at 11:51 AM.
Damn thats awesome, but I just checked and that gearset is almost $1200 (wow). Would sure make 80 swaps in really heavy trucks a lot more bearable. I gather that part exists as a result of thier new 80 based 6 speed, because it has the same gearing.
Very interesting!! Thats the only reason i've alway's hated the 80e/350/400 cause of the tall first gear.
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Thanks Bluecat, we have checked the MPH allong with the revs/mile as I understand it shifts off of rev/mile and not vehicle mph. They matched so all is well there correct? I will have the tuner try turning off the advanced diags and see if that helps.
The change in the first gear ratio WOKE this truck up!!!! It is now freaky fun to drive.
I wouldn't put the new planetaries past 800hp. I don't think the 2.48 gearing is bad at all. Currently my car is a full weight 4th gen (guesstimate 4000lbs) with a 4l80 and a stock 5.3. the 3500 stall helps a lot though.
It helped this HEAVY truck out a ton. Its a 2500 hd 4X4 extra cab so it needs all the help it can get. It has a triple disc in it that will go between 2500 -3000. Why would you be scared of the new plantary past 800hp?
The higher the ratio the weaker the gearset (goes for pretty much any trans). Also in the 6 pinion carriers the pins start to get too close.
Point taken. The tuner is going to post the files and logs tonight. Would you mind taking a look at them to see if we are missing anything?
Go for it. That is what this section is for
Here is the file to the truck, the truck does shift. It just will spin past the commanded shift point and then when it stops spinning, it shifts into 2nd. We just want it to shift as soon as it gets the the shift point. 2-3 shifts great. Thanks
I blew one of those tci lower gear planetaries to pieces. I went to john kilgore, he guaranteed his to hold & I blew it to pieces, he backed out of his guarantee.
I now use a straight cut factory gear set.
I know what you mean, but they are getting harder to come up with. First the buses got depleted, then the bread trucks, now where looking for motor homes. The last straight cut 400 I seen sourced came from a old snapon truck.
Speeds definatly need to be lower. Assuming you want it to shift around 5800, Set the upshift to about 36 mph and go from there. Its hard to estimate stuff not knowing how loose the converter is and how it reacts to the power of the truck. But I figure 5800 @ wot in 1st is going to be around 41 mph. (No tc slip would be about 45) Could be even less if its a really loose converter or if its a really BMF. Id give the tranny a 5 mph head start and go from there. If it happens to early then you can start going the other direction.
Get me the converter specs and how much power you think its making and I'll post up my tranny spreadsheet with tables for you to paste into your tune.
With about 5% TC slip 5500rpm should be right around 40 mph.
I for one would like to see the spreadsheet, just because
Thanks alot guys. As far as power the truck has a Texas Speed 408 w/ a set of their 6.0L stage 3 heads. The heads flow 321 @ .600" lift which is what the camshft is. It is a comp 595 601 232 236 @ .050. on 115. The engine is 9.75 : 1 CR. It has a T-trim on it pullied to the max and makes 11 psi @ 5000. It is liquid I/C'd. I know it is a little undercamed, that the tune is mild (11*) and we are shifting it early, but this is a mans daily driver and the tune that is in it is more than sufficient for the handling, brakes....of the truck. As far as horsepower I guess I could log it and look at the fuel consumption, but I don't have that option at the moment. I know we have made 840 with a 377 at 14psi and 14* at 6500 in a m6 corvette. So I am GUESSING the truck would make somewhere between 550-600 the way it sits.
The convertor is a PTC custom triple disc. It is a stock housing with their modifications to the internals (modified sprag, strengthened fins....). It is around 2500 RPM +/- a little.
Anything else let me know....Thanks again.
I have tried zeroing out the mph and let it shift strictly off of rpm but it still didn't help. Is it better to just lower the mph a little?
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