My newly build 51 shoebox kustom, rebuilt .030 over 302, 1984 lincoln AOD, 3.0 rebuilt mavrick reareand, been running great but gas mileage really sucks! Seems to hesitate between gears, 2nd to 3rd, 3rd to OD, have had it to 2 different shops to set the TV cable, each came up with a different setting.Ran the numbers on her today, 12 miles to the gallon! And that is mostly highway speeds.Any ideas?
My opinion is that with a 3.00 gear and O D trans, that the engine is running well below a efficient rpm, kinda dogging it,,Assuming the Od is maybe .25-.26 that would give you a final ratio in the low 2's .
I always ran 3.08 for rear end, and normally got 18ish. Whats your RPM at 70mph? Hesitation between gears is a problem, does it shift hard when it does or is it sloppy. If its sloppy, the cable is off, if its hard, its an electronic malfunction with the lock up converter... I have seen an irregular diode pattern out of the alternator play havoc with electronics like the converter
good point, its sloppy, non electronic OD, not sure how i should adjust the stop on the tv cable, move it futher out from the carb or closer in
AOD needs no electrics for lockup or overdrive. In overdrive the ratio is .67 to 1. Third gear is direct drive 1 to 1 ratio with no torque convertor slip. With 3.00 gears your probably only turning about 1500 rpm in overdrive. I agree with Joe H in that you'd probably get better mileage in 3rd gear.
#1: Get the TV valve pressure set right. It is not that hard, plenty of step-by-step videos on YouTube and lots of info here. If it is not right, you will burn the trans up pretty quick. And by pretty quick, I mean within 100 miles. #2: Your rear gear ratio is too low, You are probably running below your torque convertor's stall or lockup speed in OD. This causes the transmission to turn into a very inefficient hydraulic pump that creates way too much heat causing you to burn up gas and trans fluid. Fix those two things and report back to us.
i've actually been crunching numbers on the subject today doing theory for my 62 unibody set up. while 3.00 may not be optimal Ford put 5.0 and 4.6/ aod(e) in a bunch of stuff and it was effiecient enough. as said around town don't bother with od and you'll probably yeild better mileage. my digging is based on the only jag rear i have access to is the matching one to the front suspension in my truck from the same donor and it's 2.88. it's got me tossing either using a mark viii rear which is 3.08. or forgoing irs and running a 3.55 or 3.73 explorer rear. all this would be behind a carb'd 351 from a mid 80s f150 most likely....
The majority of later model Fords use a 3.27 gear set. I would verify the speedo and odo are accurate first thing. Download the Ulyses speedo app for your phone, it is real accurate.
Here is a gear ratio calculator that you can use to help figure out a proper crusing gear. http://www.summitracing.com/expertadviceandnews/calcsandtools/gear-ratio-calculator Sent via Illinois Bell Telephone Company's Car Radiotelephone
This video is from a member of the 52-59 Ford social Group many of us have done 302/AOD swaps in our Fords,check it out:http://www.youtube.com/watch?v=jZwsQViZilQ Also one of the best AOD sites is here: www.clickclickracing.Common rear gear ratio for Mustang & T-Bird AOD cars was 3.55's shift point for overdrive was between 45-47 MPH in my '91 T-Bird,bottom line you need more gear.
My "Special Construction" roadster has a '84 Crown Vic 5.0/ AOD with a 1978 Mustg II 8" rear end with ring & pinion ratio 3.00. Overdrive is useless driving less than 65 mph because the ratio is lugging the engine. Several vendors on eBay sell MOTIVE Gear Performance Differential Ring & Pinion for various Ford applications. Some ratios are:3.08, 3.25, 3.40, 3.55, 3.80. I plan to install the 3.55 eventually. Price is about $199.60, plus shipping.
My '54 with a 302/AOD at 70 MPH in OD is about 2450 RPM with it's stock 4.10 rear which was original behind the 223 and 3 speed w/OD.
Is the engine completely stock other then the overbore? You running efi or a carb? If carb what carb? Where's the timing set? Stock converter? The shifting sounds screwy to me. Almost sounds like more the a adjustment issue. My 87 mustang has a 2:73 rear gear with an AOD trans. Goes into od around 45-50 mph. I leave it on od position all the time and let it shift when it wants. The car gets around 19mpg
great info guys, gonna take it to a buddy of mine who has a tranny shop, best in town, let him check it out sounds like we are leaning to changing rear gears. It is a carburetored motor, edelbrock 600. Will drive today, not in OD and see how she does. Thanks, Jack
The components do not match The biggest culprits apparent right now are the OD Trans and 3.0 gears. There may be more like. cam, converter rpm ranges etc. With a 3.0 rear gear your engine and trans thinks it sees a much heavier weight to move Especially in 1 2 3rd gear. You've taken the mechanical advantage away by the numberically lower gears. Its working harder & This lets you see mpg that reflect pulling that weight. Then in OD you compound the problem by reducing the RPM below optimal range. Now the speedo off and mpg calculation needs some thought.
Interesting - according to Ford literature for 1987, stick shift cars came standard with 2.73 and had an optional 3.08, while all automatics had a 3.27 gear. Engine 5.0L (302cid) OHC V8 (iron block- 2 Valve Heads sequential fuel injection Displacement 302 cid Horsepower 225 @ 4000 Torque 300 @ 3000 Compression 9.5.1 to 1 Fuel Premium (91+ octane) Exhaust aluminumized steel. LX models featured chrome tips Transmission 5 speed T-5 or 4 speed automatice AOD Final drive ratio 2.76:1 , 3.08:1 (Optional), 3.27:1 (automatic)
yup.. they didn't come with much gear. maybe to boost the mpg numbers or something. i also had a 90 years ago that also had a 3.73 gear and that one used to get over 25 mpg. not sure why this 87 doesn't get that much. rumor is that the 87 had a hotter cam, but the 90 has mass air instead of the speed density like the 87. not sure if either of those are the difference.. i'll tell ya though. 2.73 gear and the aod is awesome in the highway. 80mph at under 2500 rpm..
The 351 should have enough torque to pull that (if you build the motor that way) as a OT Jag XJS I had with a LT1/4L60E did fine if not being a hard accelerating car. I knocked down low to mid 20s mpg. That is the downside to the Jag rear; almost everything they built in the 80s had 2.88 gears. And because Jag used a weird ring gear and carrier, you can't swap only gears. But you can install Dana 44 gears and carriers into them by mixing and matching bearings.
yeah i'm seriously considering a explorer rear. i'd love to do the full jag set up but with the truck being built to be my daily and it may do some light towing/hauling i just don't think the 2.88s would be optimal. so with that theory i started looking around today. i did find a late 70s v12 jag unit which could fairly commonly be 3.53 an hour or so away but no response from the seller on ratio. seller wants $225. then theres a 96 t bird irs that should have 3.08 in it an hour or so away for $100. then theres the other option of keeping it solid axle and with that theory i started calling local yards looking for an explorer disc 8.8. most were asking $300+. the pullapart in charlotte has 15-20 and they are $135 but its an hour away and saturdays are my only possible day to even attempt that. Then i found a localish yard that has one from a '98 donor with 90k miles with 3.55 gears for $200. it's getting tempting to just use the explorer and us the focus i was going to put in the irs elsewhere.....
I was in the pick a part checking out an 88 lincoln town car 302, Aod with 3.08 gears in the rear end. Next to it was a 91 Thundebird coupe 302, Aod and it also had 3.08 gears in the rear. The 8 teeth different between a 3.00 and a 3.08 is vertually nothing. So if they both come stock from Ford with those of ratios I personally don't see that 3.00's would make that big of a difference with the Aod tranny. But in all fairness I have very little experience with Ford Aod trannies. However I have run 3.00 with a 700R4 / 350 SBC setup with no issues.
Before I got crazy with the gears, I'd make sure the odometer is right, (free and easy, check with GPS or mile markers) if that is good, take it for a ride with OD locked out, just for a comparison, (bet it won't make 2 MPG difference) then start looking at your engine tune, timing, vacuum leaks, etc. That is all pretty cheap stuff so it should be done first. When you are sure the engine is right, then you can start fooling with gears. A while back I had a 460 in a Studebaker pick-up, got 12 MPG on the highway with 2.75 gears, thought I had too much gear. I went to 3.50s still got 12 MPG, gave up and enjoyed my 12 MPGs
I work on the premise that optimum RPM range at 60mph is around 2K rpm give or take (1.8K - 2.1k rpm) with the correct ratio rear end to suit your tyres. Keeps engine in power band so it is not labouring unnecessarily. My 35 with 305, 700R, 235:65:15 and 3.54:1 turns 2.2Krpm at 60mph. Gets around 28mpg on the highway
With that 3.0 rearend, your car is geared WAY too high for that AOD. My steel '32 Highboy runs a Vortek 350, 700R4 trans, Ford 8"posi with 3.73 gears and 31" Hoosiers 13" wide. At 70-72 mph, I get an honest 24 mpg around 2100 rpms. Although I seldom get into it, off the line is very strong (and just for fun). MAKE SURE your TV cable is properly adjusted or the trans will say "Bye, bye", soon.
Also don't forget tire diameter plays into the equation. If stock vehicles came with an AOD / 3.00 gear and a 25 inch tall tire, and you are running the same setup with a 29 inch tall tire that may be your issue. 25/29 * 3.00 = 2.59 So running a 29 inch tire with 3.00 gears is like running a 25 inch tire with 2.59 gears. You need to be concerned with the final drive ratio not just the gear ratio. PISTON JAMMERS C.C.
check your oil and see if your dumping gas. something is really wrong here. check all the fittings on your gas lines. fords were never real great on fuel but that is even low for a ford. the worse I ever did was my 428 motor and I got about 16 on the highway.
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