hello i am hopeing someone can help me i have a 71 ford f250 truck i truck pull with it has a 472 makeing some good hp i want to look into a cut 3rd gear i am not shure if ya cut the 3rd gear or buy a new gear? but it is a gear that takes place of the 3rd gear makeing it lower than the stock 3rd gear but i bit higher than 2nd thanxs

 

It would be easier to change axle ratio and go a step deeper to "lower" 3rd as it will also improve traction a bit from less chassis and driveline wrap up too.

 

well i have thought about that but i run 4;10's already and 2nd gear works great most of the time but on a losser track i could use a higher gear but i never know the track conditions till i get there also i run a devorced transfercase

 

What size tire?

Its easiest to get different sized tires for different track conditions. A smaller diamater all terrain tire that will let you pull thrid gear would be easier than changing gears. Then you could run your standard tire for second gear pulls on the grippy tracks.

Also what transfercase are you running? Based on the year I'm going to guess its a NP-205? If thats the case you might want to look in to getting a transfercase with a lower low range. That will put the gears closer together so if you stalled out in 3rd gear you would probably be able to pull it now. But then it might also mess up your second gear ratio.

I think the BEST way to go would be to get a gear splitter that can be used in 4 wheel drive. That way you could start off in 2nd over, and than if you start to lug down you can put it in 2nd direct while still under full throttle without stopping

 

If I had a pulling truck, I would be runing at least 4.56's or 4.88's in it or deeper still because I do not call a 4.10 a serious pulling gear. You will also get better traction and less wheel hop with deeper axle ratios because of less driveline wrapup and axle twist for input torque. Check out link below

Click Here

 

Yea if you are looking for more kick in the *** traction. You need 4.56's at least before you look into cutting a gear or getting the splitters. If you are going to get serious you need to get a tractor trans that has the built in splitter. I cant rememeber the model but I do know that the tractors used on cran berry harvest have them.

 

Its overall gear ratio that wins pulls, not axle ratio. Between the transmission gear ratio, transfercase low range ratio, axle ratio and tire diamater there is a "perfect" overall ratio for the most ammount of wheel speed. If the overall gearing is too low all you get is a redlining engine with little wheelspeed. If its too high you will stall the engine out when the sled starts weighting down on the truck. If its really too high you will not even be able to break the tires loose.
That "perfect" gear ratio might only get th etires spinning 1/10th of a MPH faster, but that can make the difference in winning a pull or not.

Also You will not get any better traction with lower gears. Traction, or the ammount of bite th etires get comes from 2 things. First is weight, but since most pullers are all weighed and put in to weight classes, its pretty even between all th etrucks. The second thing that gets you that bite in the dirt is the wheel speed. The faster you get the tires spinning the faster and farther you can get the sled down the track. Sometimes too much wheelspeed will cause you to hop, but thats only if you get in to the throttle too quickly. Youhave to ease into it, and if you feel anything starting to hop let up on the gas a very small ammount to get it to quit hopping, then go back to putting the gas down. If everything goes good you should have it to the floor by the time your 30 feet out, with the engine at its redline and all 4 tires spinning.

 

You are only partally correct here. While over all ratio is important (and BTW, I "pulled" trucks in the 70's and early 80's) deep axle ratios rule in traction and controling wheel hop. Take to identical trucks, one with 4.10 and one wih 5.13's and use trannies to make up the overall effective difference and the 5.13 will rule the day. Ignorance of the physics involved does not change their impact or outcome. WHen you use tall gear with a compound tranny several things happen that effect traction and performance. The engine/tranny combo has to twist/deflect the frame a lot harder to get the same tractive effort on ground as driveshaft takes more torque to twist, Next is the driveline/driveshafts themselves which will wind up some (like a spring) under higher torque loads and they add to wheel hop when it happens because the "spring/wrapup" in the driveline will load and unload and sometime violently and this "whipping" can lead to driveshaft, tranny or axle failure. Then there is the resultant axle housing twist on two axis from input torque. The first is the tendance to try to lift RR and LF tire off ground in responce to driveshaft torque. Just because it is not airborne does not mean that it is not seeing a loss of effective weight on it because of torque input as it MUST react. (Newton's Law) Then there is the tendancy for the axle house to windup in rear suspension parrallel to axle shaft as they try to spin tires and transfer force to ground (you whant traction bars or some extra leafs in springs to help with this but you need a deeper axle ratio for the other problem. It is a wicked cycle as the axle loads and unloads as traction changes and deeper gears will help with everything else except the last item, (axle twist in springs as mentioned above) and make smoother and better power transfers to ground and better pulls at any give wheel speed because of more balanced traction. Again ingoring the forces of physics here in no way changes their impact. ( this is one reason why dozer, loaders and and tractors have such deep final drive to limit driveline torques effect on performance otherwise they would just use compound trannies with taller axle ratios. I can get as scientific about this as you want but I am trying to keep it simple.

 

The last I new you couldn't get the 3rd gears for the Ford trannies. Since you have a divorced transfer case you could put a chevy tranny in it. The chevy guys around here use one with 4.10's that makes them geared close to the same as I am with a NP435 and 4.10's in 2nd. You can get a three speed kit for the chevy tranny and have three gears to chose from. Pro-Fab Machine makes this stuff and they make a tranfer case kit for the 205 that makes them almost unbreakable for a street tire class.

 

Snoman stick to something you actually know like trolling on other forums. So far you have done everything better than everyone else and are so much smarter on physics appearently you must have won the noble prize for physics in the 70s and 80s too and you paper must have been on the physics of frame twist. First off it will not ever try to lift the RR tire off the ground, go watch a race video and you will see the right side of the car squat not lift, left front yes not right rear so once again your showing ignorance. And next deeper gears will make the vehicle much more prone to spinning not the other way around, take a vehicle with 3.50 gears and go try and spin the tires then take the same vehicle and put a set of 4.56 gears in it and see which one spins the tires more and farther. Any jr high idiot can tell you the answer to that one. Next go look at a pro puller they DO NOT change rearend gear ratios for different tracks or track conditions they have drop boxes with changeable gear ratios in the tcase to get the final gear ratio they need to do the best job of pulling.
Next any idiot can tell you axle strength is a major player in pulliing, and the lower gear ratio you go (higher numerical number) the weaker the ring and pinion are. So if you can get the final drive ratio you need without going stupid with the ring and pinion you have a stronger setup.
And I will give you one point although once again any idiot could have come up with it and that is anything you can do to reduce axle wrap is a good thing so stronger or more leafs, traction bars or best of all solid with no suspension at all is best.
And lastly don't try to baffle us with BS cause everyone on here has seen your "getting scientific" and you just look like someone that has maybe read a couple of books but has not one iota of common sense or how things work in the real world, and I am not convinced you have any real learning at all from what I have seen and read from you.
I really don't understand why you keep this stuff up when you get blasted out of hte water with the truth every time you try and baffle people on here with your brilliance.


Actually instead of replying to this I need to post something slightly different
TROLL ALERT

 

Yea, I just caught this and thought "cripes, now he was a truck puller 'back in the day' too"? Next we'll hear he was on the Apollo mission as well

 

No but I bet he designed the space shuttle.

 

i think he just has a lot of midlife crisis'. every decade he changes his profession and extreme sports. when did he have all the time to do all the fun stuff when he was in school learning all this physics mumbo jumbo...

 

I'm not "partially correct", I am 100% correct. I have enoufgh experience in pulling with stock trucks, modified stocks, and pro-modifieds that I wouldn't even take advice from anyone else on how to do it. I think I have just about lost count now, but I can say for sure the number of pulls I have done is up in to the the 4 digit numbers by now. Everything you said here has nothing to do with truck pulling. Axle ratios do not have even a slight thing to do with wheel hop...nothing. You don't know anything about gear ratios or axles and how they work with pulling in stock class trucks. Some of your information is completly wrong too. You can put all the scientific numbers you want in to it and you still won't be able to make it add up right. Also dozers, tractors and whatever has nothing to do with truck pulling either.

 

Bu bu bu bu but he's done the math Dave . . . and he used to truck pull with a snow blower back in the 70's . . . the numbers NEVER lie! His background in aviation/snowplowing/truck pulling/rocket wiring/drag racing/goat milking and all around handyman make him qualified to tell you how to do it right.

Here's a thread with some good info on pulling ratios, pay special attention to greenhighboy's posts about the final ratio: https://www.ford-trucks.com/forums/s...d.php?t=455921