3.55s to much for me?

[pantera77]

I've been saving up for 3.55s and a trac loc for quite some time now. I've all ready decided for the trac loc just to buy this new one from summit: http://www.summitracing.com/parts/FMS-M-4204-F288/ .

Now my question is how bad are 3.55s for gas mileage. I've read on here and cvn that it really won't hurt it that bad, but I drive 60+ miles a day, of which 90% of is at 60-70 mph. Right now I have 3.08s so I know going one step up to 3.27s is a waste of time and money. I figure 3.55s are the best medium for performance and economy but I don't want to over do it. So it's pretty much either the stock 3.08s or the 3.55s. I'm getting the trac loc either way, mainly just for all the snow we get around here, but since I'm going to be getting that, I figure then would also be the best time for a gear upgrade too. Maybe I should just stop worrying and get what makes me go faster.

[Brown_Muscle]

Trac-loc is definitely a good idea for safety and handling. You will almost certainly notice a drop in highway MPG if you swap to 3.55's, so if this is your daily driver then for economy sake you should probably stay with what you have (be thankful you don't have 2.73's like me) But If your really interested in getting better acceleration and off the line performance then definitely get the 3.55's. They are a good mid-way point, the extremes being 3.73's or 4.10's, and 2.73's or lower. Overall its personal preference in this case, just depends on weather fuel economy is more important or acceleration is. You could always do a full H O swap as well....that helps with both!

OBTW welcome, your car looks very clean and shiny

[monterey1962]

My '88 does 20+ mpg on the highway with 3.55's and a built 302.

[Brown_Muscle]

what fuel milage are you getting right now pantera?

[Lincolnmania]

i get 20+ highway with my ho powered 3.55 geared 89 vic........just slightly lower with my ho powered 3.73 geared 86 town car

[pantera77]

what fuel milage are you getting right now pantera?

Last time I checked, which was a few tanks ago, I got 22. Thats with 2 1/8th mile passes, many WOT runs, a few burnouts and sitting in a few traffic jams.
The only other reason I was going to go with 3.55s was that I know the HOs seem to like them better, so I'd be pretty much all set then whenever I get around to rebuilding mine.

[torquelover]

Everyone I know locally with a Panther or FN10 that has gone with the 3.55s has wished they went with the 3.73s. I went from 2.73s to 3.27s and was satisfied. What kind of driveshaft do you have? Slight chance you'll pick up a vibe with an older steel driveshaft.

If you drive 60-70 MPH, MPGs won't vary too much between the two ratios you're on the fence with. Going 85-120 MPH makes a heck of a bigger difference I have found. Even at those higher speeds, the 2.73s had the engine barely revving.

[pantera77]

Everyone I know locally with a Panther or FN10 that has gone with the 3.55s has wished they went with the 3.73s. I went from 2.73s to 3.27s and was satisfied. What kind of driveshaft do you have? Slight chance you'll pick up a vibe with an older steel driveshaft.

If you drive 60-70 MPH, MPGs won't vary too much between the two ratios you're on the fence with. Going 85-120 MPH makes a heck of a bigger difference I have found. Even at those higher speeds, the 2.73s had the engine barely revving.

Driveshafts an aluminum one but I never go above 75 anyways. 90% of the time I'm doing between 55 and 65 unless the traffics bad which of course it always is.

[CheeseSteakJim]

Higher gear ratios will shine in stop/go.

[1987cp]

Everyone I know locally with a Panther or FN10 that has gone with the 3.55s has wished they went with the 3.73s. I went from 2.73s to 3.27s and was satisfied.

... and I've been planning a 3.73 swap on this exact same car. Then again, I never take the car over 75 or so. :p


That reminds me, I need to ask Thain or someone else knowledgable: You can often find 3.73 Trak-Loks on eBay, but they're almost always out of an Explorer or something and for use with 31-spline axles, and axle upgrades are prohibitively expensive for most of us and unnecessary for essentially all of us. I've gotten the notion that the only difference between a 31-spline centersection and a 28-spline is just the number of splines on the side gears, and that the carrier, spiders, springs, clutches, etc. are all identical. Not that I have the slightest clue where to buy 28-spline Trak Lok side gears (those from an open diff won't work), but is this conjecture correct?

[pantera77]

Well I just checked the gas mileage this tank, 22.3, and that was with mostly regular driving.
I'm still undecided on which route to go. I know I'm buying a trac loc either way so I'd already be half way there, then I'd just need to find someone to do it.

[1987cp]

Sounds like my situtation. After getting a good Trak-Lok in my possession and acquiring two used clutch plates for the 8-clutch upgrade, I realized that between the hassle of getting it in and the expense of the $30-plus install kit (the details of which, pathetically enough, I'm still hazy on), I realized it'd be silly not to throw 3.73s at the car at the same time.

[Blaze86Vic]

I guess I'll be the opposite voice here. Yeah as a fun car, and a tow car, 3.73's are the way to go. But for what my car used to be, a highway cruise and 50+ mile daily driver, I wish I had put the 3.31's in there. I plan on getting another crown Vic in the future for taking long trips, and I'll either put 3.31' of the 3.27's in. City mileage is probably better with the 3.55, but highway mileage is all about keeping the revs down. The 2.73 is the absolute best on the highway, but it's such an extremely low gear that every time you have to get up to accelerate it destroys your mileage.

Though I do consistently get 1-2 MPG better in my Vic, I have never been able to get within 3mpg of my highway record that I made when I had 3.01's (25mpg). But I have gotten up to 22mpg with the 3.55's.

[1987cp]

I guess I'll be the opposite voice here. Yeah as a fun car, and a tow car, 3.73's are the way to go. But for what my car used to be, a highway cruise and 50+ mile daily driver, I wish I had put the 3.31's in there. I plan on getting another crown Vic in the future for taking long trips, and I'll either put 3.31' of the 3.27's in. City mileage is probably better with the 3.55, but highway mileage is all about keeping the revs down. The 2.73 is the absolute best on the highway, but it's such an extremely low gear that every time you have to get up to accelerate it destroys your mileage.

Though I do consistently get 1-2 MPG better in my Vic, I have never been able to get within 3mpg of my highway record that I made when I had 3.01's (25mpg). But I have gotten up to 22mpg with the 3.55's.

How is your experience affected, if at all, by your old automatic having the wide ratio gearset? I guess the Overdrive gear is the same, though First is a bit deeper IIRC.

[zoomie]

The best person around here that i am aware of id chads ring and pinion he has one heck of a rep and his prices arnt bad either. hes located in jamestown.