I have recentely started getting into gear ratios and what not. My question is my 3.08 gear ratio came stock. If I were too jump up to a 3.73ls would I notice alot more power, or should I do 4.10ls for a big leap in power. Also if i were to go with one of these gear ratios, do I lose top speed? Thanks

 

You almost certainly will not lose top speed, because your engine cannot reach its power peak in top gear w/ the stock gearing. You may actually get a big increase in top speed (once you overcome your computer's speed limiter witha chip).

Either of those ratios will make a huge improvement in acceleration over the 3.08.

 

split- the gear change that you described will be very noticeable. 3.08 to 4.10 should make your truck have a whole new attitude. In general terms (not considering speed or rev limiters), the lower gears (higher number) will lower top speed, increase quickness, and cause increase rpms on the highway. Your trans gearing has plenty of top end for either gears. My opinion only. What are your goals in the gear change?

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2000 F-150 XL,RC,LB,5.4,4R70W,3.55LS,
Class III tow/Payload #3/Convenience pkgs.,
4-wheel disc/ABS,Chestnut/Parchment 40/60,
Ford bedliner & gas/wheel/spare locks,
3" cold air box modification, Superchip,
Dynomax ultra-flow welded 3" cat-back,
3" exit Y-pipe, Hellwig rear anti-sway bar.

 

Well what I really want is for my truck to have a whole new attitude how you(max) described how it would change. I want something where I can slam from 5th into 3rd gear on the freeway to either race or whatever. Also I didn't want to lose top speed however i usually don't go over 80. WOuld this be a problem to go to a 4.10LS? How much am I looking at here? Thanks a million guys for the replies.
SpliT
Oh yea real quick. You said my tranny could handle this change. Just so I know what the limit is, what would be the lowest gear ratio I could go without having to get rid of my stock tranny?

[This message has been edited by split (edited 08-06-2000).]

 

split- This type of gear change is not good for top speed freeway racing. It is good for quickness, towing, and quarter mile/off the line/low to medium speeds. It will allow better acceleration up to a certain speed. Your gears will be used up quicker, each at a lower speed than 3.08s. I have had many vehicles with 4.11s/4.27s/4.30s and have still had top speeds between 100-120mph; it depends on trans gearing, usefull engine rpms, tire size, etc. When I said "your trans gearing has plenty of top end for either gear", I did not mean to imply that "your gear change would push your trans to the limit". To clarify, I meant that if you chose 3.73s or 4.10s, you will still be able to have a reasonable top speed. Sorry for the confusion.

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2000 F-150 XL,RC,LB,5.4,4R70W,3.55LS,
Class III tow/Payload #3/Convenience pkgs.,
4-wheel disc/ABS,Chestnut/Parchment 40/60,
Ford bedliner & gas/wheel/spare locks,
3" cold air box modification, Superchip,
Dynomax ultra-flow welded 3" cat-back,
3" exit Y-pipe, Hellwig rear anti-sway bar.

 

Find out the original tire diameter and new Tire diameter. Then RPMS at 55 or just plug any number in there like 2000.
http://members.home.net/mjbobbitt/f150/tirecalc.html

 

split,

On your downshift from 5th to 3rd, what rpm are you running in 3rd right now? Take this times 1.33. This will give you the rpm you would be running with the 4.10s. In essence, instead of shifting to 3rd, you would have to shift to 4th instead. The revs would probably be way high in 3rd at high way speeds. For example, if you are turning about 1700rpms on the interstate in 5th gear with the 3.08 gears, you would be turning about 2263rpms with the 4.10s at the same speed. Taller gears are more for stoplight racing than highway racing, and for towing of course. Gears don't really increase your power, they just get you into and through your engines power range quicker. You maybe better off looking at your options in enhancing enging power to get the punch you are looking for. Intake, exhaust, and chip seem to be the standard bang for the buck bolt-ons for our trucks.

Sven

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2000 F150 XLT 4X4 Off Road 5.4L Reg. Cab
K&N, WMS Velocity Tube, and Gibson Sweptside...

(For now)

 

I had 2.73s in my Z28. Beefed up the HP to around 400. On the highway the car was incredibly quick. I could take new vettes and BMWs. Off the line it was quick, but the new Z28s with the LS1 could hang prety good.

I replaced the 2.73s with 3.73s. Thats a full revolution change. HUGE, I mean HUGE difference in car! I could generate 0-60 times of the low 4 second range. The car was unbelievable and scary off the line. However, I totally lost my highway power and was getting about 10-12 MPG (city). It kills your upper end and gas mileage in a big way!

My Expedition has 3.73s (option) and I've driven other Expeditions with the stock gearing. I could feel a good difference as far as acceleration.

If you are looking for acceleration and about 2 MPG less you should goto about 3.73s. It might change your 0-60 times as much as 1 full second! I think 4.10s might be over kill!

 

From all your replies, I have been giving it some thinking and might probably go with the 3.73LS. I feel that 4.10 is a little overkill and would not want to ruin mpg since i already get bad mpg's anyways. But I appreciate all the input everyone's given me. As far as where to go, who would I go see, a transmission mechanic? Can this be done from a novice(me)?
SpliT

 

It can be done by a novice if your VERY intuitive, have the right tools, and a good book.

I would advise hiring someone who knows what they're doing!!

If you dont set it up right the first time, you could damage or ruin the gears. Secondly, even if you get the gear in, keeping it from whining is another hurdle!

The dealer will charge a LEG and 3 fingers!!
I would take it to a garage who has experience installing rear gears.

When I had my 3.73s installed the guy charged me about $200 or so. They ended up whining on the highway, BAD! So I had to have them set up again by another guy for another $300 - $400 or so.... UG!

 

Consider wether or not you will be going to real big tires before you rule out the 4.10's if so then you can negate some of the effect of them that way. Other wise the 3.73's are great gears for all around kind of stuff. Thats what I have and find them a very good compromise. But if I was going to get real big tires I would have gone 4.10's so I would still end up around 3.73 *effectivley*. The time to decide is now not later.

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2000 F-250 Super Duty, SuperCab XLT, Oxford white with medium grey cloth captains chairs, 5.4L Triton V8 (260 HP - 345 FP Torque version!), 4R100 4 Speed Automatic Transmission, 4 wheel ABS, Deluxe Aluminum Wheels, Trailer Towing Package, Class IV Hitch, Reece load distribution system, Escort Sensor II Electronic Brake controller, Sure Stop towing skirt, "Westin" black powder coated step bars, "White-White" head lamps, Herculiner bed liner, ISSPRO Tranny Temp Guage, Excursion center console, Ford moulded mud gaurds, K&N Air and Oil filter, Amsoil XL7500 5W-30, Air filter minder, Perma Cool 8" (800 CFM) Tranny Cooler Fan (manualy switched, Deflect-a-Sheild Aluminum Dimond plate Tool Box.