ARGH! FlexPlate Advice Please...

[FlameRed]

Indeed I am not see much talk about using a gear reduction on a HMMWV.

Questions I see that were asked include:

• Do you use the same shim?
• Will the existing wiring reach?
• Do you need a different front support?

I see they offer it on Amazon and it is returnable. I'm thinking of trying it and having my original rebuilt professionally locally and keep it as a spare.

I need to find the process for shimming these as I have no desire to tear up a brand new flexplate testing this.

 

[87cr250r]

The 28MT starters explicitly state no shim on the housing.

The 28MT is not available in isolated ground as far as I know so you'll need to have a starter sized ground wire attached to your engine block. If you have a ground fault things might get exciting when you ground the block.

Front supports cost few dollars. The 28MT advantage is supposed to be lower purchase cost and better starting ability. Is the cost of the correct support bracket going to offset the lower cost overall?

 

[TOBASH]

HMMWV starters are water tight. That also means that dust and carbon that are generated cannot escape, and eventually clog these units and require rebuilds.

 

[FlameRed]

The 28MT starters explicitly state no shim on the housing.

The 28MT is not available in isolated ground as far as I know so you'll need to have a starter sized ground wire attached to your engine block. If you have a ground fault things might get exciting when you ground the block.

Front supports cost few dollars. The 28MT advantage is supposed to be lower purchase cost and better starting ability. Is the cost of the correct support bracket going to offset the lower cost overall?

Thank you. Reading a bit more, I see a gear reduction starter will have problems without the proper front support bracket. I see GM part number 23502557 might be the correct part for a gear reduction starter on a big block GM engine, 454 gas or 6.2 or 6.5 diesel.

I have to look at the block and see if we have threaded holes might be available to bolt it too as shown here:

Whereas the stock bracket for the original starter seems like it is part of the motor mount.

EDIT: I took my old starter to a local rebuilder and he had a brand new replacement for $800. He is going to rebuild my old one for $300 which I will keep as a spare.

 

[FlameRed]

Bit of an update.

I hoped I could pull the tranny back far enough to R&R the flexplate and avoid dropping the tranny completely but sadly, I could not move it far enough back because the tank and muffler prevented that. So I had to drop the tranny.

I received the gear reduction starter. It is made in China It looks good, but who knows. Here is what I see:

• It is definitively not water tight. It has two drip tubes.
  
• There is a ground terminal
  
• It did not come with a shim kit, or new bolts, or the gauge to measure clearance.
  
• It looks like it is made of all new material.
  
• It does NOT seem to have a bolt or hole for a front support bracket. Just uses the two stock bolts?

So I looked and there are some YouTubes on how to shim a starter. One technique uses a bit to measure the gap between the starter gear shaft and the top of the teeth of the flexplate. Another is to look at how the gears mesh using gear paint like on a diff. And a third is to push out the starter gear and measure the gap between a tooth and the flexplate gear. But what should the gap be?

So I looked at the Technical Service Manuals I have and I am not seeing a procedure to determine the proper shim. On a post above, @87cr250r says not to use any shim. Anyone confirm that or know the proper procedure to determine how to shim a M998 starter so I don't eat up another flexplate / starter gear?

I see two thickness available at HPG - .04" and .08" and my old starter did have a shim, not sure which thickness.

My old starter is being re-manufactured. Still in the shop.

EDIT: I found this post:

You don’t need shims…I’ve installed hundreds of hmmwv starters and about half never had a shim…made no differenc.

Starter Shims
My M998 had no shims in place when I got it either. It finally broke the bendix in half and the starter had to be rebuilt. The corrrect shim is the 0.8 mm. I got mine from Kascar and have not had a problem since. The word shim in this case is a joke it is a spacer. 0.8mm is thick and when not in place the starter is cocked. I belive this is due to the stater being designed for the deuce and five ton and retrofitted to the M998
Tom

 

[jake20]

Bit of an update.

I hoped I could pull the tranny back far enough to R&R the flexplate and avoid dropping the tranny completely but sadly, I could not move it far enough back because the tank and muffler prevented that. So I had to drop the tranny.

I received the gear reduction starter. It is made in China It looks good, but who knows. Here is what I see:

• It is definitively not water tight. It has two drip tubes.
  
• There is a ground terminal
  
• It did not come with a shim kit, or new bolts, or the gauge to measure clearance.
  
• It looks like it is made of all new material.
  
• It does NOT seem to have a bolt or hole for a front support bracket. Just uses the two stock bolts?

View attachment 894579

So I looked and there are some YouTubes on how to shim a starter. One technique uses a bit to measure the gap between the starter gear shaft and the top of the teeth of the flexplate. Another is to look at how the gears mesh using gear paint like on a diff. And a third is to push out the starter gear and measure the gap between a tooth and the flexplate gear. But what should the gap be?

So I looked at the Technical Service Manuals I have and I am not seeing a procedure to determine the proper shim. On a post above, @87cr250r says not to use any shim. Anyone confirm that or know the proper procedure to determine how to shim a M998 starter so I don't eat up another flexplate / starter gear?

I see two thickness available at HPG - .04" and .08" and my old starter did have a shim, not sure which thickness.

My old starter is being re-manufactured. Still in the shop.

EDIT: I found this post:

I would personally throw the starter in, apply voltage to the solenoid, and just manually watch the bendix engage into the flexplate without actually trying to turn it over. I’d do this in a few spots along then flexplate by manually turning the crankshaft over.

This should at least give you an idea of whether it’s meshing too tight, should retract pretty easy.

EDIT: To which if it’s meshing too tight, add a shim at that point and try again.

 

[Mogman]

That starter does not need a front mount, there is not enough weight hanging off of the nose piece to warrant one.
It would be a challenge to just engage the bendix without cranking the motor.
I would start with no shim and have someone activate the starter while you watch to see that the bendix engages and disengages smoothly without actually starting the engine (disconnect the IP) if it does not retract smoothly it is too tight.

 

[jake20]

That starter does not need a front mount, there is not enough weight hanging off of the nose piece to warrant one.
It would be a challenge to just engage the bendix without cranking the motor.
I would start with no shim and have someone activate the starter while you watch to see that the bendix engages and disengages smoothly without actually starting the engine (disconnect the IP) if it does not retract smoothly it is too tight.

My testing consisted of leaving the primary 24V lugs disconnected, and then just kicking the bendix out with a bench top power supply hooked to the solenoid positive. I was pretty paranoid with that being my 3rd starter at that point

 

[FlameRed]

Another update on this gear reduction starter. I decided to give it a try, and keep the rebuilt original as a spare.

Still a PITA to install even though it is less than half the weight of the original. Good news is all the original wiring reached after a bit of fiddling. The only modification I had to do was reroute the lead that come down from the forward upper part of the engine and mounts to the solenoid post.

I did NOT install any spacers. It seemed to start without unusual noises. As the other posters noted, hard to get the gear out and mesh with the flexplate ring gear without it spinning to measure clearance.

Torqued the two bolts to 40 ft/lbs and will let it be for now. Hoping it lasts but if it does not I have the original.

The bad new is after I topped off the tranny fluid, it seemed to develop a leak! Enough for today and I will look at that tomorrow.

 

[FlameRed]

Another update on the gear reduction starter.

Found that the two piece torque converter cover, the part that covers the starter - the holes won't line up with this starter. So I'll have to look at how to solve that.

The starter seems to be working well. Yesterday, I replaced the leaking evaporator and now it has ice cold AC It started flawlessly and seemed to run great while I was charging it with freon. I found that the tranny leak I had was caused by me not seating the dip tube all the way home so that was an easy fix.

Seemed like I was on a roll! Nah!

Today not so much. I am a bit frustrated. I was going to reinstall the dog house, which is always a bit of hassle with that AC under the radio shelf. Before I put the dog house back but I assume while I was fiddling with the dog house I managed to knock off a connector on the sensor on the back of the engine. I saw the connector for the tach sensor at the rear center back of the engine at the top was disconnected - 2 wire plug. I forget what you call this. Plug did not hold in too well. So I zip tied it on.

But now the starter will not crank at all. No click. Nothing except I do get the wait light, and the gauges come to life.

So I gave up for the day since it started raining and my VOM bit the dust too. Once I get a new VOM, I will do the usual tests, protective control box, neutral safety starter switch, yes it was in park, starter switch. Hope it is something simple and repairs stop piling up one on top another!

 

[jake20]

Another update on the gear reduction starter.

Found that the two piece torque converter cover, the part that covers the starter - the holes won't line up with this starter. So I'll have to look at how to solve that.

The starter seems to be working well. Yesterday, I replaced the leaking evaporator and now it has ice cold AC It started flawlessly and seemed to run great while I was charging it with freon. I found that the tranny leak I had was caused by me not seating the dip tube all the way home so that was an easy fix.

Seemed like I was on a roll! Nah!

Today not so much. I am a bit frustrated. I was going to reinstall the dog house, which is always a bit of hassle with that AC under the radio shelf. Before I put the dog house back but I assume while I was fiddling with the dog house I managed to knock off a connector on the back of the engine. I saw the connector for the tach sensor at the rear center back of the engine at the top was disconnected - 2 wire plug. I forget what you call this. Plug did not hold in too well. So I zip tied it on.

But now the starter will not crank at all. No click. Nothing except I do get the wait light, and the gauges come to life.

So I gave up for the day since it started raining and my VOM bit the dust too. Once I get a new VOM, I will do the usual tests, protective control box, neutral safety starter switch, yes it was in park, starter switch. Hope it is something simple and repairs stop piling up one on top another!

Check your actual ignition switch too, I ran through/tested 3 of these before my issues were solved.

My issue was that aftermarket (purchased through both Kascar and Mac) start switches were leaving flea current to the starter in the "run" position, so the bendix was staying engaged on the flexplate while driving around.

Your issue sounds different but definitely check your start switch. HPG has the correct original switches if you need to replace it, anywhere else is a toss-up and risking the starter IMO.

 

[GuntherRommel]

Check your battery ground connections. Make sure they are clean and tight

 

[FlameRed]

Another update on the gear reduction starter.

Found that the two piece torque converter cover, the part that covers the starter - the holes won't line up with this starter. So I'll have to look at how to solve that.

The starter seems to be working well. Yesterday, I replaced the leaking evaporator and now it has ice cold AC It started flawlessly and seemed to run great while I was charging it with freon. I found that the tranny leak I had was caused by me not seating the dip tube all the way home so that was an easy fix.

Seemed like I was on a roll! Nah!

Today not so much. I am a bit frustrated. I was going to reinstall the dog house, which is always a bit of hassle with that AC under the radio shelf. Before I put the dog house back but I assume while I was fiddling with the dog house I managed to knock off a connector on the sensor on the back of the engine. I saw the connector for the tach sensor at the rear center back of the engine at the top was disconnected - 2 wire plug. I forget what you call this. Plug did not hold in too well. So I zip tied it on.

But now the starter will not crank at all. No click. Nothing except I do get the wait light, and the gauges come to life.

So I gave up for the day since it started raining and my VOM bit the dust too. Once I get a new VOM, I will do the usual tests, protective control box, neutral safety starter switch, yes it was in park, starter switch. Hope it is something simple and repairs stop piling up one on top another!

Well, got a new VOM and of course the Chinese POS was no good out of the box so I am waiting again on replacement. Even the Fluke ones that are hundreds of $ are Chinese.

In the meanwhile I did check all the battery connections and I did find one loose terminal but tightening it up did not fix it Terminals looked clean and they are new when I replaced the battery last year.

Grounds looked ok, and the connections seemed clean enough. Connections to the new starter seemed to be clean and tight also. I tried moving the shifter several times to see if the neutral switch might be the cause, but no joy.

So waiting for a working VOM and I will check further.

 

[Mogman]

Have you tried jumping the pos terminal to the start terminal on the starter?

 

[FlameRed]

Have you tried jumping the pos terminal to the start terminal on the starter?

Excellent suggestion. Why didn't I think of that?

When I briefly short the terminals, the starter does indeed spin. So the starter is ok.

I'll investegate some more once I get a good VOM.