Shirehorse
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- Mantua, OH
I recently decided to install an underdrive starter on my 1970 XM813 with a 1988 dated NHC-250 Cummins. I did not have any problems with the original Prestolite direct drive starter, so it was not out of necessity but rather boredom.
I obtained my Underdrive starter from SS Member 74M35A2, and it came promptly a few days later in a 30lb box, much to my FedEx driver's chagrin.
Upon first observations, they are not cheaply made, and fit n' finish are spot on, with no child labor mistakes on the outside of the case and no sharp machining mistakes to rip my body parts off. They're Bosch, made in the good ole' USA in the great state of Ohio. The starter pulls 50 amps less than the original direct drive unit. The unit has baffled drains in both the motor and gearbox housings. It's also very quiet, especially when compared to the giant Prestolite beast that comes in these trucks from Uncle Sam.
They are rated for twenty seconds of continuous cranking with a two minute cool down between crankings. They are also designed to last a guaranteed minimum of 40,000 cycles (That's ten years of usage, with multiple starts a day). They are available in both 12v and 24v.
One of the nice things about this starter that attracted me as well was the soft start feature. Basically, the motor and pinion slowly rotate as the solenoid engages them to help prevent misengagements. Per 74M35A2, a misengagement rate of 1-3% is expected to happen on medium and heavy duty starters due to large tooth sizes, but that I shouldn't experience any for at least 50,000 starts unless the ring gear has burrs on it.
So, after getting the required number of beverages for the task at hand, I set forth with my trusty 15/16 wrench and went about removing the two top studs of the old starter. Use a 3/4 wrench to remove the wires on the big studs, and a 3/8 wrench to get the little guys off. Mark which cables go to which studs for easy installation later on your new starter.
The bottom stud of the starter had an odd 5/8 12 point stud in it, which I guess is akin to a rim lock in the hood, in case some mope wants to run off with your eighty pounds of original direct drive starter. If he can get it out without assistance, he can keep it in my opinion. You'd need to have hands like Shiva to maneuver that thing out of there if you're short like me.
Forgive me, I didn't take any pictures of the installation of the new starter, as I figure you'd be bored and quit reading this thread if you had to look at pictures of each of the three studs. I will say this, put the top rear stud in first, as it will help hold the starter up and even in the pilot hole as you install the other two. Install your cables on each of the corresponding studs like they were on your old starter. I used T for Top, ST for Side Top, and R for Rear because I'm unimaginative.
And, I know this thread wouldn't be worth a hoot if I didn't have a video of the new starter in action. This is the first start of the day, 45 degree temperatures, with four 6TL batteries. It has a mean whine to it that I really enjoy, and almost sounds like a really quiet air starter. It DEFINITELY sounds a lot different than the original Prestolite. Available in HD for your viewing pleasure.
https://youtu.be/1N70wu-oqZc
All in all, great success! WORTH EVERY PENNY.
Number of Beers:
Three Dos Equis
Tools Needed:
15/16 Open Ended Wrench
3/4 Open Ended Wrench
5/8 12 point wrench
3/8 Socket and Ratchet
1/2 drive Extension
1/2 drive Ratchet
15/16 socket 1/2 drive
Rope to lift starter
Enjoy!
~Brian
I obtained my Underdrive starter from SS Member 74M35A2, and it came promptly a few days later in a 30lb box, much to my FedEx driver's chagrin.
Upon first observations, they are not cheaply made, and fit n' finish are spot on, with no child labor mistakes on the outside of the case and no sharp machining mistakes to rip my body parts off. They're Bosch, made in the good ole' USA in the great state of Ohio. The starter pulls 50 amps less than the original direct drive unit. The unit has baffled drains in both the motor and gearbox housings. It's also very quiet, especially when compared to the giant Prestolite beast that comes in these trucks from Uncle Sam.
They are rated for twenty seconds of continuous cranking with a two minute cool down between crankings. They are also designed to last a guaranteed minimum of 40,000 cycles (That's ten years of usage, with multiple starts a day). They are available in both 12v and 24v.
One of the nice things about this starter that attracted me as well was the soft start feature. Basically, the motor and pinion slowly rotate as the solenoid engages them to help prevent misengagements. Per 74M35A2, a misengagement rate of 1-3% is expected to happen on medium and heavy duty starters due to large tooth sizes, but that I shouldn't experience any for at least 50,000 starts unless the ring gear has burrs on it.
So, after getting the required number of beverages for the task at hand, I set forth with my trusty 15/16 wrench and went about removing the two top studs of the old starter. Use a 3/4 wrench to remove the wires on the big studs, and a 3/8 wrench to get the little guys off. Mark which cables go to which studs for easy installation later on your new starter.
The bottom stud of the starter had an odd 5/8 12 point stud in it, which I guess is akin to a rim lock in the hood, in case some mope wants to run off with your eighty pounds of original direct drive starter. If he can get it out without assistance, he can keep it in my opinion. You'd need to have hands like Shiva to maneuver that thing out of there if you're short like me.
Forgive me, I didn't take any pictures of the installation of the new starter, as I figure you'd be bored and quit reading this thread if you had to look at pictures of each of the three studs. I will say this, put the top rear stud in first, as it will help hold the starter up and even in the pilot hole as you install the other two. Install your cables on each of the corresponding studs like they were on your old starter. I used T for Top, ST for Side Top, and R for Rear because I'm unimaginative.
And, I know this thread wouldn't be worth a hoot if I didn't have a video of the new starter in action. This is the first start of the day, 45 degree temperatures, with four 6TL batteries. It has a mean whine to it that I really enjoy, and almost sounds like a really quiet air starter. It DEFINITELY sounds a lot different than the original Prestolite. Available in HD for your viewing pleasure.
https://youtu.be/1N70wu-oqZc
All in all, great success! WORTH EVERY PENNY.
Number of Beers:
Three Dos Equis
Tools Needed:
15/16 Open Ended Wrench
3/4 Open Ended Wrench
5/8 12 point wrench
3/8 Socket and Ratchet
1/2 drive Extension
1/2 drive Ratchet
15/16 socket 1/2 drive
Rope to lift starter
Enjoy!
~Brian
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