scguy Posted February 29, 2020 Share Posted February 29, 2020 So I've got the engine mostly together on my 89 Comanche. Engine setup is 92 HO short block, the 93 HO head (7120), AW4, flexplate, and the starter are all from the same 93 XJ donor. When I crank it over, it makes this scraping sound. It doesn't make it if it's running, only with the starter engaged. I've tried another starter I had lying around, same issue. Flexplate isn't cracked, the bolts are tight, and the teeth are fine. No rub marks anywhere on the flexplate, bellhousing, or starter. Any ideas? Link to comment Share on other sites More sharing options...
Pete M Posted February 29, 2020 Share Posted February 29, 2020 can you watch the flywheel spin while it cranks? Link to comment Share on other sites More sharing options...
scguy Posted February 29, 2020 Author Share Posted February 29, 2020 can you watch the flywheel spin while it cranks? Yes, it seems like there's a small variation when turning, but probably no more than 1/16 inch. Link to comment Share on other sites More sharing options...
Eagle Posted February 29, 2020 Share Posted February 29, 2020 18 minutes ago, scguy said: 24 minutes ago, Pete M said: can you watch the flywheel spin while it cranks? Yes, it seems like there's a small variation when turning, but probably no more than 1/16 inch. Should be zero. Cracked flexplate? Link to comment Share on other sites More sharing options...
Pete M Posted February 29, 2020 Share Posted February 29, 2020 it certainly sounds like it happens once per revolution and it's identical each time. Link to comment Share on other sites More sharing options...
Jeep Driver Posted February 29, 2020 Share Posted February 29, 2020 Yeah, sounds like a bad flex plate or gear ring. Link to comment Share on other sites More sharing options...
scguy Posted February 29, 2020 Author Share Posted February 29, 2020 The flexplate was fine when I installed it, I tourqued it to spec. I reckon I can pull it apart and see. Edit: fine as in not cracked. Link to comment Share on other sites More sharing options...
jdog Posted February 29, 2020 Share Posted February 29, 2020 Do you have the starter shim in? Stock 1988 swb 4.0 ax15 np 231. Link to comment Share on other sites More sharing options...
scguy Posted February 29, 2020 Author Share Posted February 29, 2020 Do you have the starter shim in? Stock 1988 swb 4.0 ax15 np 231. The metal plate between engine and trans? Yes Link to comment Share on other sites More sharing options...
eaglescout526 Posted February 29, 2020 Share Posted February 29, 2020 2.5L starter has the shim 4.0L does not Link to comment Share on other sites More sharing options...
omega_rugal Posted February 29, 2020 Share Posted February 29, 2020 the starter and the flywheel teeth are slighty misaligned Link to comment Share on other sites More sharing options...
scguy Posted February 29, 2020 Author Share Posted February 29, 2020 I pulled the transmission, don't see anything rubbing, so I'll be installing a new flexplate. Link to comment Share on other sites More sharing options...
Warren Mohler Posted February 29, 2020 Share Posted February 29, 2020 Are the dowels engine to trans in place? Link to comment Share on other sites More sharing options...
scguy Posted February 29, 2020 Author Share Posted February 29, 2020 Are the dowels engine to trans in place? Yes Link to comment Share on other sites More sharing options...
Eagle Posted February 29, 2020 Share Posted February 29, 2020 8 hours ago, scguy said: The flexplate was fine when I installed it, I tourqued it to spec. I reckon I can pull it apart and see. Edit: fine as in not cracked. The typical crack is hard to see even if you know to look for it. It's usually around the outer diameter of the bolt reinforcing ring. Link to comment Share on other sites More sharing options...
Dzimm Posted March 1, 2020 Share Posted March 1, 2020 Did the trans slide nicely into the crank? If you had to use the bolts to cinch up any Gap it's likely not aligned properly. It should slide right up flush with the block easily. It's surprisingly easy to screw it up if you aren't careful, I learned it the hard way and had a crazy grinding/scraping sound when trying to start. Link to comment Share on other sites More sharing options...
scguy Posted March 1, 2020 Author Share Posted March 1, 2020 Yes they mated easily and didn't have to draw them together with the bolts. I bolted them together out of the truck and put the engine/trans/transfer case in as one unit. Link to comment Share on other sites More sharing options...
Warren Mohler Posted March 1, 2020 Share Posted March 1, 2020 I will assume you used the proper starter bolts. Can't imagine what could be wrong that you would not be able to see, I have replaced a lot of flex plates due to cracks even had one that the entire center was broken and still started without such noise just sound bad running. I would put a dial indicator on and see how far it's out before spending too much $ Link to comment Share on other sites More sharing options...
scguy Posted March 1, 2020 Author Share Posted March 1, 2020 Here's the flexplate in question. Don't see any cracks, but I'm sure I saw a difference like it was off center when turning it over. Was going to install a new one today, but the parts store lost it, so... I don't have the original starter bolts, but I have ones of the proper length, thread and grade installed. Link to comment Share on other sites More sharing options...
Warren Mohler Posted March 1, 2020 Share Posted March 1, 2020 It has been a while since I put one on, if I remember right the lower bolt has a shoulder that may position starter to ring gear. If new flex plate does not fix problem try to pry starter away from flex plate and tighten, a few thousands will make a big difference Link to comment Share on other sites More sharing options...
omega_rugal Posted March 2, 2020 Share Posted March 2, 2020 22 hours ago, scguy said: but I'm sure I saw a difference like it was off center when turning it over. that, if you can notice it then is too much Link to comment Share on other sites More sharing options...
scguy Posted March 2, 2020 Author Share Posted March 2, 2020 So under further inspection, I've found the flexplate has about .015" of play around the crank. The new one does as well. They are the correct flexplate for the application. Unless someone tells me why I shouldn't, I've used feeler gauges to space it evenly and torque it down. I imagine it was off center before, causing the starter gear clearance to change. Link to comment Share on other sites More sharing options...
scguy Posted March 3, 2020 Author Share Posted March 3, 2020 Being the cheapskate I am and having blatant disregard for my labor time, I decided to try the old flexplate with proper spacing. Result: same problem. So back apart it came. Managed to pull the trans, remove and install the new flexplate and back together in 45 minutes. Of course, it helps to have no driveshafts in or trans cooler lines hooked up. Result: fixed. Should have done it the first time, but I took a shot at saving $100. Measured the old flexplate then and found discrepancies of at least .060" out of round. So this one is solved. Finally. Link to comment Share on other sites More sharing options...
Pete M Posted March 3, 2020 Share Posted March 3, 2020 solved! doesn't much matter how ya got there as long as success is at the finish line. Link to comment Share on other sites More sharing options...
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