m37 transfer case driveline angle

[Matthew Ziegler]

Several years ago, I installed a wc51 rear end in my m37 and moved the driveshaft to the driver's side transfer case output. around town the truck is smooth, last weekend was it's first long trip at 40-50 mph. At speed there's a fair amount of vibration. A diesel mechanic buddy checked it out and he feels the driveshaft angle is too steep. Has anyone tried switching m37 transfer case mounting brackets side for side? this would lower the driver's side of the case and dramatically decrease the pinion angle. The driveshaft is straight, has been balanced, new u joints a year ago. any suggestions are greatly appreciated.

[Tom Petroff]

I would not lower one side of the case for fear of a lubrication problem to the "high" side.
My suggestion if your angle is indeed the problem is, have the driveline shop install a CV joint.
The shop should be able to measure the angle for you and then know if it's in are how far out of Spec.
For a standard shaft.

Hopefully someone will come along that's had the same issue.
Tom

[Matthew Ziegler]

Thanks, looked into having a cv driveshaft made, the only 2 shops in my area wanted nothing to do with it. After a closer look switching the brackets side to side would be be too much and cause the case to hit the passenger side floor. Currently investigating shorter insulators in either rubber or polyurethane.

[Matthew Welcher PWA]

Can you send pictures of your Driveline angle? The M37 from the factory is a pretty sharp angle to start with. I cannot tell you exactly, is the vibration still there if you slip the transmission into neutral and or push in the clutch? While at that speed?

[Matthew Ziegler]

Sorry I can't currently post pictures. However I've found a practical solution for the problem. I noticed that there's a steel tube with a cupped end welded to the bottom of the transfer case brackets at all 4 mounting points. I carefully removed these with a cutoff wheel and welded them on the top of the brackets. This allows for use of the stock transfer case rubber isolators and hardware while lowering it just over 5/8 of an inch. This also keeps the transfer at the factory angle for oil capacity. I have one side done and reinstalled, will finish and paint the other side this evening. once this is done I'll check my angles and get some pinion angle shims to dial in the rear u joint angle. I may resort to removing one short leaf for an extra .250 of drop. I am going to have to machine down the passenger rear companion flange on the transfer case ( no longer used) as it looks like it's going to be very close to the rear transfer case crossmember. The front driveshaft angle should be fine since I installed new front springs with 2 additional leafs several years ago anticipating a diesel conversion down the road. This resulted in around 3/4 inch of lift. I may have to shim the front motor mounts up slightly to adjust the trans to transfer angle but I think it'll work out and operate a lot smoother. This is kind of labor intensive but so far the biggest expense looks like it'll be some steel pinion angle shims.

[Jason Mills]

I have heard of some sort of Cell Phone application (I do not own one, so I am not much help) that can be used to diagnose Noise,Vibration, Harshness issues in a vehicle while driving. I will need to look for where I came across that info, but am willing to seek it out if you are interested.

[Matthew Ziegler]

Thanks for the thought but haven't gotten a smart phone yet... I'm pretty much inept with modern electronics. I'm often teased about still having a flip phone.

[Matthew Ziegler]

I finished it, The driveshaft was at 19.5degrees, now sits at 17.3 degrees. the u joint angles top and bottom are supposed to be at identical or very close angles, my transfer case is angled .5 degrees down at the rear and my pinion is angled 1.6 degrees up. Before the transfer case was 1 degree down and the pinion was facing 7 degrees up. there is almost no vibration in the driveline, vastly better than what it was. According to my research the driveshaft angle shouldn't exceed 15 degrees, I can't see any way of achieving this without major modifications. Another website pointed out that most lifted jeeps greatly exceed the angle of my truck with the only issue being slightly reduced u joint life. I put about 10 miles on the truck late last night at different speeds, pushing the clutch in going down hill, anything I could think of, I'm impressed.

[Matthew Welcher PWA]

Matthew, Glad you got this figured out. thanks for keeping us updated.

[tuko]

How is the intermediate driveshaft angle on your stock trucks? I centered my motor and trans and it’s a few inches off from the input side of the factory transfer case.

[Matthew Ziegler]

Tuko, the intermediate is straight back from the trans and angled down, I measured it but didn't write it down. I remember it was under 15 degrees and the u joints were almost perfectly parallel so I wasn't concerned. as for side to side, from what I've read as long as it's under or reasonably close to the 15 degree maximum you'll be fine. Thinking about it, I'm using the driver's side output on the transfer which is a few inches off center.

[tuko]

It seems as if the stock motor must be off center or is the factory intermediate driveshaft off from side to side? I never paid much attention to it in stock form.

[Matthew Ziegler]

Tuko, I crawled under the truck tonight, the motor and trans are not centered measuring from the inside vertical frame rail to the np420 drain plug ( center of trans) I got driver's side, 14 inches, passenger side 18 and three eigths. for the front you can probably measure to the hole in the front bumper for the hand crank, should be pretty close.

[tuko]

Tuko, I crawled under the truck tonight, the motor and trans are not centered measuring from the inside vertical frame rail to the np420 drain plug ( center of trans) I got driver's side, 14 inches, passenger side 18 and three eigths. for the front you can probably measure to the hole in the front bumper for the hand crank, should be pretty close.

When I put in the new motor I centered it. It’s steep (side to side) but don’t have any vibration. I may eventually try to sneak the TC over a hair to split the difference between the rear shaft and intermediate?