so looking around a bit, supposedly my car has a 2.73 gear ratio in the rear axle by what the VIN sticker and tag on the rear axle say...... stock '88 cougar 302/aod
how does the ratio i have compare to some of the other ratios (the good one, not so great ratio, the so-so ratio ..... is it like the economy ratio because i can't seem to fathom its the neck breaker ratio
to me so far, i'm loving when i can push 26-30 mpg highway but then again, kinda wish it had just that little bit more get up-n-go :burnout:
Despite the standard output 5.0's measly 150 horsepower and dreadfully limited powerband throughout the rpm range, better gearing will help it, and any vehicle for that matter. My friend had an 89 Grand Marquis. I have an 87 Crown Vic. Mine has 2.73s and that simply is ridiculous for a 4000 lb whale. That 89 seemed to wanna get right up and go, the RPM's in each gear went by quicker with fewer MPH, it clearly had 3.08s or 3.27s....I dont know what options were available in those cars. But it wasnt screaming at highway speed either...thank the AOD's good overdrive for that. At 0.67:1, with even 3.73s youre doing abut 2700 at 80 mph, which isnt too bad. I think 3.27s would be good for you. An even better compromise, and with the stock powerplant, throwing a drag gear like 3.73s or 4.10s wouldn't be worth your time. Something higher like that would be fun if you did the H.O. conversion or something even more powerful, but 3.27s would make it keep up with traffic better and require less out of your right foot just to putt around.
I've been really happy with the 3.55's I have. I think they're a great "all around" gear. Decent gas mileage, great performance, rpm's are kept down. Nice.
I'm with Vinnie, my f150 has 3.55 gears, as does my Sport. Snappy, but not too much so...I can't say on the mileage, as I've never drove mine for more than 20 miles, here and there...
If I was running a little taller tire out back, I'd keep 3.73s a consideration, however.
Get yourself a 3.55 gearset...you'll never regret it. :)
You also have a 7.5 rear, 3.45 gears would be a nice improvement. A plus is there is a sale on a trac loc dif. in the for sale section,that is a good buy.
Thanks for the input....I've tried to learn about this kinda thing but didn't have the time or ambition, altho I have not given up just yet.
As for buying today will have to wait only cause the transmission replacement is first on the list but at least I can decide what I want to get and start looking into the swap hopefully by the end of summer, for a winter project maybe
Basically the car is falling on its face with a high gear ratio in the 300 range. I would use a minimum of 3.45 or a recommended 3.73. Here is a comparison of an 8.8 i just did.
This is the pinion gears side by side 2.73 Versus 3.73 8.8
http://i740.photobucket.com/albums/xx46/proguns/005-4.jpg
Available ratios for the 7.5 DIFF 2.73 3.08 3.27 3.45 3.73 4.11 4.56 5.13
I personally would use a 3.73 Final Ratio The 302 is low on HP and torque and its a heavy car. In my opinion for whatever it is worth a 3.73 is dead nuts.
Available ratios on the 8.8 DIFF
2.73 3.08 3.27 3.31 3.55 3.73 3.90 4.11 4.30 4.56 4.88 5.13 5.71 6.14
My vote is for 3.55 for a daily (had them in my Pig of a 92 Tbird SC and loved them). If its more of a weekend car I would recommend the 3.73s. Anything below that is going to be obnoxious to commute in.
I wonder what 6.14s would be like. I have to imagine you would be into the redline before your pants caught up with you.
Well if he has a 7.5 3.55 is not available. Remember he is OD + LOCKUP. The TC came stock with 3.73 with Auto and it is equivalent to the 5.0 in many ways. That is HP and Torque. The 3.73 was chosen for the auto for its first gear overall ratio. The 5 Speeder came with the 3.55 but the later coupes were 8.8 My recommendation is 3.73 for whatever its worth. But going from a 2.73 to a 3.45 is like night and day. Thanks
The 1/8 mile guys run the 6 series gears 88. I had 5.13 in one of my cars years ago. It was interesting for sure. !!!!!!!!!!!!! No problem pulling the wheels off the GROUND HONEST!!
Here is a photo taken by my brother many many years ago. Look at the left front wheel its off the ground. This car was HEAVY . I pulled the wheel up and my brother snapped the photo. That was 1971. But with an elephant under the hood built by me it was outrageous. Everyone egged me on to pull the wheels off the ground. EVERY DAY And i Obliged WILLINGLY
http://i740.photobucket.com/albums/xx46/proguns/017.jpg
Something to keep in mind when dealing with an 87/88 Automatic TCs is the fact that many owners complained that they were horribly gutless. The fix for that was 4:11 gearing. I've come across a few in the salvage yards with 4:11 gears in them. Too bad those gears turn the TC T5 in a four speed.
NUMBERS
4 speeder 1-1 high gear 3000 RPM 26" TIRE 1.00 forth gear Diff 4.11 = 56.5 MPH
5 SPEEDER in fifth 3000 RPM 26" TIRE .78 FIFTH GEAR DIFF 4.11 = 72.4 MPH
Automatic with .67 High gear if applicable I am going to assume this is correct i do not know.
3000 RPM 26" Tire 3.45 rear axle =100.4 MPH
3000 RPM 26" Tire 3.73 rear axle = 92.9 MPH
MY Camaro with 6 Speeder 6000 RPM Diff 4.11 sixth gear .5 Tire 26"= 225.8 MPH
I hope my math is correct YIKES!!!!!!!!! Thanks
"I personally would use a 3.73 Final Ratio The 302 is low on HP and torque and its a heavy car. In my opinion for whatever it is worth a 3.73 is dead nuts." I just did this to mine and it made a world of difference. The guys at trans shop tried to get me to go 4.11 but I thought it would be to much, now I think it would have been fine. I can drive 70 and not buss the motor at all.
Randynten Not much difference between 3.73 and 4.11 either is ok as far as i am concerned. If you have a 4 SPEEDER 3.55 is about all i can take. Randy when i use the word dead nuts thats GOOD. I did not mean using 3.73 gears was nuts. I hope i did not confuse you or me. Thanks. By the way the most common gear change i do in fords is whatever to 3.73 for autos and 5 speeds. On 6 speeders its 4.56. Most ford guys shy away from the 4.11 for some reason. I presonally like them depending on the final drive in the tranny. Theirs an old saying i use in the shop all the time to my guys. PERFORMANCE IS ALL IN THE GEARS. Thanks
No I was agreeing with you. I went from 2.73 to 3.73 and its night and day difference. Best mod I made so far. I never ran an overdrive before so I was thinking the 4.11 would be to much, if I had it to do over I would have took the 4.11s. By the way, I'm running an aod.
Great Randy that is what i thought. If the aod in fact is .67 in OD then 4.11 would have been a tad better. But nothing wrong with the old TRIED AND TRUE 3.73 Thanks
I put the 345 out there because there plenty and cheap. Being it's still a stock SD. Jump up Hp then he should start looking for a 8.8. My ? would it be worth putting 373 or 411 in a 7.5 , If you can buy an 8.8 already geared. Iv'e built my 7.5 already so it only took time, can he? also it may be getting harder to find an 8.8 from a tc soon.
Actually the 7.5 is not that WEAK. They can handle a modded 302 fairly well. The axles are the same as the 8.8 and if the HP is under 350 +or -
they do last if set up correctly. With an auto 350 HP is not a problem for a 7.5. Naturally an 8.8 is the best but not always necessary. Thanks
I agree about the toughness, Mine held up well, still is in something else now.What I'm getting at right now is how much does he want to spend to set up a 7.5 toward buying an 8.8 that will bolt right up? With the gearing already in place?
Ok then he needs to find an 87-88 auto to get the 3.73 gears. Then either convert to disc or transfer his drums over. Either way he has a lot of work to do and find an exact axle in the JY. Then he is SET. So let him start looking. Thanks
I've got a 3.73 rear (8.80 in the garage (No brakes at all), sitting on jack stands.......tripping me every time I walk by it. LOL.
That's why you shove it in the corner like I did with the 88 XR7 8.8 I just bought:hick:.
I would go with 3.73 gears. I had them with the old standard 5.0 in my car and it really woke it up. I was turning about 2400 rpm at 70 on the highway. Now with the non-lock-up converter I'm running it's more like 2800-2900 rpm at 70....
What I recall reading on here or on the corral, or wherever, was that 1985 and older Trac-Lok 7.5's used an Auburn carrier which was weak, and of course an open diff 7.5 is garbage too. After that year though, 7.5 trac-loks were a Dana unit and are much stronger.
The Trac Loc is a less aggressive, street-friendly limited slip suitable for daily driven vehicles and mild off-road use. This unit uses clutches and is Rebuildable.
Auburn gear High Performance posi for Ford 7.5". The Auburn gear limited slip uses a long-proven cone design to provide traction for performance and off-road applications.
Actually the AUBURN IS STRONGER!!
4.10s here. Had 3.73s with 225/50/16s. I had an extra 8.8, so I rebuilt the posi, added an extra clutch and installed a set of 4.10s. Swapped out the rear and went to 255/50/16s and actually picked up mileage! The reasoning was that I could play with different tire sizes if I went to slicks.
I'm with TOM on gear. My Comet ran 11.9xs with a 289 ,6.00s a 2.78 liberty top-loader in full race trim. When we put it back to street trim, my street gears are 5.43s and 375/50/15 Pro-Tracs.....and NO OVERDRIVE! LOL!
NEVER FEAR THE GEAR! :mullet:
I have 3.73 with a c4, first gear is a joke and if I had OD it would probably be fine. I had several v8 foxes and pretty much all were 2.73, biggest jump I did on those was 3.27 which actually gave me better mpg. Guessing it helped the motor not lug as much.
Add 3.15 and 3.31. These are on newer Fords with 8.8 rears.
3.55s aren't a bad choice if you have a 5-speed but with a AOD 2.40 1st gear automatic, anything less than 3.73s are for sissies... My Lighting pickup has 4.10s from the factory, no way I'd want less gear in it... I recently junked a '93 Aerostar that also had factory 4.10s...
Back before O/D trans were common, 3.25 or 3.50 RAR were the norm on the street(my '64 Galaxie 500 with 390 & three on the tree had 3.50s factory, as does my '69 428 Cobra Jet), even 4.11 & 4.30 without O/D was not uncommon... With a 4.10 & a lockup AOD O/D of .68, the final ratio is 2.79, Hell grandmas '60s/'70s LTD ran 2.75s and no one though of those as having too much gear...
Only possible down side to a deeper gear is you may need to have the drive shaft balanced, as it still spins at the ratio of the rear end...
I have a 88 xr7 that i race at the local track, i know from experience that a 4.10 is too much for a stock cars 3.55 is about right in my opinion, My car gets up and goes from 0-60 takes no time to bury the speedo and the car cuts out at a certain rpm.
This is my moto don't fear the gear lol
Depends on what you're doing. Once you're moving, it depends on how wide your power curve is and what speed you want the most gearing. Would you believe me that with all others being equal, a 6000rpm shift point and an AOD, the 2.73 gears would provide 25% more torque multiplication over 3.73 gears in between 53-73mph? I spent probably dozens of hours trying to come up with a spreadsheet that would tell me these numbers when I was choosing gearing some years ago. The graphs match the numbers in EEC buttstuffyzer so I assume I did the math correctly. My spreadsheet also accurately provides me fuel economy numbers for both city and highway - it was dead on for 2.73, 3.08, and 3.55 gears in my car ;)
A 5000rpm shift point moves this advantage to being between 44-60mph, making 3.73's more useful for the street. Since not many 302's breathe well past 5000 rpms, it makes it easy to decide. If course the huge 37% gearing advantage in first up until these shift points helps pull ahead from a stop, if you have traction.
Like with anything else, you have to plan your parts for your desired outcome. Mine was having a good passing range for those times when you get people going 40-50 in a 60+ zone. The 4r70w changes skewed the numbers a bit so my 3.08s (which are right at the middle of 2.73's and 3.55's gearing wise) that I switched to from 3.55's would actually be better if they were 2.73's for that 2nd gear passing. I didn't like the 3.55's because of the impact on economy and the lack of traction that I had with stock tires, in the middle of summer on summer tires. I figured with future engine ideas, it'd be a better bet anyway.
(http://www.masejoer.com/Images/Thunderbird/5000rpms.png)
(http://www.masejoer.com/Images/Thunderbird/6000rpms.png)
As for stock SO motor, the more mechanical advantage, the better! Go with 3.73's, or if you want to use reliable mechanical parts and have your speedo remain accurate, use 3.27's.
And what're you doing diggin up a thread that died in 2011? :p
and yet a perfect example of a "good thread" to dig up imho.
i learned a lot just now. ive got a gear here made in italy still in the box i have no idea what to do with.
x2. It really got me to thinking about the rear end swap I will be doing in the near future. 7.5 with 2.73 to 8.8 with 3.55. Deeper would be better, but I can't wait to see what the 3.55s will do.
what i know is that i have still yet to find a thread here with a good tutorial on "how" tear down the rear and "set" it correctly.
the shop manual explains in great detail how to measure the play and i have it down to a science but they are not speaking to upgrading ect, just repair / assembly so i suppose i could follow the instruction when i need to.
I did a complete Final drive rebuild and posted it on the LS site. Been doing final drives all my life. You need a lot of specialized tools to do it correctly. The DIY weekend worrier can overhaul a pre-set unit. But a gear change is a horse of a different color!!
Here i am doing very hard unit on the bench. NOTE the home made crush sleeve eliminators. I think i invented that. But who knows!!
Just a few photos of a pinion bearing being shimmed and selected
(http://i28.photobucket.com/albums/c209/tfalconier/adec60e9.jpg)
(http://i28.photobucket.com/albums/c209/tfalconier/d7448d01.jpg)
(http://i28.photobucket.com/albums/c209/tfalconier/25c3416f.jpg)
Here is the home made crush sleeve eliminator i made.
(http://i28.photobucket.com/albums/c209/tfalconier/5f3b886e.jpg)
And the pinion is installed torqued to 135 FT/LBS with the proper drag of 12 INCH/LBS !!! SUCCESS
(http://i740.photobucket.com/albums/xx46/proguns/002-69.jpg)
You can buy solid crush sleeves
NOPE NOT FOR THIS UNIT!!!! And there are many units out there that they are not available for. Basic final drives like popular Ford Chevy yes. But not this one. I made my first sleeve eliminator when crush sleeves showed up many years ago. Try and crush a sleeve on a Chevy 12 BOLT WHEEEE!!!. That is interesting at best. Thanks
Cool