New gear ratio

[Tom'sRedwood38GK]

Well I have changed up the gear ratio on our 1999 Volvo 610, Detroit D60 12.7, Eaton 10 speed Manual Trans..   This truck was built with a 3.70 ratio and at 65 MPH it ran at 1500-1600 RPM. The GearmasterII in the truck showed the engine running at way above the mileage sweet zone.  I wanted to lower the RPM range to around 1300 at 65 to not only keep from pushing the motor hard but also be able to not be a traffic hazard on the higher speed limit roads we encounter since the 55 MPH federal laws changed. I replaced the gear ratio with a 3.25 ratio and all I can say is, it has been a perfect choice from my initial drive tonight .  At 65 the truck is running at 1325 RPM.  I am hoping to not only add longevity but get better mileage running at the best RPM for engine efficiency cruising at HWY speed.  Has anyone else done this to an older truck and what were your results so I can understand more what to expect?    

Since i didn't have to spend a lot on the truck initially  I have done some things to it to bring the truck up to higher standards since it is 19 years old.  A rebuilt air compressor, governor, Air dryer, air junction boxes other air fittings, Shocks, all fluids flushed and changed out to have a flat line for my future. The best part is I am still under budget of what I planned to spend and tens of thousands less than a new to me pickup that could handle our 17,000 pound Redwood 5er.. Also is there any other preventative maintenance I may have missed?  

Thanks in advance for any suggestion anyone may have that i may not know about........

Tom

[ARGO]

I went from 3.73's to 3.23's. Just a little too far I guess, but I can hit anywhere between 55 & 65 in 9th (Autoshift  .74 OD/22.5).  It can supposedly do 97 now, but the great thing is passing a semi at 65 & hitting 10th as you pass...................

[Imurphy907]

I take it you had the computer updated for the new rear end ratio?

I have been thinking about regearing myself. But would also like to add a locker at the same time.

[RandyA]

I'm curious as to how you changed ratios.  I am now single axle having removed the center axle and keeping the rear.  I see two options for a ratio change on my truck - get a complete rear axle with the 3.32 or similar meaning no "set up" of the gears in the rear axle will be needed or getting just the "pumpkin" with the lower numeric ratio, pulling the axles to install it and having it professionally adjusted.  Just thinking to myself all of a sudden (nice to do occasionally) maybe the pumpkin being an integral piece does not need to be adjusted as a separate ring and pinion gear set does?   Anyway, which way did you accomplish the ratio change?  Also, was this a DIY project or did you have it professionally done?

[RandyA]

11 minutes ago, Imurphy907 said:

I take it you had the computer updated for the new rear end ratio?

I have been thinking about regearing myself. But would also like to add a locker at the same time.

On a manual would one need to reprogram the EECM?  Thinking that would only be necessary on an autoshift or automatic.

[Phil D]

49 minutes ago, RandyA said:

On a manual would one need to reprogram the EECM?  Thinking that would only be necessary on an autoshift or automatic.

Reprogramming of the ECM is necessary to keep all functions that are dependent on calculated road speed (speedometer/odometer/cruise/fuel economy display, etc.) working normally and reasonably accurately.

No gear setup should be required when pulling the axles and exchanging the carrier as a complete unit. The "setup" doesn't change as long as none of the internal components are adjusted or removed from the carrier. 

[beemergary]

I just drive my old Cat at 60-65 mph. Would I wish I could run at 1450 rpm's (max torque and hp and where the Cat purr's) yes but will just have to do 1700-1750 rpm's. I would have to change two rear ends and only the speedometer adapter. Too much $$$ knowing it was run more than likely at least 60-65 mph. most of its 1,000,000 miles. I only put 2k-3k a yr. on the ol girl.

[OU812]

This is a LONG shot....but..... could you make transmission adjustment / change to a over drive to get the higher gear and RPM down.  A lot of people look at a truck, and never think about what it was built for.  Over the road truck is set up different the a then say local delivery or logging truck.  I don't know your set up.....but you could spend a few  $$$$ to get the way you want.......or start over on another truck like a lot of us have done.  good luck  OU812

[Tom'sRedwood38GK]

OK, here are answers to some of the questions or thoughts asked and conveyed.  Changing the ratio is what I would call a plug and play set up.  It is the front portion (pumpkin) swap out of the rear axle the pumpkin part is custom geared and pre-adjusted with a core charge refundable at the return of your old pumpkin.  Pull the axles out 6 inches, drop the drive line, unbolt and drop the old pumpkin clean up the old seal material and lay a new bead of black silicone for gasket. And reverse the process.  Since my truck was singled I only needed to do it to one axle.  Also because it is a manual transmission it is a simple process I didn't have to worry about the computer being done at the same time.  The speedometer is off on the truck is 6 MPH slow so at 55 on the truck it is 61 on my GPS. 

This truck is my retirement space for the next 7-10 years so I am willing to put a little more money into it, to make it exactly what I need for my situation.  As far doing the work myself?  I gave a father and son a couple of hundred bucks to do it for me since I am working everyday they provided me a loner car to drive for the weekend.  If you have the place and tools you can do this for around 1500-1600 bucks add 100-200 bucks if you change out the rear end fluid at the same time.  I had already changed mine out and reused to oil I just replaced.  That oil is pretty expensive unless you can find a place that can sell it by the amount you need because it only comes in the smallest quantity 5 gallon buckets at 189.00 bucks. Our truck was taken out of commercial service way back in 2005 at 475,000 miles. I bought it with 598,900 miles on it and now have 603,000 miles.  

Today the computer perimeters are gong to be changed to match the transmission output, rear end and tire size. Since this is a Gen 1 truck it took a while to find a place that can make the changes because the truck is almost 19 years old and the old software is becoming limited availability. 

My total cost of this project has been 1800 bucks whether this has been a cost effective decision only time will tell  and hopefully on the long term will repay it self in a number of areas of savings, wear and tear on the motor and hopefully fuel cost.  For sure the truck likes it now!!  When I set the cruise at 65 it just purrs like big old fat and happy cat.  My thought when I did this was to not ever be in a race to get anywhere but also not be a hindrance on the road.  I feel that towing the max speed should be around 55 to 65 anything more you just beat up the house to much and the safety factor on the trailer tire ratings for towing is usually 65 max.

Edited May 23, 2018 by TomNGina

[Parrformance]

What range gear ratio is best?

[beemergary]

15 hours ago, Parrformance said:

What range gear ratio is best?

 

Depends on tire size and final transmission ratio. If you got the power lower rpm's are better. My old Cat makes the most torque and hp at 1450 rpm's  and it purrs and runs quieter at thet rpm but it was ordered to pull and thus the 3.90 gears. Trucks today make big power (torque) and run at lower rpm's to save fuel and make money.

[noteven]

 

The nut behind the wheel is responsible for about 80% of the fuel economy. The other half is specs, how much stuff you haul around, how faulty your math is...

My goofy little truck burns all the fuel I put in it seems like...

Edited May 25, 2018 by noteven

[atv_idiot]

57 minutes ago, noteven said:

The nut behind the wheel is responsible for about 80% of the fuel economy.

Do you know how to adjust that nut for better mileage? I think mine was over tightened

[noteven]

21 hours ago, atv_idiot said:

Do you know how to adjust that nut for better mileage? I think mine was over tightened

Yep - spend on stacked tuners, each promising hp increase and better fuel economy, until you are at about 2000 hp. That’s where all the increased fuel economy should have you not needing to stop and remove fuel to prevent a spill if driving with a tailwind.

[atv_idiot]

55 minutes ago, noteven said:

Yep - spend on stacked tuners, each promising hp increase and better fuel economy, until you are at about 2000 hp. That’s where all the increased fuel economy should have you not needing to stop and remove fuel to prevent a spill if driving with a tailwind.

Funny thing.. My truck has more HP and TQ than I will ever need (D16) Its my gearing that's the issue. Since I am still running both axles and they are lockers, it would take a VERY long time to recoup the cost of gearing change in fuel mileage. Majority of the time its my right foot that needs to be retrained
 

 

[Parrformance]

So, what is your axle gear ratio atv_idiot?

My 780 came to me with 3.42, seems like a good balance, and keeps the revs right around the sweet spot when doing 60-65 mph.

Edited May 25, 2018 by Parrformance
more info

[atv_idiot]

12 hours ago, Parrformance said:

So, what is your axle gear ratio atv_idiot?

My 780 came to me with 3.42, seems like a good balance, and keeps the revs right around the sweet spot when doing 60-65 mph.

My truck has 3:55's and I'm at my sweet spot at 1500rpm/68mph. As soon as I hit 1600/70mph my mileage starts dropping and the dash starts telling me to let off the throttle. 
I found out my truck was spec'd for pulling heavy loads in western Canada through the mountains

[Tom'sRedwood38GK]

Took my initial trip 304 miles combination of 55 and 65 MPH roads truck by itself. Burned around 21 gal on primarily river grade to and from the city and through small town driving.  14 MPG verse 12.5 I am very happy so far..  This week time to hook up and head for home, 950 miles will be the true test. If I can get 11-12 on my return towing it will be as expected and couldn't be happier. 

Edited May 27, 2018 by TomNGina

[Pete Kildow]

I think a lot of people look  at changing the gears. When a tire swap can for most. Change the ratio enough to get those RPM's down or up. My old truck set up with this tire.

500 rev/mi, , R197 295/80R22.5

Customer Gearing Input
Intended Cruise Speed 65 mph

Engine Turning 1578-RPMS with the R197 tire that is 500 Rev per mile.

Transmission Top Gear Ratio  1, Eaton, RT-13710B

Low Gear Ratio Gear Down Ratio 14.78

Number Of Gears 1.34

Tire Size Rear 500 rev/mi, , R197 295/80R22.5

Axle Ratio 2.93
 

So if I wanted my RPM's around 1350, I could swap to 2.78 gears. Or just find a tire that has 430 Revs per mile. Both would do it. Tire change or Gears, both will get you there. So many people will not take in account the rounds that tire makes in a mile.

Or I could swap to a Over Drive trans with a 0.87 top gear. Get the R's down 200 RPMS. Plus give me the best of both worlds. IF I were to go with a 13 or 18 Speed. I Can run in Direct 16th gear at slower speed. Or run in Over Drive 18th and run  faster with less RPM's. This is all with a manual trans. The auto's, Gear change or tire change only.

[BlueLghtning]

On 5/21/2018 at 1:25 AM, TomNGina said:

Well I have changed up the gear ratio on our 1999 Volvo 610, Detroit D60 12.7, Eaton 10 speed Manual Trans..   This truck was built with a 3.70 ratio and at 65 MPH it ran at 1500-1600 RPM. The GearmasterII in the truck showed the engine running at way above the mileage sweet zone.  I wanted to lower the RPM range to around 1300 at 65 to not only keep from pushing the motor hard but also be able to not be a traffic hazard on the higher speed limit roads we encounter since the 55 MPH federal laws changed. I replaced the gear ratio with a 3.25 ratio and all I can say is, it has been a perfect choice from my initial drive tonight .  At 65 the truck is running at 1325 RPM.  I am hoping to not only add longevity but get better mileage running at the best RPM for engine efficiency cruising at HWY speed.  Has anyone else done this to an older truck and what were your results so I can understand more what to expect?    

Since i didn't have to spend a lot on the truck initially  I have done some things to it to bring the truck up to higher standards since it is 19 years old.  A rebuilt air compressor, governor, Air dryer, air junction boxes other air fittings, Shocks, all fluids flushed and changed out to have a flat line for my future. The best part is I am still under budget of what I planned to spend and tens of thousands less than a new to me pickup that could handle our 17,000 pound Redwood 5er.. Also is there any other preventative maintenance I may have missed?  

Thanks in advance for any suggestion anyone may have that i may not know about........

Tom

Do you find the Detroit 12.7 still has power to pull down at 1300 with the trailer on?  What is yours rated at? My 2000 has a 12.7 rated at 435hp and I think 1650/tq with a 10spd manual and 3.58 rear end with a .74 OD. When I first got the truck it was running low pro 22.5's on the rear. The Detroit seems really happy around 1400-1500 RPM's and even up to 1600 it seemed like the motor didn't mind that at all. I recently changed to 11R 22.5 tires and that made more a change than I expected. It lowered me a hundred RPM in each gear (or picked up about 2-3mph at each RPM), but negatively it spaced out my gears a bit more too. 

These were my original RPM's/speeds before the tire change.
1275 = 55 mph
1375 = 60 mph 
1475 = 65 mph
1500 = 67 mph
1575 = 70 mph
1600 = 72 mph

Now I think I'm at about 1400 at 65mph and 1500 at 70mph. Of course now my speedometer is off a couple mph, but I have my GPS to go by.  The truck does cruise a bit more relaxed now, but on the other hand, I'm not holding hills as well in 10th gear any more unless I'm really in the RPM's. Maybe with your change it made 9th a bit more usable at higher speeds. 

I am a bit heavier than you and my trailer comes in right at 20k fully loaded. I'm 38k total. 

[Tom'sRedwood38GK]

On 5/29/2018 at 1:03 PM, BlueLghtning said:

Do you find the Detroit 12.7 still has power to pull down at 1300 with the trailer on?  What is yours rated at? My 2000 has a 12.7 rated at 435hp and I think 1650/tq with a 10spd manual and 3.58 rear end with a .74 OD. When I first got the truck it was running low pro 22.5's on the rear. The Detroit seems really happy around 1400-1500 RPM's and even up to 1600 it seemed like the motor didn't mind that at all. I recently changed to 11R 22.5 tires and that made more a change than I expected. It lowered me a hundred RPM in each gear (or picked up about 2-3mph at each RPM), but negatively it spaced out my gears a bit more too. 

These were my original RPM's/speeds before the tire change.
1275 = 55 mph
1375 = 60 mph 
1475 = 65 mph
1500 = 67 mph
1575 = 70 mph
1600 = 72 mph

Now I think I'm at about 1400 at 65mph and 1500 at 70mph. Of course now my speedometer is off a couple mph, but I have my GPS to go by.  The truck does cruise a bit more relaxed now, but on the other hand, I'm not holding hills as well in 10th gear any more unless I'm really in the RPM's. Maybe with your change it made 9th a bit more usable at higher speeds. 

I am a bit heavier than you and my trailer comes in right at 20k fully loaded. I'm 38k total. 

Blue,

I wanted to have the truck run easier at the higher speed limits that we have without running the truck at the higher RPM's, 14,500 at 65 MPH, it was was running before my change up.   Now at 65 MPH the engine is running at 1325 RPM my gross weight is at 35,600 k.  I noticed the truck seems to really like that range and did not have any problem climbing any hill big or small, at 65 it really digs in and gets it done.  Climbing the hill out of the Mississippi Valley at Winona, MN I had to drop to ninth because the truck in front was slowing down to much. Then on I-35 climbing the big hill over the Arbuckles, in OK,  I went up that at 65 never had to think about down shifting in fact I gave it more throttle to see what would happen to find I could climb my speed with no problem. 

I am not an expert but I do believe that the truck really likes this new ratio. I was disappointed a little with the mileage at 9.8 but then I bucked a very bad head wind 30 MPH plus most of the trip from WI to TX. Got into numerous severe thunder storms with 50-60 MPH gusts.  That is where the truck shined though the gusts you could feel when hey hit, most of the time my slowing down to 50 MPH when it got bad, but felt very stable much better than my old 1 ton would have ever done.  Time will tell but over all so far I am happy I made the extra investment around 1900 with the speeodo re calibration at the dealer.  Still being under 27,500 over all total invested so far and pretty much done.  I feel I would not loose anything if I would sell the truck today. But for the long term plan I still believe that I made the right decision in getting this project finished. I feel that the motor being older I am giving it a break in lowering the overall RPM at cruising speed.  If I need to run 70 I can without taxing it at all now but then I do not pull my 5er faster than 65 consistently, knowing the extra stress on it, is not good for it.  Only time will tell but so far so good. I did take it to a Volvo dealer and they reprogrammed the computer perimeter to my new gear ratio and tire size 125.00 bucks. 

About the tire size I am running 295/75R22.5 tires and bought them before I left town with the truck from AZ to TX at the time of purchase the old tires being 10-12 yrs old.  Being new to the HDT group it is still a learning curve about all of the options available when it came to this subject. 

Edited May 31, 2018 by TomNGina

[BlueLghtning]

1 hour ago, TomNGina said:

Blue,

I wanted to have the truck run easier at the higher speed limits that we have without running the truck at the higher RPM's, 14,500 at 65 MPH, it was was running before my change up.   Now at 65 MPH the engine is running at 1325 RPM my gross weight is at 35,600 k.  I noticed the truck seems to really like that range and did not have any problem climbing any hill big or small, at 65 it really digs in and gets it done.  Climbing the hill out of the Mississippi Valley at Winona, MN I had to drop to ninth because the truck in front was slowing down to much. Then on I-35 climbing the big hill over the Arbuckles, in OK,  I went up that at 65 never had to think about down shifting in fact I gave it more throttle to see what would happen to find I could climb my speed with no problem. 

I am not an expert but I do believe that the truck really likes this new ratio. I was disappointed a little with the mileage at 9.8 but then I bucked a very bad head wind 30 MPH plus most of the trip from WI to TX. Got into numerous severe thunder storms with 50-60 MPH gusts.  That is where the truck shined though the gusts you could feel when hey hit, most of the time my slowing down to 50 MPH when it got bad, but felt very stable much better than my old 1 ton would have ever done.  Time will tell but over all so far I am happy I made the extra investment around 1900 with the speeodo re calibration at the dealer.  Still being under 27,500 over all total invested so far and pretty much done.  I feel I would not loose anything if I would sell the truck today. But for the long term plan I still believe that I made the right decision in getting this project finished. I feel that the motor being older I am giving it a break in lowering the overall RPM at cruising speed.  If I need to run 70 I can without taxing it at all now but then I do not pull my 5er faster than 65 consistently, knowing the extra stress on it, is not good for it.  Only time will tell but so far so good. I did take it to a Volvo dealer and they reprogrammed the computer perimeter to my new gear ratio and tire size 125.00 bucks. 

About the tire size I am running 295/75R22.5 tires and bought them before I left town with the truck from AZ to TX at the time of purchase the old tires being 10-12 yrs old.  Being new to the HDT group it is still a learning curve about all of the options available when it came to this subject. 

Okay, I had to look at mine again to see where I'm at. I'm at about 1425 at 65mph with my taller tires and 3.58 gearing, so still about 100rpm higher than you. You may really be in a nice gear range that allows you to run 9th on slower reads and still be pretty good. I still find I'm either running 9th a little higher than I would like or lugging 10th on back roads. You are still getting great fuel mileage. I do think I tend to drive a bit faster and not worry about fuel mileage as much as I did in the beginning. I just enjoy having the large truck that handles our large 5th wheels with ease.  

Thanks for sharing the info. 

 

[Pete Kildow]

On 5/31/2018 at 1:02 PM, BlueLghtning said:

Okay, I had to look at mine again to see where I'm at. I'm at about 1425 at 65mph with my taller tires and 3.58 gearing, so still about 100rpm higher than you. You may really be in a nice gear range that allows you to run 9th on slower reads and still be pretty good. I still find I'm either running 9th a little higher than I would like or lugging 10th on back roads. You are still getting great fuel mileage. I do think I tend to drive a bit faster and not worry about fuel mileage as much as I did in the beginning. I just enjoy having the large truck that handles our large 5th wheels with ease.  

Thanks for sharing the info. 

 

Thats where a 13 or 18 shines. Allowing you to drop half a gear, or go up a half gear. My 2.93 gears and 295/22.5's and direct 10 speed trans. Gives me 70 MPH and engine is ok. But a 18 speed OD would allow me to turn in Direct and do the same. Or go up or down as needed.

My truck being a 1995 was built when the company was running 65 MAX and most times 55. AS it was a factory Single axle built to pull doubles.

Pete

[BlueLghtning]

13 hours ago, Pete Kildow said:

Thats where a 13 or 18 shines. Allowing you to drop half a gear, or go up a half gear. My 2.93 gears and 295/22.5's and direct 10 speed trans. Gives me 70 MPH and engine is ok. But a 18 speed OD would allow me to turn in Direct and do the same. Or go up or down as needed.

My truck being a 1995 was built when the company was running 65 MAX and most times 55. AS it was a factory Single axle built to pull doubles.

Pete

Yep, I would love a 13/18, especially  for climbs and descents. There are lots of times where that half gear would be nice. 

[Hewhoknowslittle]

43 minutes ago, BlueLghtning said:

Yep, I would love a 13/18, especially  for climbs and descents. There are lots of times where that half gear would be nice. 

Dan,

You would love a auto shift, I thought I never wanted one till I got one, no looking back.
And 560hp with 1850 torque doesn't hurt the power eather.

Roger 

Edited June 3, 2018 by Hewhoknowslittle