Recalibrate 4L60E for bigger tires.

[Yukon98]

Just wondering if anyone has a good link to the dip switch mod that rectifies the transmission speed sensor output? I really dont want to pay $200 US for the Jet Accu-speed 50108 but dont want my trans to slip itself into oblivion and boil to death again. Currently running 325/65R18's and have to keep it in 3rd gear unless at highway speeds. Ive searched in here but cant find it. Thanx

 

[PlayingWithTBI]

I don't know if this will help but Richard (@someotherguy) just posted this about a dash swap, it shows how to install the dip switches.

http://someotherplace.com/info/clusterswap/cluster.html

 

[someotherguy]

Year model matters, but I'll ass-sume from his member name (Yukon98) it's a '98 Yukon. He's gonna need a programmer or custom tune or whatever it is the ODB2 guys use to recalibrate. No adding of dip switches gonna help him.

Richard

 

[98chevy2500SS]

If you have to keep it in 3rd gear, than it's your gear ratio more than it is the transmission. What is your current gear ratio? Swapping to a lower gear ratio will help the transmission, at least 4.10s or lower.

Also, if you don't already have one, install a factory or aftermarket auxiliary transmission cooler.

 

[Yukon98]

I do have an aftermarket trans cooler but the gear ratio idk. I've had her 2 years now and have not looked into this yet. I do recall the seller mentioning he had changed the rear end and it was bigger than stock (but this may not be true). It is 6 lug wheels. The speedo is way out about 30km= 19miles/hr lower than what Google maps says I'm doing. Is there any id tag on the diffs or am I opening it up to find out?

 

[b454rat]

Open up glove box n get the RPO code that starts with G. GT4 is 3.73s, GU6 is 3.42s. Those are most common. My 98 2wd Tahoe has 3.42s and is about perfect. Has bout stock size tires. My 96 Yukon is lifted with 33s n has 3.73s, feels like could use a lil more, but then I push lil harder on the gas n the whipple takes it from there lol. I’m doing an SAS on it soon, going with 35s and 4.56s. It sounds like the PO didn’t change gears but maybe put in the heavier rear.

 

[Jesse_Wenting]

Sorry but bit of a noob in this area; what problem does larger wheels cause for our transmissions? for reference I'm running a set of 285/75r16 on my 98 K1500 with a 4l60e. This jumped out at me because I'm about to pull and rebuild my transmission due to a 3-4 clutch pack failure

 

[b454rat]

That’s a not huge difference in tire size, as long as no heavy towing or hauling. Keeping it cool helps a lot.

 

[Yukon98]

Sorry but bit of a noob in this area; what problem does larger wheels cause for our transmissions? for reference I'm running a set of 285/75r16 on my 98 K1500 with a 4l60e. This jumped out at me because I'm about to pull and rebuild my transmission due to a 3-4 clutch pack failure

Too large of tires causes the torque convertor to delay propper lock up causing it to burn out the clutches. the output signal from the speed sensor needs to be modified to make it work same as if stock. kind of like if yo were to remove a catalytic convertor from the exhaust. check engine light comes on and computer goes into limp mode causing an eventual snowball effect of issues unless you install the trick plug that makes it think its ok and working fine. You should be fine your tires are not too big. anything more than 1/2in larger in diameter can cause problems. google tire size calculator and put in both sizes to see the differance.

 

[Supercharged111]

Too large of tires causes the torque convertor to delay propper lock up causing it to burn out the clutches. the output signal from the speed sensor needs to be modified to make it work same as if stock. kind of like if yo were to remove a catalytic convertor from the exhaust. check engine light comes on and computer goes into limp mode causing an eventual snowball effect of issues unless you install the trick plug that makes it think its ok and working fine. You should be fine your tires are not too big. anything more than 1/2in larger in diameter can cause problems. google tire size calculator and put in both sizes to see the differance.

To say that a converter not locking up burns the clutches isn't accurate. An unlocked converter creates a ton of heat, and the heat will do what it does to kill the trans. The only reason the trans is more hesitant to lock with larger tires is because of the increased load. The shift points move as they should, the truck thinks it's going slower so the shifts are at a higher speed than stock. Displayed shift speeds remain the same, but your speedo now reads slow. Plus the truck becomes gutless with no gear change.