I need to source a new flexplate

[DaemonForce]

I have two identical flexplates that have been previously bolted between the stock AMC 4.2 and Chrysler A-998 tranny. I intend to continue using this automatic until it fails but that engine failed nearly a year ago. In its place will be a much bigger 4.7L but I'm starting to wonder if there's any real difference between the 4.0/4.2 blocks. The exterior spacing should be about the same but I'm assuming the next plate will be the same size. That's where I need help. I'll be using the 4.2 crank but because of EFI and my avoidance of crappy overpriced Hesco kits, I'd rather do this the Chrysler way with a tone ringed flexplate. Last week I actually managed to get SOME useful data out of the parts guy at the dealership. A 91-92 Wrangler with a 42RE is P#53006328. I don't need to question if it will work with the engine electronics but will this fit an A-998 or do I need a different flexplate?

[eaglefreek]

I don't think the YJ Wrangler ever came with a 42RE. I thought they had a 32RH, which is basically a TF999. I used a 91-95 YJ flexplate in my Eagle when I had the 998, so I could use the "newer" style starter. 

[BenM]

There's a wrangler flexplate with the 998/999/32RH that connects to the 4.0. You just have to drill a hole and mount a bracket to hold the sensor to read the tone ring. Don't use the AX4 plate. I forget which starter it takes.

[DaemonForce]

There's a wrangler flexplate with the 998/999/32RH that connects to the 4.0. You just have to drill a hole and mount a bracket to hold the sensor to read the tone ring. Don't use the AX4 plate. I forget which starter it takes.

The starter matches the flexplate that was intended for factory use. If it's made for a 258, use the 258 starter. Otherwise you get explodey parts. That's not a good thing. o.O It sounds like I'll have to change starters as well.

I was under the impression that I would need the flexplate that sees action between the 4.0 and AW4. What's wrong with it and what do I really need? I'm not picking a full size flywheel. This is a Wrangler part, I know that much. If there's no difference between the back end of the 258 and 4.0L and I want to reuse my A-998(32RH?) then what's different? I know the Chrysler guy isn't going to tell me.

Here's what I'm looking at:
The part is going to be 91-95 from SOME kind of Cherokee/Comanche(91/92)/Grand Cherokee(1993) or Wrangler that has the 4.0L and either the simple 32RH or electronically communicative AW4 or 42RE. I cannot tell the difference between the AW4 and 42RE. I know a 32RH when I see one because it's a pain to get to the shifting mechanism when I'm unable to drop the crossmember(Picking yards typically perch Jeeps right under the crossmember). So that's a thing.

Oh and there's another part number. I really have no idea what the difference is between the two but either one fits? Why?

[eaglefreek]

I have no idea if there is a difference between tone rings between the YJ with a 32rh and XJ with an AW4. That's something you'll have to find out. If there's a difference, just use a YJ ECU with the appropriate YJ flexplate and starter. It is real important to match the hole location for the CPS so the computer knows where TDC is.

[DaemonForce]

I have no idea if there is a difference between tone rings between the YJ with a 32rh and XJ with an AW4.

I'm going off of this post for accuracy.

If there's a difference, just use a YJ ECU with the appropriate YJ flexplate and starter. It is real important to match the hole location for the CPS so the computer knows where TDC is.

That's really easy for everyone here to say and it shouldn't be a problem but it's starting to look like I'm thinking about this backwards. Should I be focused on getting the electronics BEFORE I even think about the flexplate? I mean, I already have a somewhat clear idea that the flexplate is going to come out of an OBDI Jeep with the 4.0L and an electronic automatic bolted up. I know that's going to be easy to find. What's HARD to find is the (in)complete 91-95 wiring harness from a Jeep with a 4.0L mated to a gearbox. I never see them anymore and if I do it's some torn up Comanche that has been completely wrecked and impossible to pick.

The 86-91 Comanche: The NW junkyard's new Wrangler.

[eaglefreek]

If you're stuck on using the 998, then you'll have to do some homework and figure out  if the YJ and XJ PCM's get the same or different signals. When you look at the amount of time and work to get a donor harness and thin it out to drop in the Eagle, the Hesco harness looks like a good deal. However, if you're like me and have more time than money, a junkyard harness makes sense. After installing an AW4/242 combo in my Eagle. I would skip the 998 and go for the AW4 if I was doing a EFI stroker swap.

[DaemonForce]

Homework is stupid. The whole point is to get less of it. You already lost me there. Way off the curb. *bounce* (*･ω･) Lets just deal with this thing in a way that makes sense.

The current goal is to reuse my torqueflite until I can no longer use it. By then I intend to swap in whatever 5/6 speed gearbox that should be more appropriate when I reach that point in my life(about a year or two). See I'm not really stuck on the automatic because it's an automatic or because it's original Eagle equipment. It's because it's all I have to work with at the moment while my $$$ resources are stretched out of existence by grandpa's fleet of 72 Ford pickups. The only reason I'm even on this topic right now is because one of his junk Fords blew up and now I'm driving the only decent vehicle sitting in our yard. Thank God the T-18 is easier on mileage than the C6. If I had the cash, I would toss that stupid 390 Ford garbage for the nice little 240 sitting in the Nisqually yard. I'm convinced the Eagle is the only vehicle that lets me hold onto a dime as years of my life has proven solid. I need to get this thing running right on as little $$$ as possible just so I can earn a fair living like a normal human being.

[carnuck]

The torque converter changed slightly when they went to the 4.0L style starters. It has an even bolt pattern on it (same as that flexplate) BUT the teeth are 3/8" (10 mm actually) closer to the motor. If you use that flexplate redrilled for the 998 pattern, the converter is either pulled out or pushed in a bit (head is fuzzy. hard to think) which will either destroy the front pump, or ride so close to the edge that a hard acceleration may shatter the pump teeth by pulling out and breaking the converter neck.
   To find out, measure from the web of the flexplate (where the converter bolts on) to the edge of the 4.0L block (without the splash plate) and measure with the new one on and 2 bolts attached (line up the converter holes while it's apart and mark the converter through one of the BIG holes for aligning during install.

[DaemonForce]

The torque converter changed slightly when they went to the 4.0L style starters. It has an even bolt pattern on it (same as that flexplate) BUT the teeth are 3/8" (10 mm actually) closer to the motor. If you use that flexplate redrilled for the 998 pattern, the converter is either pulled out or pushed in a bit (head is fuzzy. hard to think) which will either destroy the front pump, or ride so close to the edge that a hard acceleration may shatter the pump teeth by pulling out and breaking the converter neck.

That's a pretty serious issue and one that I'm concerned about with the difference in flexplates. So the A998 and A999 pieces are different enough that the starter, flexplate and torque converter are most likely specific to the parts combination. Worst case scenario I may end up changing torque converters?

To find out, measure from the web of the flexplate (where the converter bolts on) to the edge of the 4.0L block (without the splash plate) and measure with the new one on and 2 bolts attached (line up the converter holes while it's apart and mark the converter through one of the BIG holes for aligning during install.

I'm fairly poor with the measuring tape and having good lighting instruments with me when I need to crawl under vehicles but luckily this approach means that I won't have to buy each individual flexplate to do the comparison since the engine blocks in question are virtually identical.

I understand the Eagle flexplate holes are spaced 10" with a diameter(and maximum inner bell diameter) of 14" with an unknown depth. Unfortunately both of my cranks are currently being reground and my only shot at getting this done is the short picking expedition that I have to take this afternoon. I'm not so hung up about the flexplate because it's common enough that I can still get a shiny overpriced one from the dealer but it's still a drag because it's such a critical component. That 10mm is a pretty big shift in size to just neglect and hope for the best when this could cost me the entire vehicle 3x over AGAIN so I don't plan on doing that. I'm seriously surprised that this matter hasn't been covered here before. Of all the 4.0L swaps, nobody has documented how they retained solid functionality with their A998? This is sloppy and very discouraging. I'm starting to think I should just get a cheap Hornet.

[carnuck]

The 998 needs no external inputs to control it aside from passing gear lever. The solenoid in the 999 valvebody does it electrically.

You can tell which offset the flexplate is by the style of starter. Ford style starter ring gear is 3/8" deeper. XJ style is 3/8" closer. XJ starter won't reach the teeth of Ford style ring gear. Found that out when I tried to fire the 401 I had to sell last year.

[DaemonForce]

The 998 needs no external inputs to control it aside from passing gear lever. The solenoid in the 999 valvebody does it electrically.

You can tell which offset the flexplate is by the style of starter. Ford style starter ring gear is 3/8" deeper. XJ style is 3/8" closer. XJ starter won't reach the teeth of Ford style ring gear. Found that out when I tried to fire the 401 I had to sell last year.

I got a flexplate from a 96XJ that had an AW4 behind it at some point. The bolt pattern does not mate up to my 5333LS(GoPNH) torque converter. The overall diameter is the same implying that it should fit. What needs to go? The flexplate I just pulled or my old torque converter?

[carnuck]

AW4 plate is different from 999 TJ/YJ plate.

[DaemonForce]

AW4 plate is different from 999 TJ/YJ plate.

So I absolutely need the plate from a 91-95 YJ? I have a choice of going back to the Wrangler yard(never thought I would ever find such a thing) or go to the dealer. Right now I think I would rather visit Chrysler for a new plate.

[carnuck]

The flexplate offset changed as well in '88 to use the 4.0L style starter (Chrysler didn't want to run Ford starters)