Has anyone changed there gearing from the 14.0:1? Where can we get these? How did it increase your bottom end? What happened to the top end?

Any input?

Thanks

Tom Longo

 

My axle ratio is either a 3.55 or 3.31 on my Automatic. How can I find out which one I have? Which one is considered best for low end, the 3.55 or the 3.31? Can I go even lower or higher to get more low end? Where can I buy these? This is unfamiliar ground for me so any info would be great.

Thanks

Tom

 

3.55 would be better for low end. You need to rebuild the rear end with new gears , and I would go with a 4.10 rear end with a limited slip unit.

You will not be able to rebuild the rear yourself, if you are unfamiliar, so have a speed shop do the work for you.

JH

 

I am familiar but I still insist a speed shop install all my gears.

I'm still on stock 3.55's but my next mod is 4.10 gears. I already installed a Powertrax Lock-Right locker myself about a year ago.

4.10's should be standard on auto 4.2's... really I'd go 4.30 but thats just me if I had auto.

I'm going 4.10 but my convince myself on 4.30's on my 5psd!

 

Right.

The reason 4.10's aren't standard is to keep the factory gas mileage up.

With 4.10's in the mn12 thunderbirds, we have trouble with the factory driveshaft, as it is a two piece unit that likes to vibate. We have to replace the shaft with a one piece high speed balanced unit.

Is this a problem with the f series trucks if you get into steep gears?

JH

 

No... We have a one piece DS. I know first hand in a performance application of one truck handling 4.56 gears.

Alot of the lifted guys run 4.30's or 4.56's on 37" tires and they have no problems either although the bigger tires brings it back down to stock equivelent ratio they still have a big DS angle

 

Any Idea's as to who manufactures the 4.10 gears so I can order them and have them installed?

tom

 

Also,

Our trucks are "one wheel wonders?". I thought ours were already limited slip. I thought all trucks were eigther limited slip or posi? Please let me know because when I order the gears I need to order the limited slip diff If I don't already have it.

Tom

 

I'm unfamiliar with gears... What exactly do 4.10 gears do for you? I've been thinking of doing that myself, but I've never looked into gears before.

 

Joseph,

I'm checking into it right now. I'm finding 4.10 gears for about 250.00. It's very similar to putting smaller diameter rear tires on your truck. Understand that you get more horsepower from your motor the higher the rpm's are right? Well, by putting smaller gears in your truck, your essentially raising it's rpm at an given speed. For example, if while driving 35mph your truck, in any particular gear, is running at 3700 rpms with your stock gears, and you change your gears to the 4.10 gears, this will bring your rpm's up to about 4200rpms. Now doing 35mph at 3700 rpms your truck is putting out, lets say, 152 horsepower. So when you punch it, your truck is punching 152 horsepower until it revs from 3700 rpms til redline, where it will use it's full horsepower.

Now, on the 4.10 gears at 35 mph, your running around 4200 rpms. Now your truck is pushing around 160 horsepower, then when you punch it from there, not only do you have more horsepower immediately, but it will also rev to red line much faster, giving you a more instant power boost.

This is one of the first modifications done by people who drag race and is very inexpensive. The only trade off is when your on the highway in 5th gear. With your old 3.55 gears you may run 2400 rpms doing 65mph, whereas with the 4.10 gears you'll run 2800 rpms doing 65mph, so your gas mileage suffers just a tad on the highway. But you get amazing horsepower and torque by changing to a 4.10.

Now, for any of you tech guys that may be analyzing my figures above and are about to comment, all the rpms and mph's I used were all for example puposes only. I have no idea EXACTLY what the real number would be so back off !

Tom

 

The gear ring and pinion set should run you about 149 if you get the ford racing set (which I recommend). A locking diff will run you about 249, you can reuse yours if you already have factory trac-loc rear end.

A shop will get 300-400 bucks to install and rebuild the rear for you. This is labor alone, no materials. Probably about 200 if you bring the pumpkin to them to setup.

You will also need a different speedometer gear installed to keep your speedometer/odometer accurate.

JH

 

They're doing it right now. the 4.10 pinions and the Auburn Diff. I took it directly to the main guys. Steeda is doing it. They are located in Pompano Florida, right down the street from me. They are charging a total of 710.00 for parts and labor for everything. I'm picking it up in an hour. I'll let you know how the performance is....I'm hoping for some really nice low end and exceptional traction. Anything's better than a one wheeler, especially if I want to take it off road a bit, i don't have to worry so much about getting stuck in the mud.

Anyway, I'll let you guys know what my bang-for-the-buck is in a about an hour.

Tom

 

Ah, expensive but nice.

My truck now rev's much quicker and gets into its power band right away. Still though, it's a V6 so when I punch it from a stop, there still is no throw back torque, but it rev's up much quicker and gets going real quick. Because of the Auburn Differential, I can spin the tires even in a turn....hmmm would have been nice to be able to do that though just for fun, but I think it's impossible now. The drivability of the truck is so much better now because the motor doesn't seem to have to work as hard to get going from a stop light, even if i'm just crusing slow.

It definetely was worth the money. I can't wait to take it off road in the sand and see how good the Auburn performs.

tom

 

No, sorry correction....I mean't that I CAN'T spin the tires !!!!! duh!

Tom

 

Oh yeah, price update...total cost was $910.00.

Tom