g741.org

I've been inspecting the replacement frame that I acquired (because of this: http://www.g741.org/PHPBB/viewtopic.php ... ame+repair).

So far, it checks out against the specifications in TM 9-8031-2 Power Train, Body, and Frame for M37, Figs. 178 and 179. I started by leveling the frame (using a 4' level), checking fore and aft on the long flat area under the cab, and side to side at the rear crossmember, at the front transfer case crossmember, and at the front frame horns. Then I dropped a plumb bob from the various measurement points in Figs. 178 and 179, and marked the locations on paper squares taped to the shop floor. Measuring between the plumb bob points on the floor then produced the dimensions required in Figs. 178 and 179. The three diagonal pairs of measurements between the eight spring pins (Fig. 178) were either identical, or within the 1/4" allowed variance. Some of the other measurements (Fig. 179) were slightly different from the TM specs, but since no tolerances are given in the manual, I'm not sure how much variance is okay. Since the frame is square on the horizontal plane, I'm probably not going to worry about those small discrepancies.



What I am wondering about, however, is the twist in this frame. With the frame perfectly level side to side at the rear crossmember, the level across the front frame horns shows that the left front frame end is 17/32 lower than the right front frame end. Is this too much twist?

The frame that I'm replacing has the same twist, only much worse. But since both rails of that frame were cracked and welded at the engine crossmember at some point in its life, that frame's twist might be the result of improper alignment when the welding was done.

The twist in my "new" frame could be a manufacturing variance, or maybe something that was introduced over the life of these vehicles. If this was a car, I'd be concerned about panel fitment, but on an M37, the issue isn't so critical. Still, has anyone else found this sort of twist in their frame? Anyone think this is a problem?

Although it looks like you have your supported at only two points and should be getting GOOD measurements, when I had my frame bare I noted that even a variation in the shop floor was transferred to the frame. I found that the frames are so flexible it is very difficult to get the correct numbers, without the added support of springs and weight of motor, tranny, transfer case and the like. Like you said improper panel fitment should not be an issue later on and even if you found that a well placed washer would certainly bring it back within tolerance. I was much more concerned about corner to corner rack. Your mileage may very.

002

Thanks, 002.

I noticed the same flexibility in my frame when I was leveling and measuring it. After I was done taking the measurements, I unbolted and removed the rear transfer case crossmember, and discovered that the frame twist at the left front frame horn was down to 1/4" from the original 17/32".

Since the frame is square (and the truck won't be crabbing going down the road), I'm confident that the minimal twist won't be a problem. None of the frame welds at the boxed front and rear crossmembers are cracked or have been re-welded, so the flexing hasn't been beyond the limits of the frame at those points.

I have to keep reminding myself that these M37s aren't as precise and weren't built to the same tolerances that we're used to in modern vehicles.