Hey all, this is kind of a long one so hang with me......

I'm posting this on behalf of my brother. He owns a 2003 SD, 7.3L PSD, auto tranny, 3.73 gears, sitting on 35" meats. It also has a 4" exhaust system.

A long while back he installed a Super Chip single program diesel chip. Worked great. Then he took that out and bought a Super Tuner, and started running the 110-horse program. A while later, he had to have the tranny replaced. Since it was under 36,000 miles, it was done under warantee. I don't lay any of the blame on Super Chips, but you know dealerships--they **** and moan if they find out its been modified.

So, about 150 miles after that tranny was replaced, the new one took a dump. I'll chalk that up to the replacement tranny being a POS, or the dealership FUBAR-ing something.

So now he's sitting on tranny #3, and has set the computer program back to stock. He would like to run the 70-horse "tow safe" program, but he's nervous about messing something else up, and the dealership telling him to take a hike if something goes wrong again. I said he should be safe to run *any* program, that the tuner isn't causing his problems. He's still skeptical.

Any ideas why the transmission problems? Could it just be the trannies were lemons? Tire size? Driving habits? All of the above? I also told him that dealerships can't tell if it has a chip by running a simple diagnostic code reader. Am I right?

Thanks guys!!

 

Hi KAS,

Well, you can't expect to be able to use monster tall tires, drastically reducing torque multiplication and increasing the load on both the engine and transmission as a result, then compound that by adding another 110 HP & 200+ lbs./ft. of torque to further punish the transmission - and expect it to live. That is a recipe for disaster and quick repeat failures.

Yes, you are absolutely right in that there certainly can be and have been numerous poor quality Ford automatic transmissions over the years - especially in their remans - but what is being done to that truck is definitely hurting that stock 4R100 transmission, there's no 2 ways about that.

He needs to do a gear ratio change to restore the engine back to turning the same # of rpms for a given speed that it was turning with the stock factory tires - those tall tires are vastly reducing the torque multiplication that transmission is designed to operate within. He also needs to reduce the power level he is pouring into it, AND not drive it like a hot-rod if he is to have any hope of holding a stock 4R100 transmission together.

That +110 HP program is NOT designed for constant daily driver operation - it is considered an EXTREME program, to be used for OFF-ROAD or racing purposes only. It's not designed to make a stock 4R100 transmission take a 50% torque increase and a big reduction in torque multiplication from way-taller tires (which increases load on that tranny vastly) all at the same time, and make it live.

Your brother needs to do a gear ratio change to compensate for those much taller tires, then install a device (which we carry if he needs a source) that will correct the resulting speedometer error, and *then* he can start using the 70 HP program. But make sure the gear ratio change is done (or go back to stock height tires) before he starts pouring the power on, and do NOT use anything more than the 70 HP program with those taller tires (even with the gear ratio change) if he wants that transmission to hold together.

I wish you both good luck,

 

Thanks Mike!! I'll pass the info along.

 

Hey Mike,I called and left message for you.Im KAS300 brother.The owner of the 2003 superduty.I did have the computer recalibrated,is that enough?

 

Hi Kruiser,

Thanks for dropping by.

If I understand your question correctly, no, I don't feel that having the PCM reflashed is not enough, my friend. But then I have no idea what changes were made, either. Our basic recommendations are listed above in my previous post.

If it's the speedo calibration you are referring to, dealership service departments generally cannot alter the speedometer in those SuperDuty trucks to make the speedometer accurate with those 35" tires by flashing the PCM with other Ford info - they can only recalibrate the speedo in the VID block for gear ratios & tire sizes that were originally offered by Ford on that model year vehicle - so any gear ratio or tire size that was not offered by the factory, they can't "compensate" for. And even if they *could*, that would not change the fact that you need a gear ratio change to restore torque *multiplication* - not just add tons of power, as that tends to exacerbate such a configuration's problems.

Any time you put taller tires on these trucks, if they are more than about 1 inch taller than stock, or more than about 32" tall, we recommend a gear ratio change so the engine will once again turn at least as many rpms for a given speed that it was doing stock. That is the only way you can get the load on that transmission & torque converter down - or put the stock shorter tires back on.

In your case, I think you are perhaps just pushing that truck too hard with an "improper" mechanical configuration - meaning the 35" tires with no gear ratio change to return torque multiplication back to within "normal" parameters, and then using the most powerful program, which is adding 200+ lbs./ft. of torque. That combination is probably contributing to rapid stock automatic transmission failure in that heavy truck.

All we can tell you is what we recommend you do to get that vehicle's mechanical configuration back in line (which is to do the gear ratio change and then correct the speedometer), and then once the mechanical changes are made - *then* maybe think about adding more power, by using a less powerful program in that 1705 diesel Micro Tuner, like the 70 HP program. The 110 HP program is NOT for any kind of "normal" use in a daily driver. It's an EXTREME program - the engine can easily take it all day long, but a STOCK 4R100 automatic transmissions cannot be expected to live in the Powerstroke diesels with a 200+ lbs./ft. of torque power gain AND much taller tires also causing a drastic loss of torque multiplication - thus drastically increasing the load on that stock tranny.

Good luck!

 

Thanks Mike, excellent in-depth explanation as usual. Since this is a Ford site, and to not lead anybody to believe this would be exclusively a Ford problem, would it be safe to say that, that with any truck under the same circumstances, the results would be the same (too much power + too much tire = tranny failure)?

And one more thing, just out of curiosity, what would have happened if this truck was a 6-speed? I would assume that other parts of the drivetrain would be failing more often--rear end gears, etc., possibly grenade the tranny too?

 

Yes, that would be a universally problematic situation I'd say - adding 200+lbs./ft. of torque and 35" tires using stock gears wouldn't help any of them.

A factory manual tranny probably would have lasted longer in that scenario, *if* he could keep the clutch, pressure plate, flywheel, etc. alive - but that alone wouldn't "cure" it. Slippage is slippage, whether it's in the TQ, clutches, bands, etc., of an automatic, or on the clutch, pressure plate & flywheel of a manual tranny.

The bottom line is, if you use significantly taller tires than stock, regardless of power levels or whether it's a manual or an automatic transmission, then you must also do the required gear ratio change to restore the engine back to turning at least the same approximate # of rpms (or more) for a given speed in "x" gear as it was with the stock tires, so that base torque multiplication is not altered radically, and thus no potential for those types of ensuing issues.

 

Awesome, thank you.