NP435 GRINDING WHILE IN GEAR

[robv2346]

I have a 1984 F250 XL 4x4 150,000 miles (u8500) 4.9 NP435 Np205 original owner. Last year changed to synthetic 75w90. I have never taken on highway just putter around town. I went on an extender highway drive and about 10 minutes in in 4th gear i heared a grinding noise like it popped out of gear. I clutched and took out and went back into 4th fine. Happened again on way back after about 5 miles, got off highway and then when in 3rd did it again on off ramp. Took back roads home no problem. It seems to only happen after a while when warm. Happened in reverse once other day. Not sure if someone has a diagnosis. I have a lead on an NP435 from 85 f150 in junkyard for $200 bucks. Not sure if i should roll dice and swap. I am wondering if this junkyard one is the same. I didnt get a tag on pick.

[Gary Lewis]

First, please make sure you go to the New Members Start Here folder, as asked in the email you were sent, read the guidelines, and then start a new thread in that folder to introduce yourself. It is important that you understand the guidelines as all members are bound by them.

As for your transmission, is it just a noise or do you seemingly go into neutral? How does the transmission shift?

And, have you checked to see if the transfer case might have slipped out of gear?

[robv2346]

First, please make sure you go to the New Members Start Here folder, as asked in the email you were sent, read the guidelines, and then start a new thread in that folder to introduce yourself. It is important that you understand the guidelines as all members are bound by them.As for your transmission, is it just a noise or do you seemingly go into neutral? How does the transmission shift?And, have you checked to see if the transfer case might have slipped out of gear?

Ok will do that..  It shifts fine,  I occasionally lately just here a grinding noise while in gear. Happened in reverse once too.   I immediately clutch and take out of gear and then i am able to go into gear and its fine..  I thought that the transfer case is pretty much direct drive to rear, i didnt think of the TC.   I had the TC rebuilt about 15-20 years ago.  There are currently no leaks. 

 

Thanks for your help.

 

 

Rob Voorhis

Paramus NJ

 

 

On Tue, Jan 7, 2020 at 6:58 PM Gary Lewis [via Bullnose Enthusiasts] <redacted_email_address> wrote:

 

 

 

[Gary Lewis]

I was waiting to respond because I thought you said you'd check the transfer case and report back, but now that I look you didn't really say that. But, you should check it out. See if going into 4hi makes a difference. Check to see that it appears to be shifting correctly.

So, on the grinding, did it seem to start right after you changed out the fluid in the transmission. I always like to go back to whatever was done immediately prior to the problem cropping up, so have you checked the level to make sure the transmission is full? Did anything odd come out with the old fluid, like pieces?

[robv2346]

I was waiting to respond because I thought you said you'd check the transfer case and report back, but now that I look you didn't really say that. But, you should check it out. See if going into 4hi makes a difference. Check to see that it appears to be shifting correctly.

So, on the grinding, did it seem to start right after you changed out the fluid in the transmission. I always like to go back to whatever was done immediately prior to the problem cropping up, so have you checked the level to make sure the transmission is full? Did anything odd come out with the old fluid, like pieces?

To clarify the subject line, i have a NP435 / NP205 combo. No lift. It shifts through gears fine. The first time it happened was on highway trip at 55 mph in 4th. Then when i got off the highway and downshifted on ramp to 3rd it happened again. If i baby the truck meaning dont go over 40mph and dont downshift to decelerate everything is fine. I am getting the grinding when when i downshift from 4th to 3rd and 3rd to second to go into a turn. If a take a turn and take it out of gear and then go easy into third at low rpm i get no grind. I could swear that the noise is similar to the times where the TC shifter gets knocked out of 2H in between 4H.

While typing this i discovered this video

I am going to check here first. It seems similar to the broken ring in rear output shaft starting at 1:35. This is the exact same noise i am getting. I am going to try to find that clamp.

[Gary Lewis]

To clarify the subject line, i have a NP435 / NP205 combo. No lift. It shifts through gears fine. The first time it happened was on highway trip at 55 mph in 4th. Then when i got off the highway and downshifted on ramp to 3rd it happened again. If i baby the truck meaning dont go over 40mph and dont downshift to decelerate everything is fine. I am getting the grinding when when i downshift from 4th to 3rd and 3rd to second to go into a turn. If a take a turn and take it out of gear and then go easy into third at low rpm i get no grind. I could swear that the noise is similar to the times where the TC shifter gets knocked out of 2H in between 4H.

While typing this i discovered this video

I am going to check here first. It seems similar to the broken ring in rear output shaft starting at 1:35. This is the exact same noise i am getting. I am going to try to find that clamp.

Rob - First, you shouldn't have an NP205. Instead, it should be an NP208. The 205 wasn't used in these trucks, as shown here: Documentation/Driveline/Transfer Cases and on the Applications tab.

Second, there are factory shop manual instructions on the transfer cases on that page as well, and they include diagnosis and testing which might help.

Last, I asked if you've tried 4hi on the transfer case to see if it makes the noise, but you've not answered that question. I ask because the nylon shift forks are known to wear out on the t-cases and then they don't shift into the gears properly. If yours are worn you may not be all the way into 2hi or 4hi and could cause that noise. So check out the different positions on the t-case lever and see if that makes a difference.

[robv2346]

Rob - First, you shouldn't have an NP205. Instead, it should be an NP208. The 205 wasn't used in these trucks, as shown here: Documentation/Driveline/Transfer Cases and on the Applications tab.Second, there are factory shop manual instructions on the transfer cases on that page as well, and they include diagnosis and testing which might help.Last, I asked if you've tried 4hi on the transfer case to see if it makes the noise, but you've not answered that question. I ask because the nylon shift forks are known to wear out on the t-cases and then they don't shift into the gears properly. If yours are worn you may not be all the way into 2hi or 4hi and could cause that noise. So check out the different positions on the t-case lever and see if that makes a difference.

Yes! 208f .. and yes same think in 2H and 4H. For starters I will pull rear output shaft cone and check it that ring is in tact.  Thanks will report back. 

 

On Thu, Mar 5, 2020, 9:23 AM Gary Lewis [via Bullnose Enthusiasts] <redacted_email_address> wrote:

 

 

 

 

[Gary Lewis]

You might want to look at the factory shop manual section on that page to insure a 208 has the snap ring he's talking about. On the BW1345 I just rebuilt you can't get to any snap rings w/o taking the whole transfer case apart.

[robv2346]

You might want to look at the factory shop manual section on that page to insure a 208 has the snap ring he's talking about. On the BW1345 I just rebuilt you can't get to any snap rings w/o taking the whole transfer case apart.

Still trying to diagnose this grinding, NP208 TC or the NP435 trans i have been just babying the thing and it was fine, put lately while driving easy in 3rd gear i will get the grinding noise and again if i clutch and go neutral and then back in gear at low rpm / no strain it is fine. Question: i put the transfer case in neutral and then put the trans in gear and i get a grind while release the clutch. It this normal? Does this narrow it down to the transfer case? i would pull it out and then send out for rebuild if thats the case.