ZombieRV
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M109a4 /a3: Reducing rpms, gaining speed / tranny / gearing solution & crowd sourcin
Hello,
If you have an m109 with a Cat 3116 and Alison 1545at:
In regards to going slightly faster, with the main objective of dropping the rpm's, and i am talking about only doing 55 on a mostly flat/mostly straight, major freeway lol... I have read the threads... bloody all of them.
I have spoken to Alison Tranny, Michelin, & Overson.
My solution...
The work & costs involved in trying to swap engines & trannys that Won't fit without major adjustments isn't worth it.
The simplest fix is changing the differential gears in those lovely top-loader Rockwell axles and adding 395 tires.
***Overson said they would be willing to manufacture a custom gearset near the 5.95 range, for the same price of their 4.95 sets... $1,200.00 each, if at least 15 sets are ordered.
That's 5 people ordering 3 sets each, or 8 people ordering 2 sets each. If anyone wants to order let me know. I'm in.
Probikestorage@gmail.com
The stats:
- Drop the short shaft to the rear wheels = 1 less gearset needed, plus slightly less drag. Still leaves a kick arse 4x6.
- 4.95 is too low (rockcrawler ratio) for a 12,000 pound truck. 5.95-ish offers just enough speed increase/reduction of rpm's.
- 395 tires add to the speed increase ratio that matches the 5.95 gear, but also offer a higher weight rating, which when combined with their 55 mph speed rating, it gives a good window of safety to do 60 mph for a brief period if required to pass another vehicle. Run flats help avoid rolling it IF there is a blowout, as the truck only drops approx 4" instead of 8"...plus drive to the nearest shop / no tow needed.
- Alison has no 'tall' or OD gearset for the 1545. Basically nothing else will fit without major modifications due to engine size and bell housings. Most brownie boxes are too big. If a total retrofit is required with welding and frankenstein modifications you could end up with an insurance issue, via the configuration not approved by any Ministry of Transport.
- Would I go 55 on the original 14.5 tires? Heck no. Lower weight/speed rating plus all the blow-outs reported, no thanks.
*Currently my M109 does 56 mph @ 2750 rpm, loaded for camping with 20 gallons of water and a mini atv.
Overson says 5.95 would be 55 mph @ 2390 rpm. 60 mph @ 2608 rpm.
My 109:
- Alison 1545 with Dextron 3 oil (as per Alison).
- 395 tires with run flats (also act as bead-lock safety). Run at 55 psi for highway use to get maximum tire diameter. Fresh tires yield 46" diameter. (55psi for 60psi max rims).
- All tires balanced with "Balancing silica beads"... not pounds of added steel weights. BB's keep the tires balanced at All speeds.
- front lockers (manual). Less drag.
- disconnected rear short-shaft. Less drag.
- no issues with the drum brakes / stops fast enough, but will add front disk eventually.
So if anyone else crazy enough wants to spend $2,400 plus tax to get the revs down... let me know. I figure it's easier then replacing a blown 3116 pos.
Thx
Hello,
If you have an m109 with a Cat 3116 and Alison 1545at:
In regards to going slightly faster, with the main objective of dropping the rpm's, and i am talking about only doing 55 on a mostly flat/mostly straight, major freeway lol... I have read the threads... bloody all of them.
I have spoken to Alison Tranny, Michelin, & Overson.
My solution...
The work & costs involved in trying to swap engines & trannys that Won't fit without major adjustments isn't worth it.
The simplest fix is changing the differential gears in those lovely top-loader Rockwell axles and adding 395 tires.
***Overson said they would be willing to manufacture a custom gearset near the 5.95 range, for the same price of their 4.95 sets... $1,200.00 each, if at least 15 sets are ordered.
That's 5 people ordering 3 sets each, or 8 people ordering 2 sets each. If anyone wants to order let me know. I'm in.
Probikestorage@gmail.com
The stats:
- Drop the short shaft to the rear wheels = 1 less gearset needed, plus slightly less drag. Still leaves a kick arse 4x6.
- 4.95 is too low (rockcrawler ratio) for a 12,000 pound truck. 5.95-ish offers just enough speed increase/reduction of rpm's.
- 395 tires add to the speed increase ratio that matches the 5.95 gear, but also offer a higher weight rating, which when combined with their 55 mph speed rating, it gives a good window of safety to do 60 mph for a brief period if required to pass another vehicle. Run flats help avoid rolling it IF there is a blowout, as the truck only drops approx 4" instead of 8"...plus drive to the nearest shop / no tow needed.
- Alison has no 'tall' or OD gearset for the 1545. Basically nothing else will fit without major modifications due to engine size and bell housings. Most brownie boxes are too big. If a total retrofit is required with welding and frankenstein modifications you could end up with an insurance issue, via the configuration not approved by any Ministry of Transport.
- Would I go 55 on the original 14.5 tires? Heck no. Lower weight/speed rating plus all the blow-outs reported, no thanks.
*Currently my M109 does 56 mph @ 2750 rpm, loaded for camping with 20 gallons of water and a mini atv.
Overson says 5.95 would be 55 mph @ 2390 rpm. 60 mph @ 2608 rpm.
My 109:
- Alison 1545 with Dextron 3 oil (as per Alison).
- 395 tires with run flats (also act as bead-lock safety). Run at 55 psi for highway use to get maximum tire diameter. Fresh tires yield 46" diameter. (55psi for 60psi max rims).
- All tires balanced with "Balancing silica beads"... not pounds of added steel weights. BB's keep the tires balanced at All speeds.
- front lockers (manual). Less drag.
- disconnected rear short-shaft. Less drag.
- no issues with the drum brakes / stops fast enough, but will add front disk eventually.
So if anyone else crazy enough wants to spend $2,400 plus tax to get the revs down... let me know. I figure it's easier then replacing a blown 3116 pos.
Thx
