dwb91lx

Thanks Tony, So the Drive gear must not be so difficult to replace after all on the AOD????... I called Mustangs Unlimited & the guy I spoke with recommended switching my 8-tooth drive gear to a 7-tooth & switch my driven gear to 21-tooth for the 3.73's. The black 23-toothers are too wimpy & lack reliability .

Tony71502

Not sure about AOD. Mine is a T-5. I doubt the 23 tooth is wimpy, they are all plastic, but the teeth may not mesh correctly. He is correct the drive gear should be 7-tooth, yellow.

dwb91lx

While I'm torn on the actual ratio (still) between 3.73's & 3.55's (easier speedo calibration) I would love to find the ultimate site to pick up Ford Racing Gear Set, Gear set install kit, & Traction Loc rebuild Kit (carbon version).

Which is the best install kit for gears (should I stay with Ford Racing? or what about Timken bearings)?

Is Royal Purple the best gear oil?

Will any of the big advertisers on this forum still do discounts for members???? Right now I'm leaning towards LateModel Restoration or Mustangs Unlimited.

nitrous_bob

there is only 1 answer

4.10's

i hate to be that guy that dogs on the peeps who "love" their 3.55's

but any gear for performance in an AOD car to boot, less than 4.10 is a waste of time

if you want economy buy a honda or a focus

thank you for looking at rpm's, typically you can see no more than 250 rpm's per gear bump but the torque you gain is disproportiaonatly bigger

literally the diff is a stock 3.73 car will bog...and a stock 4.10 car can lift tire

im just saying.....for an extra 2 bucks a week in gas.........????????

92LimitedEd

The gear ratios are a tough call. While I agree with Nitrous Bob on 4.10s, mine came with 3.73 (AOD). Now, I run a manual valve body on a built AOD (takes care of the 2nd gear issues) and I cruise 80mph at around 2750rpm... Not sure if 4.10s would put me in 3k range. I'm happy with the highway cruise and I have done 2 Hotrod Power Tours.

dwb91lx

So what would you do with speedometer calibration then?

dwb91lx

Bob, just curious how smoothly the AOD goes into it's 25ish MPH downshift to first gear with the 4.10s? Is that about 3,000 rpms? Thanks

mustangGT86_05

Yeah I wasn't even thinking about autos, but I have never driven one with an auto. I have heard multiple times if you run an auto 4.10s are the only way to go, glad I'm not so limited haha

dwb91lx

I did go with the 3.73's & the first thought was "should have gone with the 4.10's"...but don't get me wrong it is way better. It's still that lolly-gag skip through 2nd gear...My mech says do the T5 swap which will ultimately be the thing to do...He said he'd prolly charge $600-$700 (labor) to do it.
So the speedo is about 28% high-read currently with the stock driven gear (reads 85mph when really cruising 60mph)...I needed to get that reading so the speedo shop can make me a corrective gear box. I do have a black 23 tooth driven gear from Late Model Restoration & will see how close that brings it in...

dwb91lx

So by switching to 3.73's from 2.73's my '91 AOD speedometer reads 85MPH when traveling 60MPH (that's with the internally machined 8 tooth drive gear & the changeable stock 18 tooth driven gear).
I replaced the 18 tooth driven gear with the black 23 tooth driven gear purchased from Late Model Restoration for $14.99. That gear got it close enough @ a 66MPH read when actually traveling 60MPH (GPS)...
I will keep the 18 tooth driven gear for when I ultimately take the car to a speedometer shop, remove the 23 tooth & have it calibrated to the original 18 tooth. Should be a 28% reduction...then I don't have to worry about short-lived non-Ford teeth wearing down.