About Overdrive.....

Topic: About Overdrive..... (Read 2485 times) previous topic - next topic

About Overdrive.....

November 13, 2004, 12:21:57 AM

I have and old cougar 85 with a newer v6. The car has the C5. I want a new tranny in the future. The T5 swap looks very good for the work required, but more possible for me its and OD transmission...but i saw what if i install and AOD transmission in a Normally 3 speed car, the engine wont accelerates good in OD or not produces enough torque to maintain a Cruise Speed (60 or 70mph), because the Differential (2.73) its a "long gear".....i want to know if the swap is safe from a C5 to AOD(any ford tranny) or i need some rear end modifications. Thanks...

Re: About Overdrive.....

Reply #1 – November 13, 2004, 05:37:07 AM

AOD 4th gear ratio: .67:1
2.73 x .67 = 1.8291 final drive ratio

215/70R14 tires (I'll go out on a limb and say you have something close) are 25.65 in. diameter

http://www.fordmuscle.com/calculators/rpm.shtml

1438 RPM @ 60 mph
1677 RPM @ 70 mph

I'm not going to post any solid conclusions from that.. I'll leave that to the others. I'm just posting the numbers for everyone to use.

Note to the others: Yes, numbers like that should sound familiar to a couple of you that I've debated my own project plans with. However, the differences are that I'll be looking to use a 3.55 rear gear and the second overdrive unit vs. 2.73 and just the AOD's overdrive.. and that I'm hoping to build one of my V8s specifically to work well at low RPMs (the proverbial "stump-puller") vs. using a newer V6. (stock, I'm guessing? I went through User Rides here and 10 pages' worth on the old board and couldn't find a thread from MexCougar saying more specifically what V6 and if anything was done to it) In other words, my partition is not an endorsp00get. :p

Re: About Overdrive.....

Reply #2 – November 13, 2004, 09:11:57 AM

overdrive is basically a highway gear, at low throttle input, and high speeds, usually 45+, the car will engauge into overdrive, to drop RPM's, reduce engine stress and increase gas milage

basically, its like having another gear added to your C5

Re: About Overdrive.....

Reply #3 – November 14, 2004, 12:12:15 AM

Well, with a "newer V6" i am refering to a different engine for the stock Cougar. Its from a Thunderbird 89, this is the only difference, but i guess its the same HP Oupot. I want the AOD because i do some Highway Driving and if its possible ill gain some Fuel economy, but my question is if its a correct Swap for the car without more modifications, and if its ok , what transmission do you recomend. Thanks....

Re: About Overdrive.....

Reply #4 – November 14, 2004, 07:00:22 AM

The concern here, I'm guessing, is whether or not that stock V6 makes enough power at that low of a RPM to pull the car along at 60-70 mph in OD.

According to the main site, the '89 V6 (non-SC) put out 140 hp @ 3800 RPM and 215 lb.-ft. of torque at 4000 RPM. Not sure how well it does at low revs, though.

Re: About Overdrive.....

Reply #5 – November 14, 2004, 07:28:36 AM

the main reason it puts out a different amount of power is due to the fuel injection setup, if its carbed using the factory stuff from a carbed fox car, it should be around 112hp, which is a bit shy of my 120hp out of my CFI'd 3.8L, and i have an AOD

i dont see an AOD being a problem at all

Re: About Overdrive.....

Reply #6 – November 14, 2004, 07:41:28 AM

But do you have an AOD with a 2.73 rear gear as well?

I have the '86 V6 w/ AOD.. but it's a 3.27 rear gear.

Here's how it changes things:

AOD OD (.67:1) x 3.27 rear gear = 2.1909 final
w/ 25.65 in. tires:

1722 RPM @ 60 mph
2009 RPM @ 70 mph

Re: About Overdrive.....

Reply #7 – November 14, 2004, 07:34:09 PM

I Need a different rear axle (3.08 or 3.27) to left the engine move effectively the car ?

Re: About Overdrive.....

Reply #8 – November 16, 2004, 02:55:48 AM

mmm, all seems to be a unsafe swap, i guess. Well, i believe that my next election will be a T5, because some of that trannys had a numericaly higher Overdrive gear (.75:1) and maybe my engine can produce the enough amount of torque. Only some questions about the T5...

1) Does my old base digital cluster still works with that ? (reffering to the speedometer)...

2) How many does my driveshaft can be shortened (and how much money it costs...)

3) Its a hard swap ?

4) How much money cost the entire labor done by myself (if i ruin the car , i will not to blame to others...)