Posted by Brian in Oregon on Wednesday, June 19, 2002 at 11:53AM :
In Reply to: V-8 in a power wagon posted by jock on Wednesday, June 19, 2002 at 10:26AM :
We've had this conversation on the M37 Forum (link at the top of Joe's page), and have also taken a poll.
There is no clear cut limit to what the axles will take. They are the weak link. SOme folks running big blocks have never had a problem, while some running the original flathead have. Tire spin and sudden gaining of traction has a lot more to do with it than anything. Of course, it is easier to spin a tire with the V-8, but that does not neccessarily damn the V-8. A locker will help a lot, because it more evenly divides the load strain between the two axle shafts.
The M37 axles can be pretty much summed up as Dana 60 differentials with Dana 44 axleshafts.
Aftermarket axles are made, running from $300 to $800 a pair. A poster by the name of Daniel on the M37 Forum is making bomb proof axle shafts for the M37.
The transfer case is a relative of the NP205. It has about the same strength. Power is not a real issue. What is a real issue is the noise level, especially as you go faster and faster above 45 mph. Also, the output is not from the center to the rear axle, but off the side. Thus the transfercase has the entire geartrain under load even in 2WD. This also raises the operating temp by about 50 degrees. It is possible to center the output with a replacement rear axle, but this works better on a PW, M43 or V41/M201 than the M37 because the M37 as a short enough wheelbase that the axle may strike a crossmember at full articulation. Crawl under the M37 and look at the center of the e-brake hub and then look at the crossmember above it and you'll get the picture.
Keep in mind that 3200 rpm will be needed with 5.83 gears and 900x16 tires to run at 55 mph. A modern V-8 should be able to do that all day long. It is possible to go faster, but the noise level is awful. IF someone wants more speed, then larger tires and/or a change to 4.89 gears makes sense. If you run at 65 mph with one or the other, you aren't gaining a lot from a noise standpoint. But both 4.89 gears and larger tires will reduce the rpm and reduce noise.
Anyone considering a V-8 should consider a disc brake upgrade to be mandatory. The M37 brakes are simply not up to the task of stopping it quickly at speeds of 55 mph or faster.
I have the Helitool 318/360 and disc brake kits. They are well engineered. No permanent modifications need to be done for the disc brakes, other than a couple of minor holes for brake lines for a mster cylinder upgrade. The V-8 kit requires a small eyebrow for clearance in the frame, and one altered transmission mount. These can be reversed. Thus the M37 is restorable to original condition.
The Helitool V-8 kit gives a choice of the original 88950 or NP420 transmission (allowing use of the PTO for the winch) or you can put in a more modern NP435. You could also use the forward part of the kit and a short tailshaft 727 automatic, but it is a very tight fit. I don't know anyone who has used Ray's kit to put in a 727. The original transmissions, 88950 or NP420, are not synchro in 1st or 2nd. On level ground, with a V-8 and original 5.83 gears and 900x16 tires, 3rd gear starts are the norm. You shift into 4th at around 10 mph and can basically cruise around in 4th except when coming to a stop.
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