F5RACING Posted December 13, 2012 Report Share Posted December 13, 2012 I recentley broke some pinion teeth on my truck. I am not sure what gear to put back into it. I am running 37's with a 12'' lift on it. Is there some kind of chart or can someone point me in the right direction? Thx. Link to comment Share on other sites More sharing options...
JamesHigdon Posted December 14, 2012 Report Share Posted December 14, 2012 I recentley broke some pinion teeth on my truck. I am not sure what gear to put back into it. I am running 37's with a 12'' lift on it. Is there some kind of chart or can someone point me in the right direction? Thx. Gear Ratio Calc. This page a has a lot of good info. and a plug and play gear ratio calculator but there are also a few others on google. For a diesel truck you can typically get away with a little higher ratio (due to the extra torque) and a gas engine will typically want a lower ratio. Link to comment Share on other sites More sharing options...
HiTech Posted December 14, 2012 Report Share Posted December 14, 2012 around 4.10 area is what most i know have .but depends on what you are useing this truck for .... Link to comment Share on other sites More sharing options...
Ford27 Posted December 14, 2012 Report Share Posted December 14, 2012 12"lift WOW!! I have a 4" lift super duty with 35" and I have 4.11. Its a pretty good range but I had to reprogram it to get some power back. With 37" I would probably go with something like a 4.88. That should put you in the ball park of being close to what the factory had in mind. If you want a little more power and gas milage doesnt matter you could try a 5.13 or 5.29 . Also if it's a 4X4 dont forget the front needs to be changed as well or it will kinda feel like its bucking on you due to the tires turning at different rates. Also on pavement different gear rations are catastrophic on transfer cases Link to comment Share on other sites More sharing options...
F5RACING Posted December 14, 2012 Author Report Share Posted December 14, 2012 Thanks for the info. According to calculator the gear in it is a 6.83. That seems odd to me. 6 splines on pinion and 41 on ring gear. Obviously this has been changed. This truck is 4 wheel drive, but I got a deal because the 4 wheel was not working. I assumed it was switch on dash, but It was not. I changed that and problem still there. No lights on switch, so I assumed it was electrical. Truck is a 2003 GMC 1500 with a 4.8. Any info on this? I dont like elctrical trouble shooting, but seems like thats where it is at. Link to comment Share on other sites More sharing options...
F5RACING Posted December 14, 2012 Author Report Share Posted December 14, 2012 Deleted last post. I cant count it seems. Gears are 5.13's. 8 on pinion and 41 on ring gear. Link to comment Share on other sites More sharing options...
4cylfordz Posted December 16, 2012 Report Share Posted December 16, 2012 First thing to do is check the fuses the next is to put the truck up on 4 jack stands and see if the front driveshaft is spinning when you put it in 4wd if it isn't than the actuator motor on the transfer case is bad (looks like a windshield wiper motor) if it is spinning than the front axle actuator is broken. I think those years of trucks have an front axle actuator like the older k1500s but they may not though so don't hold me to that... Link to comment Share on other sites More sharing options...
jwmbishop Posted December 17, 2012 Report Share Posted December 17, 2012 MAKE SURE BOTH ENDS MATCH! A friend bought a truck long ago and it was lifted - 4wheel drive did not work) - the previous owner had only geared the rear for the big tires as he never used 4wd. My friend got 4 to work and with mismatch gears shredded the fronts and the transfer. Gears to use. What trans, what engine etc - MOST transfer cases are 1:1 in high and 2:1 in low. If transmission is .94:1 in high gear, transfer 1.1 and rear gear is 5.13 - you will be turning about 2100 @ 70. But here is what I would consider the most. To get those 37s rolling you will sap torque before it even makes fwd motion. I would not even consider anything BELOW 5.13 with a 1.1 transmission unless the transmission gives you a deep first (2.92:1 area)! LINK to a calculator that is easier and more detailed than the chart type. The way I would approach driveability in planning whether you can pull it off with XXX.XX:1 ratio is look at 5mph speed in first high range. 750Rpm to be a 5mph is probably the WORST case scenario! Using a 2.84:1 first gear (my 42lre transmission in Jeep which I am familiar with) 37s and 5.13 is 750@6 - going from 0-6 with just clutch will be brutal! 0-5 better 0-4 very easy to get moving. Hit a balance between hiway rpm and first gear "take off" rpm. Turning 600 rpm less at 70 to save 100 a year on fuel is not worth "launching" 0-6 and breaking 400 worth of gears, u-joint etc... Next question - what do you climb with 12" of lift? The curb stops at the local mall are only 6".... just kidding. Link to comment Share on other sites More sharing options...
F5RACING Posted December 20, 2012 Author Report Share Posted December 20, 2012 I have not checked the gears, but it has no lights on switch for 4wheel to even engage. I will be checking this weekend while I put in the new rear gears. Thanks. Crawling, its not even rolling. Lets just say I didnt fully think this through. LOL Link to comment Share on other sites More sharing options...
jwmbishop Posted December 20, 2012 Report Share Posted December 20, 2012 Lets just say I didnt fully think this through. LOL Think? When it comes to our toys? Thats a good one. Link to comment Share on other sites More sharing options...
Alloutpc17 Posted December 27, 2012 Report Share Posted December 27, 2012 4.56 is the gear to have with what u have. Anything over is too much gear for 37 inch tires. The lift height doesnt matter. I had the same set up and put 4.88 gear in and it was a little too much. Link to comment Share on other sites More sharing options...
jwmbishop Posted December 31, 2012 Report Share Posted December 31, 2012 4.56 is the gear to have with what u have. Anything over is too much gear for 37 inch tires. The lift height doesnt matter. I had the same set up and put 4.88 gear in and it was a little too much. Depends on vehicle and use though. And even tire weight comes into play! Using a lghter tire will help the feel. My Pitbulls are the heaviest true 35X12 out there and I hate em for that (but love the way they stick to rocks!!!!!) In a 2011 wrangler rubicon (well built for rocks, fully equipped with gear and for sale incidentally) with 35's and its little "underpowered" 6cylinder, 5.13s even have me wishing I had gone deeper - like 5.36 range! With a V8 and transmission with 2.92 first gears - 4.88 probably IS a bit much. But I was shooting for a very low crawl speed - winch should be faster than vehicle in lo/lo at 1800 rpm - so my final in reduction (4:1 in transfer case) was my main targeted goal! Just one of those things where you play with the math until you get the balance between power and economy with longevity and cost factored in! Power wise in high range - going from 32 inch to 35 and from 4.10 to 5.13 it really feels about the same. Link to comment Share on other sites More sharing options...
F5RACING Posted January 11, 2013 Author Report Share Posted January 11, 2013 thanks for the info/input. I went with 5:13s, mainly cause that's what was in already and research pointed that direction also from the charts. It's been 2 weeks now and still working. So far so good. Now I gotta check out the front to see if those were changed. Never stops Link to comment Share on other sites More sharing options...
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