I have a 2000 Firebird with the 4L60E auto. I want to change the rear gearing to a taller gear from the stock 3.23 I read the FAQ about gearing and it was useful, but I still have a question for any of those that have done this on their 4th gen F-body. How and what did you do/use to change the values in your PCM for speed (mph) change, converter lock-up, shift points...etc Any and all help would be greatly appreciated.

 

You'd have to use HP tuners to adjust for the gear change.

 

It doesn't have to be HP tuners specifically, it could be any tuning software. Even a basic HPPIII handheld could make the necessary shift point and speedometer recalibrations.

 

Thanks guys, I have never used a HP tuner or any other tuner, Do they come pre-programed for what I want to do? I read up on the Hypertec one last night and it doesn't do gear ratios just tire size? Any suggestions of which one to use for a newbie?

 

Hypertech (HPPIII) does, in fact, also do speedometer and shift point corrections for gear ratio changes. Or, at least it always did historically - I haven't checked current production in quite some time but I can't imagine why they would have changed it. I can tell you first hand that the older ones 100% certainly offered this feature.

But there are a bunch of tuning options depending on your overall goals, budget and skill level. You can also just get a mail order tune to fix basic stuff like gear changes.

 

The HPP3 handheld I have for my '98 does have adjustments for both rear gear ratio and tire size. I dusted it off after sitting in the closet for 20 years to use when I swapped to an S60 / 3.73 ratio (I didn't change tires so didn't need that feature, but saw it in there). NOTE that the gear ratio selections seem to be limited to what gear ratios are available for the OEM 7.5" 10-bolt (its not an infinitely-variable adjustment...... unless there is an "other" selection that allows user input of the ratio that I didn't see).

 

Hey Johnny, thanks for that input. Can you tell me what ratios are available on your HPP3 for the 10 bolt?

 

It might be awhile since my T/A is currently in storage (but significant rain currently is making early driving days more likely). But I'll see if I can check and report back soon.

 

Looks like the Hypertech tuners have been updated a bit since mine was made back in the early '00s. Here is what they currently offer for a 2000 V8 Firebird:

https://www.hypertech.com/vehicle-re...x?AAIAID=27161

The "Speedometer Calibrator - Part #732500" says the following regarding gear ratio changes:

Gears 2.73, 3.08, 3.23, 3.42, 3.73 & 4.10

It would probably be more cost effective to just get a mail-order tune from a shop that does these cars. Then you could get some other basic stuff updated for the same price (if desired).

 

I wonder if these specific ratios is a PCM limitation or a programmer limitation? For grins and giggles, these ratios match the ratios of ring and pinion gears for the 7.5" (/ 7.625") 10-bolt (although I did find 3.55, 3.90 and 4.56 ratio sets as well) currently available from Summit. Most of the descriptions I found online of the HPP indicated you needed to plug in the programmer to your OBD-2 port to find what ratios "were available" on your car, leading me to suspect this is a PCM limitation. If so, not sure how to handle ratios that aren't on this list (unless a custom tune can "force" those other ratios).

 

My old hypertech (about 2005) had 2.73, 3.08, 3.23, 3.42, 3.73, 4.10, 4.56.

 

Custom tuning (even mail order) can be done for any ratio, as far as I know. Lots of folks with 8.8 & 9" rears using various Ford gear ratios and they've all been able to get a tune for it.