94 6.5TD

Rolls over slow like one batt is dead, but I tried swapping them out and then tried unhooking one, then the other... tried cleaning all contacts (the only one I haven't done yet is the end on the actual starter) It so far still starts every time, because I can roll it over for a long time and the batts don't slow down any more, but it used to roll over real fast which let it start up much sooner. I am thinking maybe solenoid or starter, but thought maybe someone has had this problem and has some ideas to try before I start dumping money into it. Thanks.

Are they new batteries?

took an almost new batt from my other truck, bought a matching batt and put them in (one new one almost new same model) stuck the other batts in my other truck and they were fine. it also rolls over the same with either battery unhooked which I don't understand. Oh they are 900 ca batts

most likely the starter or the cable going to the starter by what you are describing

Does it roll over slow ALL THE TIME, or is it only after it sits for a little bit.

Since you said you have tried new (or recently charged batteries) I won't suggest checking the voltage on the batteries...

If it is after it sits a little bit... then you may have a parasitic draw... To find that you need to hook up a Multi-Meter that can read Amperage and see if you have any draw. You shouldn't see any more then like 5-10 mA (.005A-.010A).

If it does it all the time....

Check your battery grounds. Each battery has its own ground, if one of the batteries has a bad ground it will not charge properly causing slow cranking.

Check your charging system... make sure that both batteries are getting the same charge, if not... your crossover cable may be bad (which would also cause a slow crank).

If your battery and charging system checks out... the brushes in your starter may be pretty warn... If you think you can handle it you could possibly remove the starter, open it up and put new springs/brushes in it. Would save you a couple hundred bucks as long as your solenoid and armature is fine. I would also check the resistance on your starter cable... make sure it doesn't have any resistance.

I forgot... You can try something to see if the crossover or bad grounds is causing your problem... connect a set of jumper cables to each of the batteries... POS to POS and NEG to NEG. That will see if one of your batteries has a bad ground or you have a bad crossover... you'd have to do more troubleshooting if it starts fine that way. I'm not sure if many people approve of that method but meh lol.

Yeah, I've regrounded both batts and cleaned all of the terminals and cables, it doesn't matter if it sat for days or minutes, and the far battery rolls it over through the positive cable between the batts even with the near batt disconnected so I am pretty sure the problem is after the batts, either the cable to the starter, the solenoid or the starter... it sounds like I don't have a choice but to pull the starter and see if I can find anything. thanks for the info.

Ebay has this starter for $90... says it will fit my truck... does this sound right??

NEW STARTER CHEVROLET GMC DIESEL 6.2 6.5 HIGH TORQUE!
Replaces Part Numbers:
AC DELCO 323-407, 323-447, 336-1912,323-446, 336-1911
DELCO 10465014, 10465054, 10465168, 1113267, 1113270, 1113296,10465013, 10465053, 10465296, 1113266, 1113269, 1113295

OEM(s): Delco, Chevrolet
Starter Family: Delco 28MT
Type: OSGR
Voltage: 12 Volts
Rotation: CW
Teeth/Splines: 10 Teeth/Splines
Pinion/Splines OD: 32mm / 1.260in
DE Housing Number: 371-12104
Mounting Hole 1: 10.3mm ID Unthreaded
Mounting Hole 2: 11.4mm ID Unthreaded
New or Remanufactured: New
Approximate Weight: 17.945 lbs / 8.16 kg

Who sells the starter first off.

Second off, why not have your starter tested on a test bench. Most places test them for free.

Third, find a local rebuild shop to rebuild your current starter if it's bad. Those cheap Ebay starters are garbage. One member here had one stick on since the solenoid welded itself on randomly one day. Local auto electric shops are the way to go i'd say. Most starters and alternators from ebay or most parts stores are made in mexico/china/india/etc and are made with garbage parts.