Transfer case vibration

D

Duly

Member
Now that my traveler is running good I have decided it is time to fix other things. Here is the problem, after I added the 4 inch SUA lift, my transfer case has begun to make a deep sounding rattling noise when in 4wd high. To fix this, and get a better front drive shaft, I called Tom wood's. I gave them the measurement from yoke on differential to yoke on front of transfer case, and put it in, that didn't fix the problem. I changed the fluid last night in the transfer case (50w valvoline), the noise is reduced, but still there. Also, when I try to turn I have problems turning just a little, it seems like the truck jerks, and is under stress. When in 4wd high and hubs locked if I accelerate it feels like the whole front end is vibrating. None of these things happen when in 2wd high, smooth going. If any of this doesn't make sense please let me know, it is hard to explain things in writing sometimes.

Thank you for any help,
duly
 
After a weekend of working through scenarios as what the problem could be, it has come down to the driveshaft angle. I took the driveshaft out and drove in 4wd high, no problem. Then locked the hubs in, no problem. Now unless I am missing something the driveline angle is the problem. Any ideas to fix this problem are appreciated.

Duly
 
1) perform a complete overhaul of the transfer case including replacement of all bearings.

2) do not drive in four high or low on hard-paved surfaces with the hubs locked (or unlocked) unless the road surface is covered in snow/ice mud/dirt/rock.

With no front driveshaft installed, there can be no vibration induced through the transfer case unless it has an internal issue(s) that are also present when the only the rear axle output is "loaded". When the front driveshaft is present, then a wear-related vibration inside the transfer case can be greatly magnified under load.

Are you certain that both front and rear axles have the same ratio gears installed? Are all four tires within 1/32" rolling circumference of each other? Is the front differential an "open" unit, a limited slip, or a locker of some sort? If limited slip, are you certain it's working correctly?

Are you certain that the front axle u joints (stub end), the inner axle stub/spindle bearings, the hub/hub bearings, and the locking hubs are all correctly serviced/lubricated/adjusted? Are you certain the locking hubs actually unlock when ya tell 'em to? On both sides??

Is the tire pressure exactly the same and the tire circumference exactly the same on the front tire set??

These part time transfer cases do not have a "center differential" like "modern" throwaway all wheel drive vehicles do. They are not to be operated in four high or four low on a hard surface where the individual tires can't slip when the driveline gets "wound up" due to the lack of a center differential.
 
Thank you for that. I now have many things to look for. Yes the same ratio in both axles, like I said they were both recently rebuilt and I installed everything except the gears. Front axle is open. Since everything Was replaced very recently in both axles all is tight and lubed. And the hubs unlock. Tire pressure is all at 35 psi, just did that yesterday. I don't understand one thing about these old trucks maybe you can explain: when hubs locked and in 4wd high I have a hard time turning left or right, seems like the truck jerks and is difficult to turn the wheels, is this normal? Or part of my problem? Thank you for taking the time to help.

Duly
 
If you're trying to turn on a hard surface with the hubs locked & the tc engaged, that's due to binding of the drivlines. You'll notice this most when trying to turn. In other words, that's normal. However, don't do it! Driving in 4wd on a hard road surface which allows no wheel slippage can ruin the gears/drivelines. 4wd should only be engaged on dirt, gravel,sand, snow, ice... Bascially a surface that allows the wheels to slip.
 
Matt's got it!

Because these "conventional" 4x4 rigs have no "center differential" or torque biasing device/ability, you will experience this type of operation due to the "binding" effect. You May see the same thing when you try and shift back into 2wd and the transfer case stick is "stuck"...ya have to reverse/back and fill and play with the stick to get the case to shift out due to internal binding. Some are better, some are worse.

I've driven thousands of miles in a conventional 4x4 peekup (my own) in four high and in four low, with chain/cables on the front axle, pulling a trailer in heavy accumulated ice/slush/snow on a hard surface highway at up to 40mph. Because the tire/chain combo can "slip" on the ice/snow, ya don't notice the binding except in a slow speed turn, but it's there. But try that on a hard surface with no ability to slip the tires, and in even a slight turn, the binding will really get your attention!

In winter conditions here where we live, I never unlock the front hubs on my rig, and with practice ya can shift on the fly from 2 high to 4 high on the fly just like one of these modern throwaway 4x4 rigs. But at that speed, with chains on and the aggressive tires I use year 'round, the vibration can be very noticable and that's not due to any driveline angle/u-joint issues.

Keep in mind that in the beginning there was no such thing as "locking hubs" and many "conventional" 4x4 vehicles came oem with drive flanges on the steering axle! When the fulltime 4x4 stuff was intro'd in the early 70's, those rigs incorporated a center differential of some sort...and still do. And immediately the aftermarket geared up with "part-time conversions" for those!
 
Thank you both for that information, I needed to learn about how these old powertrains work. Very thorough explanation. I am planning on rebuilding my transfer case and we will see what happens. Is there a preferred rebuild kit? I am all for using the right stuff and hylomar for the gaskets, so can I just get the bearings I need? Thank you again for the help. And yes this will be my first rebuild of the t-case, and yes I have a service manual.


Duly
 
The ihon rebuild kits for the d20 are complete, gaskets/seals/"o" rings. You will also need a bearing set and ya need to know "which" idler/intermediate shaft you have, you can do a rudimentary measurement of that externally since the end protrudes from the case. It "should" be a 1-1/4 shaft but on rigs that have been around for years, anything is possible due to po virus and parts swaparoos. The shaft diameter is important to know so you can get the correct bearing set, those are loose needles.

The IH service manual is fairly decent for rebuilding the d20 case if your copy has photos which are legible.

I use no sealant on the gaskets, they weren't sealed when the case was originally assembled.

One "most" of the cases there are two small welch plugs that will need to be removed and replaced with new, those won't be in any rebuild kit I've ever used but May be sourced at any fullservice auto parts or ihon has those also. In some cases, those points are "sealed" with what appear to be rubber plugs that you May be able to r&r.

If you are interested in the "twin stick" mod for your project, now is the time to prep the tc for that also so you can do it right, ya don't have to install the new stick set at that point if you are on a budget, but you will have to be careful in how ya shift the tc if ya don't install the twin stick setup after modding the interlocks.

Before starting on the case, call Jeff directly at ihon and discuss your project and he can advise on exactly the parts ya need.

This is not gonna be a Saturday morning project and a steep learning curve is possible unless ya have an experienced assistant with proper tools to help! Give yourself several days for this so if your sii is a dd ya need to line up alternative transportation!

Cleanliness is your best tool! And some folks try and get by without replacing bearings as that can be a pain...which is exactly what will be wrong! If all suspect parts aren't replaced, that's not an overhaul, that is just a teardown and cleanup!
 
I guess I need to call about the rebuild. I don't plan on it being a quick and easy project, in fact I am getting another t-case and I am going to rebuild it so I will still have something to drive. As for the twin stick conversion this is the first I have heard of it. I have to say it would be unique to see a twin stick in a traveler. So how involved is converting a Dana 20 to twin stick?

Duly
 
duly said:
I guess I need to call about the rebuild. I don't plan on it being a quick and easy project, in fact I am getting another t-case and I am going to rebuild it so I will still have something to drive. As for the twin stick conversion this is the first I have heard of it. I have to say it would be unique to see a twin stick in a traveler. So how involved is converting a Dana 20 to twin stick?

Duly
Click to expand...

Your plan to use a different transfer case for a learning experience is excellent! That is the best way to do this, the pressure is off and you can take your time.

Be careful though regarding all the d20 variations...you May encounter a situation where a case was mated to transmission and the incorrect input gear (or the slang term "bull gear") was used. There are multiple input gear spline configurations used, and those will be specific to it's mating gear in the transfer case. The issue involves the helix angle of the various gears that were used between Ford, IH, Jeep, etc.

Currently, this information/matrix on the novak site is fairly decent but is not complete! I've been working on a more complete reference (similar) that is specific for IH stuff but it's taken a back seat to many other projects, that's the kind of stuff I do in the winter!

So try this:

the novak guide to Dana 18 & 20 gears interchange

The key to making a correct match to these parts is the spicer-Dana part number that is present on each part! The mating parts must match the part numbers, and the information in the chart above is accurate in that regard for IH stuff.

Alotta "vibration" and noise issues regarding transfer cases are because folks just indiscriminately swapped input gears around just because the spline count matched...but the problem is the helix angle does not match. Yes, the incorrect parts can be forced into mesh, but it puts a tremendous stress on the entire case system resulting in noise/vibration/failure.

So...my caution is don't put alotta effort into building a d20 that you don't have the right bull gear match for! Some IH-version bull gear variations have become extremely hard to find that are useable...it's not problem with the teeth of the gear, the problem lies in the badly worn "dogs" on the end of the gears. Also, it's real common to find the nut which retains the bull gear onto the tranny output shaft to be loose.

As for the "twin stick" deal...that is a very common mod for any rig that uses a single stick d20 (or np 205 for that matter). Do a search for keyword "twin stick" and you will have reading material for weeks! A twin stick setup inna traveler is no different than for a Scout 800 or Scout II...the traveler is just a longer wheelbase with the extra length added to the frame behind the transfer case mount/crossmember. I just mention that because if you do desire a twin stick setup in the future, the time to perform the mod is while it's in pieces on the bench!
 
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Sounds good, I will check the input gear on the "new" transfer case and make sure it is the right one for the d20. This is the reason for the rebuild of a d20 that's already out, I can do the rebuild slowly.

Thank you for the help,
duly
 
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