Why are my starter bolts coming loose??

[llong66]

Hello all, hope everyone had a Merry Christmas! I went out to start my M1008 tonight and heard the dreaded "bendix gear not fully engaging flywheel" sound
I have one of the big box, life time replacement starters and my first thought was great, number 3 this year. I crawled under and the two main bolts were loose, rear support in place and tight. I tightened them up and all is well with the world again...for now. My question is why are they coming loose? I put the motor in in Oct. and its been doing great. When I replaced the motor I bought new starter bolts. They were tightened to I believe its 35ft/lbs, dont have the manual here but thats what I remember. Is the a problem anyone else has? Maybe some blue lock tight?

Thanks and a safe and Happy New year to all!!

 

[Gripy]

I was going to suggest; either crank them on tighter or lock tight them. Maybe a little bit of both, stick with blue lock tight.

 

[llong66]

Gripy, Thanks, I am worried about going to much tighter and cracking the starter housing, but I think I am going with the blue lock tight.

 

[cucvrus]

I don't think you will have to worry about cracking the starter housing. They are pretty stout. Do the new starter bolts that you have the flange washer built into the head and the hatch marks on the bolt shaft? I am asking because I have seen just plain bolts on starters already. I think if you go under there and tighten them bolts you should first make sure they are M10 1.5 metric bolts and not 3/8" x16 standard. That could explain them not staying tight. The thread is very close and I have seen that also in the past. It is worth a look see.

 

[Recovry4x4]

Kimball Midwest (hdwe supplier) sells starter bolts that are flanged like cucvrus mentioned. They have the knurled section as well. I have a small cache of GM bolt and they do not have the flange on them. The flange makes much more sense to me but not to the GM engineers.

 

[camoyj7]

Does the starter have the front mount?

 

[Westech]

rear support in place and tight.

yes he has a rear support.

 

[Hasdrubal]

Never had to locktite my starter bolts. Buy a set of AC Delco starter bolts #15544950, find them cheap on-line.

 

[Keith_J]

Now yet another thing to check...overhauled the starter in my 1031 in the spring and have been driving it a lot.

 

[llong66]

CUCVRUS, yes, they are the bolt with the "built in" washer and the knurled area, I bought them from the local stealership just to make sure they were correct. I was just really surprised that they had worked loose, the motor my truck came with was a mess in that respect, the starter bolt holes had been heli coiled and would never hold, I finally got creative and "studded" the starter in, it worked but made changing it a bear!

 

[acesneights1]

Use only GM bolts. They are correct hardness. Aftermarket is unknown.
Make sure rear support is on and tight.
Never use ether.
Install a block heater for cold weather.
All these things help but getting rid of that Direct Drive and converting to a gear reduction is probably the best bet. That starter is way to heavy for those chincy little bolts.
When I do a starter replacement, or buy a new 6.x truck..I change the bolts ...My latest acquisition did not even make it home for me to do that.
DO NOT use loctite. If you do end up with broken starter bolt...you will hate life if you used loctite.

 

[Hasdrubal]

getting rid of that Direct Drive and converting to a gear reduction is probably the best bet. That starter is way to heavy for those chincy little bolts.

I disagree with this assertation. I've had my M1009 for 10 years, rebuilt the direct drive 27MT twice now. Never had a problem with bolts, mounting or any aspect of its operation. It was engineered for this application, I like how its built so heavy duty.

This from another member ;The CUCV 27MT starter motor is a heavy-duty part. The reason GM went to the gear reduction was cost savings and thats it. Not because they were better. Heavy copper wound starters cost BUCKS $$$ You can wind on a Direct drive till the batteries suck into a vacuum and not hurt them. Try that with the GR and you will melt it.

And ; starting ability of the 27mt verses the 28mt starter. Given good CCA batteries and cabling, the 27mt WILL turn over the engine MUCH faster than the 28MT will. The advantage to the 28MT will be that it will require LESS amperage to crank over the engine at a given speed, and is much easier on the batteries and cabling. The 27MT starter is heavy, and will wear down a good set of batteries in about 5 long cranks, but it REALLY spins the engine over fast

 

[llong66]

Dbl post, please delete

 

[llong66]

Use only GM bolts. They are correct hardness. Aftermarket is unknown.
Make sure rear support is on and tight.
Never use ether.
Install a block heater for cold weather.
All these things help but getting rid of that Direct Drive and converting to a gear reduction is probably the best bet. That starter is way to heavy for those chincy little bolts.
When I do a starter replacement, or buy a new 6.x truck..I change the bolts ...My latest acquisition did not even make it home for me to do that.
DO NOT use loctite. If you do end up with broken starter bolt...you will hate life if you used loctite.

As I had said, I got GM replacement bolts and have the rear support on and tight,Id never use starting fluid and have a circulating coolant heater. I,however, along with the reasons Hasdrubal mentioned above as well as the original DD starter have served GM products fine for many years do not plan on switching to a GR starter. The weight diff. between the 27MT starter and a regular civi 12 volt DD starter is negligible. If this was a starter weight issue many other GM products would be having this issue. I really dont want to use any kind of thread locker and will just be keeping a close eye on it for now. The truck starts VERY easy so I have to do minimal cranking. Maybe I had not torqued them when I reinstalled the new engine, who knows.

 

[cucvrus]

I just looked at the NOS HMMWV starter bolts that I have. They have a dab of lock tight on the threads and the are standard flange less bolts. They just put a small amount on like the torque converter bolts. They are a once and done bolt by military standards. I also just took a pair of 3/8" bolts out of a M1031 that I purchased from the state. That also had a 12 volt starter on it. It would start but act strangely. This is the second truck in 6 months that the state had a 12 volt starter on.????? I took the starters to the repair shop and had them built in 24 volt starters. They are always nice new AC Delco direct drive starters. But Burnt up.

 

[acesneights1]

I have owned numerous 6.x truck with both DD and Gr. Seen alot more broken bolts on the DD. There is a big difference in weight.
I have a gr in my 1008. Never had an issue.

 

[frank8003]

They have a dab of lock tight on the threads and the are standard flange less bolts. They just put a small amount on like the torque converter bolts. They are a once and done bolt by military standards.

It is now very common on automobiles to be built by machines with "one time" fasteners. They are "all over the place" so to speak. Torque is basic to engineering and all fasteners get torqued originally. That did not not just begin recently. i.e. Reusing starter bolts in a '96 Caprice will lead to broken cracked starter nose failure.


There is different ways of making the fasteners so they remain as fastened as per design. They are all one time use if they have a coating, are out of round on purpose, have special locking serrated fixed washers, etc. The "class" of the thread, of the fastener that was removed must be replaced with same and then there is always the problem of running SAE threads where metric threads were.
Reusing lock washers, Belleville washers, copper gaskets and the like is a no-no although that is quite common.
Un-calibrated torque wrenches and misuse of them is your enemy.
Try to put things back together as per design and save yourself the aggravation.
There is a list of all the non-reusable fasteners on every vehicle to seek out.
My list is at TM 9-2320-361-24-2 WP 0470 00View attachment one time fasteners A.pdf

 

[73m819]

Another issue could be that the starter bolts were OVER tightened at one time, this WILL pull the threads in the block, , now each time the bolts are Retightened, the issue gets a bit worse, which means that NEW bolts will not stay tight WITHOUT help.

 

[whatadeuce]

Hello frank 8003,and this chart you provide is news to me, thank you very much

 

[cucvrus]

I have owned numerous 6.x truck with both DD and Gr. Seen alot more broken bolts on the DD. There is a big difference in weight.
I have a gr in my 1008. Never had an issue.

Have you ever lifted a HMMWV starter? It hangs from the same 2 bolts as the CUCV direct drive with one support bracket also. So I am NOT thinking weight is the issue here. That HMMWV starter weighs 3 times what a direct drive CUCV starter weighs. I think torque and the proper bolts are key to keeping these starters tight and operational. But defiantly replace and torque the bolts every time you remove them. I prefer direct drive starters. I have some direct drive starters on the same trucks for 10 years and never had any problems with them. But another one has a gear reduction starter and it never gives me any problems. So the jury is still out. But I don't think the weight is the issue. Just my opinion.