Casper1988 Posted March 29, 2017 Share Posted March 29, 2017 Hi All, I bought a 1988 R model tri-axle log truck recently with a Prentice 120 loader. Was a down south truck and clean compared to what you find up north here in New England. It has a 2070 Maxi torque 7 speed transmission. two lows and then direct five. Fourth to fifth is amazingly high jump (70mph all day ) I live in hill country and 4th direct is the max as I have delivered some loads already. Third is good but need a split gear between 3 and 4. 5.37 rears I believe, would it be cost prohibitive to put a 13 speed into this truck as I do plan on keeping it because it is rust free. Does it bolt up if a Mack tranny is used? Thanks. Quote Link to comment https://www.bigmacktrucks.com/topic/49341-changing-up-my-transmision-in-my-1988-r-690s/ Share on other sites More sharing options...
alex g Posted March 29, 2017 Share Posted March 29, 2017 You can basically put any trans in you want if you have the right bellhousing. I have a 13 speed eaton/ fuller in mine. You'll probably have to shorten or lengthen driveshaftSent from my SM-J320W8 using Tapatalk Quote Link to comment https://www.bigmacktrucks.com/topic/49341-changing-up-my-transmision-in-my-1988-r-690s/#findComment-365907 Share on other sites More sharing options...
terry Posted March 29, 2017 Share Posted March 29, 2017 With a 13 spd and them rears you might get 55 top end and that is at the top on rpm's. terry Quote Link to comment https://www.bigmacktrucks.com/topic/49341-changing-up-my-transmision-in-my-1988-r-690s/#findComment-365910 Share on other sites More sharing options...
Casper1988 Posted March 30, 2017 Author Share Posted March 30, 2017 Terry, if top end is 55 with that tranny that would be ok. It's having the gearing on the back roads as this is not a highway truck. What might be a preferable transmission that you would consider in my situation. Quote Link to comment https://www.bigmacktrucks.com/topic/49341-changing-up-my-transmision-in-my-1988-r-690s/#findComment-365922 Share on other sites More sharing options...
TeamsterGrrrl Posted March 30, 2017 Share Posted March 30, 2017 It'll work worse with a 13 speed, 'cause the Maxidyne engine was designed for wide ratio transmissions. Unless you have the rare low RPM Maxidyne, upshift at 2100 RPM, downshift at 1200, and you'll do fine. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/49341-changing-up-my-transmision-in-my-1988-r-690s/#findComment-365930 Share on other sites More sharing options...
Timmyb Posted March 30, 2017 Share Posted March 30, 2017 (edited) If your 13sp has a top gear ratio of .73 then I would have a rough guess you could get 100km/h or 60mph at 2050rpm. Give or take 50rpm. Edited March 30, 2017 by Timmyb Quote Link to comment https://www.bigmacktrucks.com/topic/49341-changing-up-my-transmision-in-my-1988-r-690s/#findComment-365931 Share on other sites More sharing options...
luke andres Posted March 30, 2017 Share Posted March 30, 2017 i was in the same situation as you i had a t2080 mack tranny 3 lows and 5 highs i had 573 rear gears i went to an eaton 8ll and had to switch my rears to 442 to maintain top speed i like the difference not such a big jump between gear changes i had to shorten driveshaft a couple inches i say go for it its only money Quote Link to comment https://www.bigmacktrucks.com/topic/49341-changing-up-my-transmision-in-my-1988-r-690s/#findComment-365934 Share on other sites More sharing options...
luke andres Posted March 30, 2017 Share Posted March 30, 2017 oh yeah my mack is a 91 dm 690s with a 300 em7 Quote Link to comment https://www.bigmacktrucks.com/topic/49341-changing-up-my-transmision-in-my-1988-r-690s/#findComment-365935 Share on other sites More sharing options...
theakerstwo Posted March 30, 2017 Share Posted March 30, 2017 Like already been stated if that is a maxidyne engine thena 13speed will make the engine feel real weak at top RPM. That engine gets its torque at 1200 and with a 13 speed most guys want to get the RPM up as high as they can were there is no torque 1 Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/49341-changing-up-my-transmision-in-my-1988-r-690s/#findComment-365944 Share on other sites More sharing options...
Casper1988 Posted March 30, 2017 Author Share Posted March 30, 2017 My motor is a 300L, I do believe this to be the low rpm motor say 1800rpm's. Still learning about this truck, thanks for the responses. Quote Link to comment https://www.bigmacktrucks.com/topic/49341-changing-up-my-transmision-in-my-1988-r-690s/#findComment-365957 Share on other sites More sharing options...
GreenGiant2 Posted March 30, 2017 Share Posted March 30, 2017 i have a 300L with a 2080 trans. bid jump between 4 to 5. not good on hills Quote We the unwilling, Lead by the unqualified, are doing the impossible, for the ungrateful. Link to comment https://www.bigmacktrucks.com/topic/49341-changing-up-my-transmision-in-my-1988-r-690s/#findComment-366001 Share on other sites More sharing options...
terry Posted March 30, 2017 Share Posted March 30, 2017 22 hours ago, Casper1988 said: Terry, if top end is 55 with that tranny that would be ok. It's having the gearing on the back roads as this is not a highway truck. What might be a preferable transmission that you would consider in my situation. Was you thinking a mack or fuller 13 spd? The mack is a triple countershaft , will take the lugging torque alot better than a twin countershaft fuller trans. terry 1 Quote Link to comment https://www.bigmacktrucks.com/topic/49341-changing-up-my-transmision-in-my-1988-r-690s/#findComment-366015 Share on other sites More sharing options...
Timmyb Posted March 30, 2017 Share Posted March 30, 2017 So at 1800rpm with the 13sp and your rears you will get 55mph. Terry was spot on. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/49341-changing-up-my-transmision-in-my-1988-r-690s/#findComment-366016 Share on other sites More sharing options...
Casper1988 Posted March 30, 2017 Author Share Posted March 30, 2017 I was thinking Mack tranny. I will have to find one and try it I guess. Quote Link to comment https://www.bigmacktrucks.com/topic/49341-changing-up-my-transmision-in-my-1988-r-690s/#findComment-366020 Share on other sites More sharing options...
superdog405 Posted March 31, 2017 Share Posted March 31, 2017 Don't know how much you want to get involved , but I have a 7LL fuller an pair of Mack rears at 4:42 in heaver duty cast housings that came out from behind a 300 in my 87 superliner. Trans has pto on it and everything in good shape, came from Montana . 7LL same as 8LL ,just one less gear. And it has the hard to find bell housing on it! Quote Link to comment https://www.bigmacktrucks.com/topic/49341-changing-up-my-transmision-in-my-1988-r-690s/#findComment-366055 Share on other sites More sharing options...
superdog405 Posted March 31, 2017 Share Posted March 31, 2017 And yes , most trans will put you at max of 55 or 60 mph against the pump, had the same set up in a 90' 713 and switched out mack trans for fuller 8LL and 60 was tops with the 5:37 gears. Quote Link to comment https://www.bigmacktrucks.com/topic/49341-changing-up-my-transmision-in-my-1988-r-690s/#findComment-366058 Share on other sites More sharing options...
Casper1988 Posted March 31, 2017 Author Share Posted March 31, 2017 This is the kind of info I was looking for , Thanks all. I am gonna put some miles on it and see what is out there. My buddy has a newer Mack with 8LL in it with a 350 motor. Kinda curious what his rears are now. Third gear is ok for 35 or 40mph loaded, wondering about running the rpms above 1800 for pro longed times. How about getting more out of the pump, any adjustments there. Quote Link to comment https://www.bigmacktrucks.com/topic/49341-changing-up-my-transmision-in-my-1988-r-690s/#findComment-366061 Share on other sites More sharing options...
luke andres Posted April 1, 2017 Share Posted April 1, 2017 i talked to a guy in pennsilvania and he too had a early 90s dm tri axle dump that he switch out a mack 2070 and put in a 13 speed mack he also changed from 573 gears down to 442 he said his guys love driving it now said its like a new truck i went with the eaton 8ll because a its cheaper and b i had one in a parts truck and c it has a lower gear ratio than the 13 speeds mack or eaton hope this helps Quote Link to comment https://www.bigmacktrucks.com/topic/49341-changing-up-my-transmision-in-my-1988-r-690s/#findComment-366102 Share on other sites More sharing options...
6368 Posted April 1, 2017 Share Posted April 1, 2017 Why not go 12spd? 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/49341-changing-up-my-transmision-in-my-1988-r-690s/#findComment-366104 Share on other sites More sharing options...
Casper1988 Posted April 1, 2017 Author Share Posted April 1, 2017 I really need to confirm my rear end ratio, I am new to this truck stuff. Been a logger / slash farmer for a long time but left the trucking part to friends. Logging today requires a truck to load trailers and get the wood utilization % up. Thats why I bought one. Always wanted a Mack anyways. I am really liking working on my truck. I was a mechanic in the Navy so big wrenches are just fine with me. Quote Link to comment https://www.bigmacktrucks.com/topic/49341-changing-up-my-transmision-in-my-1988-r-690s/#findComment-366118 Share on other sites More sharing options...
Casper1988 Posted April 1, 2017 Author Share Posted April 1, 2017 Just got off the phone with my local Mack dealer and he kindly ran the #s on my truck. Turns out the rears are a 502 ratio which should be a little better for top end if I go with a Mack 13 speed. Will this bolt up to my truck and I am thinking the drive shaft will be shorter as the 13 is I assume a longer transmission. Any good sources out there for Mack 13 speeds. Quote Link to comment https://www.bigmacktrucks.com/topic/49341-changing-up-my-transmision-in-my-1988-r-690s/#findComment-366120 Share on other sites More sharing options...
terry Posted April 1, 2017 Share Posted April 1, 2017 Just to make sure you can look on front rear just to left of input shaft there is a flat spot with numbers stamped in or punched dots with the ratio, you never know what has been changed. The drive shaft length might or might not need changed. terry 2 Quote Link to comment https://www.bigmacktrucks.com/topic/49341-changing-up-my-transmision-in-my-1988-r-690s/#findComment-366128 Share on other sites More sharing options...
BGarofalo Posted April 1, 2017 Share Posted April 1, 2017 Don't forget to check where your pto is mounted. If its a rear mount be careful of the trans you buy/use because not all had the provision for it. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/49341-changing-up-my-transmision-in-my-1988-r-690s/#findComment-366135 Share on other sites More sharing options...
luke andres Posted April 2, 2017 Share Posted April 2, 2017 keep in mind too that a 13 speed mack will not have as low of a low gear as the 2070 transmission in my mind a 13 speed is more of a road tractor transmission not sure how much you will be using it in the woods pulling out loads of logs i have a mack book that shows the transmission ratios for all kinds of mack transmissions and yes more than likely you will have to shorten driveshaft and redo your pto setup Quote Link to comment https://www.bigmacktrucks.com/topic/49341-changing-up-my-transmision-in-my-1988-r-690s/#findComment-366179 Share on other sites More sharing options...
Casper1988 Posted April 2, 2017 Author Share Posted April 2, 2017 Yes, I have two low holes and also start in low 2 and switch to direct 1 on the fly which works well. Low one is a creeper for sure. Also nice having that low in reverse is nice to when backing up in tough spots. I guess now I should look at what these transmissions have for gearing and match them up to the 2070. The first 3 on the 2070 are great it's after that a few more in hill country could be used. Lots of good info and it's making me think this out before I spend money. Thanks all. Be nice to see those ratios Luke, anyway to scan and pm me. Quote Link to comment https://www.bigmacktrucks.com/topic/49341-changing-up-my-transmision-in-my-1988-r-690s/#findComment-366185 Share on other sites More sharing options...
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