PCM and 3.73's

Will I need to get my PCM programmed for 3.73's for the tranny shift points or just the speedo or both. I have heard that the tranny won't shift right and it could burn it up if I don't have a tune done right away. The reason I'm asking is I'm getting my headers installed soon but was thinking about gears in a couple of months. I was going to do the tune for the headers as I have to save some more money for the gears.

Yes, you'll need to get the PCM reprogrammed for the new 3.73s for your 4L60E to shift correctly. About waiting on the reprogramming, the greater the gear change 2.73s to 3.73s (large change) would be more of a problem. However, 3.55s to 3.73s you could probably get away with it for awhile.

WD

Would it shift manually right until I could get the PCM done. I'm going from 3.23 to 3.73. I guess I could wait for the tune and run the headers without a tune. I was just thought it might be too lean with headers and a cai.

When I changed to 3.42 from 2.73 the car shifted ok unless I was wide open throttle. Then it would hit the rev limiter before shifting. I think you will be fine in normal driving until you can get a tune. If you go WOT you will probably hit the rev limiter. I used tunercat to adjust my shift points.

Yes, the WOT shifts would be a problem. Normal easy driving around town shouldn't be a problem.

Also, you correct the rear-end ratio and tire height first with the programming, then adjust the 1-2, 2-3 and 3-4 shift points for the best performance.

WD