Chevy & GMC Vans

One great thing about our T5s at this point is that you can install the whole clutch assembly in the bellhousing without the transmission installed and you can get really good measurements using the face of the bellhousing as a reference point to measure your depths at the pilot bearing, throw out etc. With an NV, You just cant do that.
Kinda sounds like your probs are on the backside maybe, but still, it will help with test fits.

Ok, I have good news, a little more good news, and a serious blunder that will now be very difficult to resolve.

good news 1-

I have eliminated the metallic noise, there is no more clicking and destruction noises. It seems this was again, the flywheel contacting the adapter plate bolts.

good news 2-

the clutch is now working quite well, so finally have that worked out.

good news 3-

the big tires look good, and only barely touch on some corners. I still have to put the wheel stops in, but they should work well. Secondly moving the bumper up has totally improved the look of the van by a huge amount.

comparison of before and after-





and now for the blunder. I make this admission because this is a crucial step I would never had made doing a 4-speed conversion on a benz, but rocketed right along on this van blowing right by it without thought, and have made some huge work for myself.

Some back history that should be funny considering that I know not to do what I did, and did it anyway. :mrgreen:
Basically, the 5cyl 617 motor is inherently hard to balance, its big and heavy and tall. For this reason, on an undetermined number of the 617 engines, engine balance is often made up on the driven plate of the flywheel. When you go to convert a 617 motor to manual that was formerly automatic, you MUST mark the original automatic flywheel with the crank, and have the manual flywheel match balanced with the original, as often as not, the original flywheel is not a neutral balance.

It suddenly occurs to me what the vibration is at low RPM (and its major). Its because I neglected to match balance the big aluminum flywheel with the existing benz flywheel from the 617 motor. Not only did I forget to do that, I also removed the benz flywheel from the donor motor WITHOUT marking it.

This means that I am pretty much screwed here on getting the balance right with no reference marks. I must have been on the 616 mindset thinking neutral balance, but ive blown it big time.

I can't think of any way to get the balance correct short of pulling the crank out and re-balancing with the flywheel. Unless I find a labor saving scheme to resolve this issue, this is what I think will have to happen now. whoops. heh, this thread is now dedicated to doing every bit of this engine conversion wrong 20 different times, and hopefully getting it to work in the long run.

On the plus side, the crank can probably come out in the van without too much issue.

WOW, sorry to hear about the balance problem, that does sound like a cluster. You're for sure right about the looks of the van,,, ACES on that.
You clearly know more about this engine than I, but are you sure there isn't a way to figure the balance position for the flywheel? That seems like a very easy mistake to make and one hell of a price to pay for it.

HPbyStan wrote:WOW, sorry to hear about the balance problem, that does sound like a cluster. You're for sure right about the looks of the van,,, ACES on that.
You clearly know more about this engine than I, but are you sure there isn't a way to figure the balance position for the flywheel? That seems like a very easy mistake to make and one hell of a price to pay for it.

a guy over on the benz forum gave me a great idea! (or at least an easier idea than major engine disassembly)
The two blunders I made were not match balancing the flywheel, and not marking the crank.

I can remedy the first one, I will have the aluminum flywheel match balanced to the one I pulled off the motor. Then its a matter of 12 possible positions for the flywheel, and one of them is definitely right. Even if I have to pull and mount the gearbox 12 times, that strikes me as less work and less parts than taking the motor apart.

The plan is to start at 12o'clock, run the motor without the gearbox and see how it vibrates, then go to 6o'clock, 9'oclock, 3'oclock, and so on. I might get lucky, and even if I don't, im bound to get the right position eventually just by process of elimination.

I want to build a jig to hold the motor up while mounted to the diff mount so I can watch vibration, and then I can start this process

Wow, Pulling out the crank does NOT sound like fun.
How many possible positions could that flywheel bolt in at?
(how many bolts hold it on)
Might be easier to try each position once till it runs smooth.
Might be easier that pulling out the crank, but I dunno, just a thought...
Can you look at where the balance on the flywheel is (on mine I can see where it is)
And try to determine where that ought to be in relation to TDC. Maybe you could just "figure it out"

Good Luck Bud. Keep us posted...

Well, that is a little better anyway. Sure hope you do get "Lucky" early on. Why in the world did "they" make all the bolt holes alike on an unbalanced crank or a least put in a dowel pin locater. That does NOT seem like good engineering to me.

doyoulikeithere wrote:Wow, Pulling out the crank does NOT sound like fun.
How many possible positions could that flywheel bolt in at?
(how many bolts hold it on)
Might be easier to try each position once till it runs smooth.
Might be easier that pulling out the crank, but I dunno, just a thought...
Can you look at where the balance on the flywheel is (on mine I can see where it is)
And try to determine where that ought to be in relation to TDC. Maybe you could just "figure it out"

Good Luck Bud. Keep us posted...

thats definitely what Im going to try first. To pull the crank, I have to remove not only the timing chain, but the oil pump chain. Im not looking forward to either jobs if it comes to that. Experimenting with each of the 12 positions seems more fun

HPbyStan wrote:Well, that is a little better anyway. Sure hope you do get "Lucky" early on. Why in the world did "they" make all the bolt holes alike on an unbalanced crank or a least put in a dowel pin locater. That does NOT seem like good engineering to me.

Im not sure, but the Germans always have a plausible and rational reason for every engineering scheme, however huge a pain in the ass it might actually be if you miss or skip an important step.

Possibly its so things can be re-clocked and fine tuned for balance. My understanding is that the cranks themselves are all balanced, but a certain percentage could not be fully balanced on the crank alone, and it was made up in the harmonic balancer, and or, the flywheel.

The stock flywheel I pulled off the donor motor definitely had some specific balancing, once I get the flywheels over to a machine shop, hopefully I can hear just how off center this balance might be from them

Do we know how they know where to bolt the flywheel on when still on the assembly line? Like with the crank @ TDC on #1, the balance weights go HERE ?

I'm thinking of my 4.3 bellhouse that should be on for the starter to bolt into the correct position and start the engine.
This has me wondering just HOW do you mount up your starter?????
I guess the fact that with a T5, you can install the bellhouse without putting the entire gearbox in as well, is a blessing if you are gonna try to run that flywheel in a few different clock positions around the crank, in hopes of "Finding" the right spot for balance.

Just installing the bellhouse without a gearbox should be a lot easier than stuffing the entire gearbox in a bunch of times till you find the right spot.

The 4.3 flywheel has a dowel hole so it only goes on one way, and you can visibly see the heavy spot on the backside of the flywheel.
Damn American Engineering ! Lol... Pretty hard to mess that up...

This situation really makes you appreciate design elements like that built into our vans.

Another one I especially like is the steering shaft on these vans, it only goes in one way and you cannot muck it up as hard as you try. If it had been made by mercedes, it would go in 35 different ways and require a special tool.

Right now im looking for a spare van, I need something I can use in the interim while im waiting on the flywheel for this thing. I have major projects on the horizon for work.

tinworm wrote:Right now im looking for a spare van, I need something I can use in the interim while im ......

Sounds like the story of my life.
](*,)
Why do you think I have owned 5 and a half vans now... Lol...

tinworm wrote:This situation really makes you appreciate design elements like that built into our vans.

Another one I especially like is the steering shaft on these vans, it only goes in one way and you cannot muck it up as hard as you try. If it had been made by mercedes, it would go in 35 different ways and require a special tool.

Right now im looking for a spare van, I need something I can use in the interim while im waiting on the flywheel for this thing. I have major projects on the horizon for work.

So, how DOES Mercedes install the flywheel on the assembly line ????? Not sure if inquiring minds would like to know but what's left of my miniature mind would.

HPbyStan wrote:

tinworm wrote:
So, how DOES Mercedes install the flywheel on the assembly line ????? Not sure if inquiring minds would like to know but what's left of my miniature mind would.

I have no real idea, but I figure they bolt the flywheel to a crank early on (or they did, seeing as its 30 years since anyone built these motors lol) in the assembly process, get everything fully balanced, then installed the crank with harmonic balancer and flywheel attached as a completed unit in to the block.

I'm pretty sure you can do that, since all the timing stuff is a chain that has to be crimped, and the crank seals are 2 part rope seals. All above is total conjecture though, I really have no idea how they do it

did a test to see if the stock benz flywheel had a biased balance to it

check this out, its got a definite heavy side.

http://www.youtube.com/watch?v=QAX6FiSh ... e=youtu.be

I was told the aluminum flywheel has a neutral balance, but now thinking on it, im not sure. I can't remember any drill marks indicating its been balanced. Once thats out im going to spin that too and see what it does.

Maybe I have a biased weighted flywheel incorrected installed on a engine that already had a biased weighted flywheel. That could explain a lot