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Discussion Starter · #1 ·
I drive a 1997 T100 SR5 and the other day I had my rear driver side wheel fall off of the truck for no good reason other than my lugs failing. I was going about 15 mph when it came off and lost the wheel and the rear brake drum and dragged about 10 yards. I just got the truck back this morning after having full brakes on both sides as well as axle seals and wheel bearings and now the rear end is making a pretty loud humming noise. When I parked the truck in my driveway this morning it slid/rolled down my driveway. It looked like the front wheels didnt roll but both back ones did. Not sure what is going on with that.
The 4x4 on the truck has been hit or miss for a while but just today finally quit. It had been making a clicking sound under the dash when I would try to engage and would not engage unless I tried it right after a cold start. A mechanic showed me a trick of pulling off the vacuum hose and then trowing it in 4 and putting the hose back on and that worked for a while and isnt working anymore. There is also no more clicking sound from inside but when im outside by the hoses i can hear a different clicking. the hoses seem to have good suction still so I'm wondering if its the actuator or possibly the ADD switch in the dash.
Any ideas as to what could be causing my issues?
 

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1998 T100 SR5 2WD
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Welcome to the forums! :)

Have you tried vacuum testing the switches to see if they will pass the vacuum test? Have you inspected yer vacuum lines to make sure they haven't broken down as rubber will age over time. You can use a vacuum pump on the lines and see if it holds vacuum and if the actuator moves into the proper position. BTW, have you been cycling yer 4WD system monthly to make sure it's working properly? ;)

Harbor Freight has vacuum pumps that would work. ;)

Did the shop who did the rear axle repair perform a test on the differential by pulling and inspecting it? It may have taken a hit and it's letting you know with the sounds/vibrations yer gitting. ;)
 

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1998 T100 SR5 2WD
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A simple vacuum gauge can also help you perform diagnostics on yer issue. Here's a video from the Eric O over at South Main Auto performing diagnostics on a Ford 4WD vacuum hub system. ;)

Vacuum gauge over at Harbor Freight. ;)
 

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Discussion Starter · #4 ·
Welcome to the forums! :)

Have you tried vacuum testing the switches to see if they will pass the vacuum test? Have you inspected yer vacuum lines to make sure they haven't broken down as rubber will age over time. You can use a vacuum pump on the lines and see if it holds vacuum and if the actuator moves into the proper position. BTW, have you been cycling yer 4WD system monthly to make sure it's working properly? ;)

Harbor Freight has vacuum pumps that would work. ;)

Did the shop who did the rear axle repair perform a test on the differential by pulling and inspecting it? It may have taken a hit and it's letting you know with the sounds/vibrations yer gitting. ;)
Could the diff also be the reason that park didn’t fully engage? I really want to avoid bringing it back to the same shop as they have not been helpful or done quality repairs
 

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1998 T100 SR5 2WD
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Could the diff also be the reason that park didn’t fully engage? I really want to avoid bringing it back to the same shop as they have not been helpful or done quality repairs
Has yer transmission ever not locked in Park before the incident? Does the "P" light up when you shift it into Park? Can you hear the parking pawl clicking/locking when you shift into Park? It's possible that the linkage might need some adjustment. Do you have any aftermarket body/suspension modifications installed like a body lift? ;)
 

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1998 T100 SR5 2WD
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The other issue could be that the parking pawl (inside the transmission) may be damaged. Was the transmission in Park when it was towed on to the flatbed tow truck? If so, there stands a good chance that it may have been damaged. ;)
 

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Discussion Starter · #7 ·
Has yer transmission ever not locked in Park before the incident? Does the "P" light up when you shift it into Park? Can you hear the parking pawl clicking/locking when you shift into Park? It's possible that the linkage might need some adjustment. Do you have any aftermarket body/suspension modifications installed like a body lift? ;)
Yeah it has and when it was super cold last winter it wouldn’t engage and the light wouldn’t come on and I would just take it out and put it back in again and it would be fine. But also it would lock up and I couldnt get it out of park till the truck had warmed up. No lift or body mods. The truck was in neutral when it got towed
 

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1998 T100 SR5 2WD
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Chances are that you can adjust the transmission linkage a little bit at a time at the firewall and it should be able to engage the parking pawl. ;)
 

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Jack up the back axle and try to spin it in neutral, with the parking brake engaged.
Jack up the front wheels in 4x4. You should have the front driveshaft spinning.
If you have enough jacks get the front and rear wheels off the ground and put it in 4x4 and spin the wheels.
Let us know what happens in each situation.
 

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This is your driverside inner fender. See those 2 vacuum solenoids in the middle. One red, one blue.
Switch the vacuum hoses going to each one. Hoses are color coded red and blue striped. Put red stripe on blue solenoid, and blue on red. This bypasses all the electronics in the ADD system and shifts the ring collar in your front diff, locking your your cv axles together. If you switch the vacuum hoses and put the tcase shifter in 4x4, you should be in 4x4. You will not have a 4wd dash indicator. If your 4x4 is not working when you do this, you have a mechanical problem in your T case or front diff.
If you do go into 4x4 in this position, you have an electronic problem.

The back axle may be a somewhat seperate problem. Jack the back up first. Spin one wheel, the other should spin freely in the opposite direction. They should both stop when you pull the ebrake. Listen for any grinding in the dif. A lazy mechanic might not want to open your dif up even if they saw something wrong
 
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Sorry for being repetitive. I just reread your first post and saw you already tried the hose switcheroo. If thats not working and you are getting vacuum from one of the tubes, i think its a diff or tcase issue.
Your on an auto transmission?
 

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Discussion Starter · #12 ·
Sorry for being repetitive. I just reread your first post and saw you already tried the hose switcheroo. If thats not working and you are getting vacuum from one of the tubes, i think its a diff or tcase issue.
Your on an auto transmission?
yeah im on an auto trans. Im wondering if my ADD switch may have gone out? I used to hear a clicking sound under the steering wheel when i would try and put it in and now i dont hear anything. There is a pretty significant hum coming from the center or back end of the truck.
 

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1998 T100 SR5 2WD
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yeah im on an auto trans. Im wondering if my ADD switch may have gone out? I used to hear a clicking sound under the steering wheel when i would try and put it in and now i dont hear anything. There is a pretty significant hum coming from the center or back end of the truck.
You could disconnect the driveshaft and see if the hum still exists or not. Yer gonna need to narrow down where it's coming from. Could be the driveshaft, center support bearing, or differential. ;)
 
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