Need help troubleshooting trnasfer case issue
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Mountain Pass
Joined: Jul 2016
Posts: 146
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Need help troubleshooting trnasfer case issue
The case and 4 wheel drive used to work great. I was driving on snow and went around a tight corner (driveway) that was dry, it was stalling as it tends to do when in 4x4 and something gave way, I was only doing 2-3 mph. I thought it was a tire skipping at the time but I went to use it today and something is off. There is heavy vibration 5-10 mph and a mild gear on gear noise from 5 down to 0 when decelerating with the clutch in. It moves into and out of 4 hi and low easily but if I drive it at all I have to fight like hell to get it back out.
Whatever is broken is somewhere between the transfer case and transmission interface and the front wheels. What's the typical weak link? Is it relaceable? What are some test I can do to help troubleshoot it?
The truck drive great in 2 wheel and the trans shifts just fine.
'77 f150
Np435 trans
Np205 transfer
4:11 front and rear, open d44 and 9in lsd.
Let me know what other information will help.
Thanks guys.
Whatever is broken is somewhere between the transfer case and transmission interface and the front wheels. What's the typical weak link? Is it relaceable? What are some test I can do to help troubleshoot it?
The truck drive great in 2 wheel and the trans shifts just fine.
'77 f150
Np435 trans
Np205 transfer
4:11 front and rear, open d44 and 9in lsd.
Let me know what other information will help.
Thanks guys.
Junior User
Joined: Nov 2017
Posts: 74
Likes: 1
From: Mokelumne Hill
MattMac, all I can say is the NP205 is an animal and built like a tank. Not sure of any pattern failure at all with it. I have rebuilt plenty of them but yet to see a broken anything in them. They are gear driven as you know. Now if it is a NP203 by sheer chance then you may end up with the internals shaking hands with you. The 205 has the three cover plates on the rear of the case. Hopefully the struggle you mentioned taking it out of gear is not from axle wrap caused by different diameter tires. You can also drain the oil in the TC and see if any metal in it. Honestly it is hard for me to think anything would let go from what you described unless the lsd held firm on a turn, then maybe a spider or side gear munched. I would not rule out the differential as having some sort of failure.
Thread Starter
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Mountain Pass
Joined: Jul 2016
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Okay, I just assumed that the resistance had to be the TC. Actually, that would make sense, it fights in both low and high, low shouldn't haven't been effected. What do you mean by axle wrap? I'm now thinking maybe a blown front diff. The TC would have been better, I can get a NP205 for $150 on craigslist any day of the week. I can't imagine what getting the diff rebuilt is going to cost.
I'll put both axles up on blocks, put it in 4 high, let her idle in gear and see if I can chase down what's broken.
I'll put both axles up on blocks, put it in 4 high, let her idle in gear and see if I can chase down what's broken.
Senior User
Joined: Aug 2017
Posts: 156
Likes: 1
From: Farmville, NC
memories from back in my 4wd truck days, jack up one front wheel station with 4wd engaged but engine not running. try spinning the wheel. Hopefully it won't turn. The sound you describe makes me think of torque wind-up which had a tendency to snap driveshafts in the axle casings.
My next thought would be to remove the t/box to front axle driveshaft then attempt to engage 4wd. If the symptoms you describe remain - trouble disengaging 4wd - then that would indicate a transfer box problem rather than a front driveline problem.
My next thought would be to remove the t/box to front axle driveshaft then attempt to engage 4wd. If the symptoms you describe remain - trouble disengaging 4wd - then that would indicate a transfer box problem rather than a front driveline problem.
Thread Starter
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Mountain Pass
Joined: Jul 2016
Posts: 146
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memories from back in my 4wd truck days, jack up one front wheel station with 4wd engaged but engine not running. try spinning the wheel. Hopefully it won't turn. The sound you describe makes me think of torque wind-up which had a tendency to snap driveshafts in the axle casings.
My next thought would be to remove the t/box to front axle driveshaft then attempt to engage 4wd. If the symptoms you describe remain - trouble disengaging 4wd - then that would indicate a transfer box problem rather than a front driveline problem.
My next thought would be to remove the t/box to front axle driveshaft then attempt to engage 4wd. If the symptoms you describe remain - trouble disengaging 4wd - then that would indicate a transfer box problem rather than a front driveline problem.
Thread Starter
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Mountain Pass
Joined: Jul 2016
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Okay, have some new information which leads to more questions....
I lifted each front wheel with the hubs locked and the truck in 4 high. Oddly, they had about 4 inches of rotational movement each way but held firm once the play ran out. I could see everything moving well all the way back to the rear diff where I think the slop is, is this normal?
I also moved each front wheel with it in 2 high and the opposing hub unlocked and it moves the axle through the diff smoothly without noise or drag which makes me confident that the axle shafts and diff are all in good shape.
Driving the 4x4 works, with all the symptoms I noticed earlier. It moves between all the gearing just fine from 2 high when stopped and in neutral. Drive just a bit in 4 high and it takes a hard kick to get it back into another position. its very rough in 4 high until about 15 MPH. I can move it from 4 high to 2 high easily if the truck is rolling ever so slightly with the trans engaged so the TC is moving slightly.
My guess is bruised and battered but not broken TC. Next question, Rebuild or replace? I guess that all comes down to how to gears look?
Thanks again for the help guys!
I lifted each front wheel with the hubs locked and the truck in 4 high. Oddly, they had about 4 inches of rotational movement each way but held firm once the play ran out. I could see everything moving well all the way back to the rear diff where I think the slop is, is this normal?
I also moved each front wheel with it in 2 high and the opposing hub unlocked and it moves the axle through the diff smoothly without noise or drag which makes me confident that the axle shafts and diff are all in good shape.
Driving the 4x4 works, with all the symptoms I noticed earlier. It moves between all the gearing just fine from 2 high when stopped and in neutral. Drive just a bit in 4 high and it takes a hard kick to get it back into another position. its very rough in 4 high until about 15 MPH. I can move it from 4 high to 2 high easily if the truck is rolling ever so slightly with the trans engaged so the TC is moving slightly.
My guess is bruised and battered but not broken TC. Next question, Rebuild or replace? I guess that all comes down to how to gears look?
Thanks again for the help guys!
Senior User
Joined: Aug 2017
Posts: 156
Likes: 1
From: Farmville, NC
That does sound to me like the front drive-train is sound. My diagnosis would be a fault in the transfer case too. I've not even looked inside this transfer case but others seem to think it's a solid unit. As a final check before getting involved in the TC I'd carry out the same checks on the rear drive-train.
As to what torque wind-up is? (not sure if this is also axle wrap as mentioned above)
https://www.freeasestudyguides.com/d...in-windup.html
The front wheels when cornering (being the steering wheels) have to follow a bigger arc than the rear wheels to get from point a to point b so they have to rotate faster to cover the same straight line distance in the same time.
I like the picture on this one but the description on the previous one.
Transmission Wind-Up
As to what torque wind-up is? (not sure if this is also axle wrap as mentioned above)
https://www.freeasestudyguides.com/d...in-windup.html
The front wheels when cornering (being the steering wheels) have to follow a bigger arc than the rear wheels to get from point a to point b so they have to rotate faster to cover the same straight line distance in the same time.
I like the picture on this one but the description on the previous one.
Transmission Wind-Up
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