N875ED 98 #1 Posted October 23, 2019 Has anyone installed a smaller drive pulley on the input to a 5091 transmission to increase ground speed in all gears? I'm not at home this week so I cannot measure the pulley's diameter, but it looks to be around 4"; a 2"pulley would double the output speed. If already done, where did you get the pulley and the slightly smaller drive belt required? Share this post Link to post Share on other sites
The Tuul Crib 7,337 #2 Posted October 23, 2019 IMHO I would stay with the correct size pulley and no smaller than a 4 inch. These gears inside are truly not meant to go any faster than they are designed for. Unless you're just wanting to cut the grass quicker. Besides the faster you go the less seat time you can occur!! 1 Share this post Link to post Share on other sites
Achto 27,769 #3 Posted October 23, 2019 (edited) Are you looking to speed up a worker a little bit or build a hot rod? For a worker, this can be done but I don't think that I would go as drastic as cutting the pulley size in half. May be drop by 1/2" to 1" in diameter and try it. Your talking about customizing so you would have to find a pulley with the correct i.d. and key way and the o.d. that you want. There are many sources for this, I would suggest using a cast pulley not a steel stamped one. With the belt, again you're talking custom so you would have to find a local store that supplies belts and do some trial an error fitment. If you're looking to go hot rod, imagination and $ factor are you're limits. Finding pulley and belt size would be the same as I listed above. Keep in mind these tranny's are tough but they do have they're limitations. The faster you spin them the sooner they are likely to break. I have two tractors that I increased the engine pulley size by 1/2". This made 2nd gear on mine about as fast as 3rd gear on a stock . If you increase the engine pulley you will need to make a new belt guard as the original will no longer fit. Decreasing the tranny pulley size will not effect the belt guard. Here is one source for pulleys. https://www.surpluscenter.com/ Edited October 23, 2019 by Achto Share this post Link to post Share on other sites
wallfish 17,080 #4 Posted October 23, 2019 Also, a 2" pulley on the trans will leave very little surface area on the pulley for the belt to engage it and the belt will more easily slip on the pulley. An idler pulley strategically added near the small pulley can add to the belt contact area with the pulley. Plenty of guys have changed pulleys to speed these up so typically there's not an issue with the trans itself but it does take some customization with some trial and error to have it all work correctly. If you're just looking for a little more speed, adding bigger diameter rear tires can accomplish that too. 3 Share this post Link to post Share on other sites
953 nut 55,778 #5 Posted October 23, 2019 If you replace a pulley with one that is half as large you cut the surface area for belt contact in half. You are likely to have belt slippage and be unhappy with the results. John posted while I was typing. 1 Share this post Link to post Share on other sites
wallfish 17,080 #6 Posted October 23, 2019 8 minutes ago, 953 nut said: John posted while I was typing. Beat ya! 4 Share this post Link to post Share on other sites
cschannuth 3,816 #8 Posted October 23, 2019 I upsized the engine pulley from 2.5” to 3.5” if I remember correctly. I put a Predator my dad bought for a project he never used on a 606 roller I bought cheap. Since I could move the engine around a bit I didn’t need to modify the belt guard much. It increased the top speed to about 8 mph. I use it to push snow in the winter and as a neighborhood cruiser the rest of the year. Other than the Lawn Ranger I got from Denny Clarke this is my favorite. 1 Share this post Link to post Share on other sites
Pullstart 63,096 #9 Posted October 23, 2019 Hey guys... @stevasaurus? I’m on the plowing topic still. You might have to shoot me to get me off it! Is low gear in an 8 speed any tougher than hi gear? What if a pulley swap for a high road gear brought low-third up to where high-second usually is? Would this reduce stress in any manner, or just spin inputs faster for the same output speed? Also, I meant to ask at the plow day.. Did the 953 and 1054 transmissions or other big wheel tractors with gear jammers have any different gear ratios, given the taller tire in the end? Different pulley or anything? I know it’s published that most gears have a mph quota at W.O.T. 1 Share this post Link to post Share on other sites
Achto 27,769 #10 Posted October 23, 2019 15 minutes ago, pullstart said: Is low gear in an 8 speed any tougher than hi gear? What if a pulley swap for a high road gear brought low-third up to where high-second usually is? Would this reduce stress in any manner, or just spin inputs faster for the same output speed? I don't know that low is any tougher than high but I have thought about changing pulley size on a 6 speed my self. About the only time that I use low range is when I'm loading on to a trailer. It would be nice to have all of the gears a little faster for me. If I was running a tiller or mowing heavy grass all of the time, then I may not want this change. Share this post Link to post Share on other sites
stevasaurus 22,866 #11 Posted October 23, 2019 As far as I know, all of the gear ratios in the sundstrand transmissions are the same...ie...the 3 & 4 speeds are the same ratio as the high range of the 6 & 8 speeds. As far as toughness, they are all made of the same metal, but through the years they did make some changes in the number of teeth in the pinions, mushroom gear, the spline of the fork gear shaft and the 2nd / 3rd gear. Most of that was done in the rj58' and early suburbans. The 3 piece 5003 and 5010 transmissions. To me, all changes to what was intended, is do at your own risk. If I made one of my horses mow faster, that would mean less time in the seat, and I would have to carry one of those quart beers. Don't forget, you have to start out in the gear you want to use. Going faster also means starting out faster...which may land you on your back with the horse riding you. 2 2 Share this post Link to post Share on other sites
pfrederi 17,879 #12 Posted October 23, 2019 I tried to speed up my L107 by going to a smaller input pulley. Couldn't shift. The belt guard has to be somewhat close in the back also. 1 Share this post Link to post Share on other sites
wallfish 17,080 #13 Posted October 23, 2019 Speeding up low range to match high range is quite the speed increase to the trans so expect to do about 40 + mph in high range 3rd. Never really used low range on the hot rod built years ago but I don't remember it matching the speed of high except maybe 3rd low got up there. Tractor used 4 different drive pulleys with 2 on a jack shaft to increase speed up to 30+ mph. Doing the math for the gear ratios and pulley sizes with RPM of the pulleys will give you a good idea 2 1 1 Share this post Link to post Share on other sites
oliver2-44 9,865 #14 Posted October 23, 2019 If you speed it up very much you will also need to consider upgrading the steering linkage to match the speed 2 1 Share this post Link to post Share on other sites
953 nut 55,778 #15 Posted October 23, 2019 4 hours ago, pullstart said: Did the 953 and 1054 transmissions or other big wheel tractors with gear jammers have any different gear ratios, given the taller tire in the end? Different pulley or anything? You must be able to steer it and stop it! The input shaft pulley on the 1054/953 is larger than on the units with 12" wheels. Also the GT-14 reduction gear that couples the Hydrogear to the differential is different than the Charger/Electro. 2 Share this post Link to post Share on other sites
Pullstart 63,096 #16 Posted October 23, 2019 Good points indeed. Thanks fellas! Share this post Link to post Share on other sites
N875ED 98 #17 Posted October 24, 2019 Nice discussion, gentlemen. Thanks! Share this post Link to post Share on other sites
