4.10 Gear Swap With Auto Trans In 98 GT

[karskrazy]

Well I need a little help here guys. I swapped out the stock gears in my 98 GT about 6 months ago and ever since then it has had a delay in downshifting back into first gear after a stop. It has to sit almost 2-3 seconds before it finally goes back completely into low gear. It is also going thru the gears faster than it should be, as was expected with this rather radical gear change. The speedo is also out of sync as expected but I switched out the plastic gear in the tranny to the highest number tooth gear (21 i think) I could find from Ford racing, but even with that it is still about 10 mph off. I thought I could correct the majority of the problem by doing that, but no luck so far.

So, I am trying to figure out if it would be better to get a chip burned for this car or what? I would prefer not to spend a ton fixing this problem but I would like to make it a lot better than it is now. Since the speedo is not electronic I wonder if a chip will even fix that part of the problem. I have seen the Speed Cal calibrator part that Dallas Mustang sells to fix the speedo problems( I GUESS ) but I am wondering if I do that swap will that fix the shifting problems as well since it will be reading a more correct reading from the speedo gear or am I still going to need a chip to get the shifting part correct ? I am not concerned about harder shifts, only timely accurate shifts at the right speeds. Also will I have to go back and install the original stock plastic gear so that new calibrated part will work right, since they apparently calibrate the settings they give you to program it with using the stock components as a base line before adding the Speed Cal. Is that right ??

Any help in this area would be great. I am definitely open for suggestions and the easiest and best way to fix both my shifting and speedo problems. I love the 4.10 gears and anyone that has a fairly stock GT will love the difference the gears will make from a stop and they are still great at highway cruising speeds. ** Just in case you are wondering the things I have added performance wise are a set of March underdrive pulley's, Non-Cat Off Road H-pipe with Flowmasters, and a K&N filter. everything else is pretty much stock. Thanks in advance !! Kars

 

[Bubba Z.]

I'm in the same boat as you are in that I have a 98 GT AODE tranny except that I haven't done my gear swap yet (torn between 3.73s and 4.10s).

One thing I have done is a little research on this because I was a little concerned about funky shift points and I do have the DM SpeedCal in my car (I changed tire size and I bought it in anticipation of the gearswap). It would fix your speedo/odometer problem but I would anticipate that you need to reinstall the original speedo gear.

About the shift points, I called Superchips to see if one of their tuners would fix the problem and he said you can manually (with the program) adjust the shift points based on mph to your liking. He also said resetting the SpeedCal would change the shift points anyway. In his defense, I think he forgot that I had a '98. This would work on the 99+ with the electronic speedometer. I then called Dallas Mustang and told them my situation and they replied with a blunt "No!" -- changing the SpeedCal will not alter the shift points. Hope this helps.

So you like the 4.10s eh? Eventually I'll but some new gears in. My priority is a PI swap, eventually I'll do gears and wake up the tranny with a shift kit, stall converter and cooler. Then a custom chip to take care of the shift points/retune.