I am in the process of restoring a 1970 M38A1 CDN3, and I have all the Manuals. In the Canadian Manual, it mentions the runout of the flywheel (0.008") on the outer edge, the runout on the flange the transmission mounts to (0.005") and the concentricity of the hole the transmission shaft mounts in (0.005").
So far the first 2 check out for me. The Last one however seems to be way out of spec. (.020"). That would mean that the crank and transmission are out of alignment.
I am trying to figure out if this is OK to mount like it is, or if I need a new bellhousing. I can't figure how this hole would be off. I checked a few times. There is no visible damage to the housing.
Any insight would be helpful.
So, I did some experimenting and found the following.
With just the dowel bolts attached, the runout is within 0.008'.
If I tighten the top two bolts on the bellhousing ( the ones at 11:30 and 12:30), then the reading goes up by 0.008".
Those bolts seem to pull up and warp the housing.
I am not sure if I should be concerned or not. Maybe I should just put it all together and run it.
I would completely install the flywheel by torqueing the 6 nuts diagonally until all are at the specified torque (35-41 FTLBS). Then check runout. Recommended max runout is 0.005.
wesk
My flywheel is OK. I have the 0.005" after torquing the bolts, Its the bell housing that is giving me a bit of problems.
After more research, and going through SNL-G-758, I discovered that what I thought were the correct dowel bolts, where in fact not. They where in the jeep and the fit was snug, but after some measurements, I find they are not the correct bolts. The thread was NC and the diameter was a few thou smaller than the hole.
I did a quick search of the vendors, and did not see those bolts. Anyone know who has them?
Then I will simply amend my last post to read: I would completely install the Bell Housing by torqueing the 6 nuts diagonally until all are at the specified torque (18-30 FTLBS). Then check runout.
The correct WO# 804367 dowel bolts:
Try Brent Mullins Jeep P{arts, He lists them $1.50 ea.
I am curious now after re-reading your post several times just what and how are you measuring concentricity of the bell opening with the dial indicator arrangement you are using. When I measure that I use the center of the rear of the dial indicator connected snugly to a straight shaft that slips snugly into the the center bushing of the flywheel. Then I turn the flywheel.
Exactly how are you assuring that the mount center of the dial indicator is in exact alignment with the center of the flywheel? Your photos show the center of the indicator no where near the center of the opening.
I don't beleive the mount needs to be in the centre of the flywheel, if that is what you are saying. As long as the indicator is mounted somewhere on the flywheel, the reading should be valid. The TM even mentions to mount the arm on one of the flywheel bolts.
Your current position is way off center giving you an elliptical track around the hole. I can't possibly see anyway you can extract anything resembling an accurate deviation quantity from true center. The purpose of determining the run-out on the hole in the bell housing is to determine if it is withing the 0.005 tolerance fit with the front of the bearing retainer on the tranny. The final object is to insure the tranny input shaft is dead center on the hole in the flywheel not one of the 6 flywheel bolts.
Yes, the object is to align the transmission shaft and the crankshaft. When a dial indicator is mounted anywhere on the flywheel and the flywheel is turned, it will indicate any out of round. The indicator can be anywhere on the radius. There is no eliptical movement possible, as the crank goes round.
The dial indicator spins with the crank and not on the mounting point.
btw. thanks for the information on where to get the dowel bolts, I should have them next week.
That page only addresses how to do the flywheel. Using the flywheel bolt circle as your starting point for determining runout of the opening for the tranny is extremely inaccurate. The original crank runout deviation will become larger when using the 6 bolt circle and in turn this larger initial runout error will add to the inaccuracy of your runout figures for the tranny opening. The only important bell housing opening measurement is the alignment of the center of the tranny opening with the center of the pilot bushing. This is easily checked by inserting a shaft in the pilot bushing that extends back thru the center of the tranny opening and then measure the center of the shaft to the edge of the tranny opening at 4 or more locations.
