Shiftin into Overdrive

[mxunit13]

Any tricks or ways to get my tranny to shift into overdrive sooner? Im runnin 38's and overdrive doesnt kick in until about 55mph and it kills my gas mileage where I live. Any ideas?

[CSIPSD]

Ajust your speedo...

[Okiefromwatonga]

Change out the gears in the axle so that your over all drive ratio is the same as it was with factory tires

[CSIPSD]

Originally Posted by Okiefromwatonga

Change out the gears in the axle so that your over all drive ratio is the same as it was with factory tires

That will not command the trans to shift at the proper point. You have to ajust the Speedo to get the shifting correct.

[mxunit13]

Ok and is there any way to adjust the speedo without buying a speedo recalibrator?

[JSchuricht]

Find someone with a Auto Enginuity or ask the dealer to re cal it.

[dmd]

Originally Posted by CSIPSD

That will not command the trans to shift at the proper point. You have to ajust the Speedo to get the shifting correct.

Yes it will, if properly geared the speedo will be working properly. Then it
will shift at the expected speed.

Just changing the speedo will have it shift at the proper speed, but the
engine will be lugging at a very low RPM and not producing power. The
real fix is to get it geared properly for the tires. It will shift at the expected
speed and will have the proper RPM at the shift.

38's will kill you milage no matter what you do.

Minor tire size changes can be corrected with the speedo, but 38's are
a different story.

[mxunit13]

Im not to worried about it being in low RPMs, the truck has plenty of power to handle lower RPM'S which is why I would like it to shift sooner, Ive got a TW chip and some other mods that push the 38s with ease at lower RPMS, I know my mileage is killed with the 38s but running at 2200 RPMS alot of times instead of shifting into overdrive and running around 1400-1500 is killing it even more lol

[dmd]

At that low RPM after shifting you might have high EGT because of lugging. Cant
build boost that that low RPM. Chip just may make it worse.

[CSIPSD]

Originally Posted by dmd

Yes it will, if properly geared the speedo will be working properly. Then it
will shift at the expected speed.

Just changing the speedo will have it shift at the proper speed, but the
engine will be lugging at a very low RPM and not producing power. The
real fix is to get it geared properly for the tires. It will shift at the expected
speed and will have the proper RPM at the shift.

38's will kill you milage no matter what you do.

Minor tire size changes can be corrected with the speedo, but 38's are
a different story.

LOL... Tell me what part of changing the ring gear will change the size and speed of the tone gear (you know that thing that is bolted to the ring gear and what the VSS looks at).

Having it geared correctly is great and will bring back the power band, but will have no effect on when it shifts. You have to correct the speedo to do this.

AE is your best option for this, it can ajust up to 40" tires, unlike the dealer which can only go to 35"... You can also do your friends and anyone else you want.

Originally Posted by dmd

At that low RPM after shifting you might have high EGT because of lugging. Cant
build boost that that low RPM. Chip just may make it worse.

I ran 37's for years on 3.73's... Loved it. Wish I would have stuck with them or gone no bigger then 4.10's...