Transmission questions

[carter262]

Stock 1987 M1028

Last week the transmission suddenly quit shifting. There was no slipping, noises, or any type of warning. It was running fine, I stopped at a stop light once it turned green I started to move on and it would no longer shift out of first.

Has anyone ever had this happen?

What I have checked.

Vacuum pump had stopped. It has been replaced and now has vacuum. Still would not shift.

Checked the vacuum lines. All were good.

Replaced the modulator. Still would not shift.

All fluids levels are good.

Since there was no warning signs, I don't think its the transmission itself, but I could be wrong.

What else can I do or check before I have to pull the transmission?
Is there a way to tell if it is the transmission without pulling it?

 

[NDT]

Put a vacuum gauge at the modulator, vacuum should replicate what a gas engine would be, 25 inches at idle and 5 at wide open throttle. If no vacuum the issue might be the valve on the injection pump, called the VRV. If you have plenty of vacuum, and a new modulator, the problem is internal.

 

[90Jimmy]

Will it shift manually? Check the valve that NDT in referencing, not sure its a valve but they dry rot... that part is also adjustable. It controls how early or late shifts happen. I will find a pic of what I'm talking about.

 

[Matt5]

Should still shift, I had a truck with the line flat out not connected, she reved... but she went though all the gears...

Best thing to do, pull the line at the tranny, check for vac... if none work your way back... I mean you could also start at the pump...

 

[dependable]

I'd check the shift linkage.

 

[Tinstar]

When was the last time the trans filter was changed?
Restricted filter won’t help anything.

I know you said the fluid level was good but it has to flow freely through the filter.

 

[socalsrt]

Sounds like the transmission governor gear is stripped out. On the passenger side of the transmission there is a metal four bolt cover about 4 inches by 4 inches. Take the plate off and pull the governor out. Inspect the plastic gear. Super easy fix, but the only place I could find a replacement was ebay. Same thing was wrong with mine when I got it from the military.....

 

[CBrinker]

Sounds like the transmission governor gear is stripped out. On the passenger side of the transmission there is a metal four bolt cover about 4 inches by 4 inches. Take the plate off and pull the governor out. Inspect the plastic gear. Super easy fix, but the only place I could find a replacement was ebay. Same thing was wrong with mine when I got it from the military.....

I had this exact thing happen on my m1008 a couple months ago. Was driving perfectly, then left from a light and all of a sudden wouldn’t shift out of 1st. The plastic gear on the governer was stripped out flat. Installed a new plastic gear on the governer and then it was good as new.

 

[carter262]

Okay back up and running. So had two problems. The vacuum pump was out and the governor gear was bad too. Luckily I had a spare for both of them.

Now I need to repair the old ones so that I have spares again. Does any one have the part number for the replacement gear?

 

[CBrinker]

Okay back up and running. So had two problems. The vacuum pump was out and the governor gear was bad too. Luckily I had a spare for both of them.

Now I need to repair the old ones so that I have spares again. Does any one have the part number for the replacement gear?

I have the part number for the gear i believe. I will check and post it later tonight when i get home

 

[carter262]

I have the part number for the gear i believe. I will check and post it later tonight when i get home

Any luck finding that part number?

 

[CBrinker]

Any luck finding that part number?

I completely forgot to look, sorry. I'll check today

 

[CBrinker]

I couldn’t find the number for the one I bought because it was aftermarket, but the gm number I found is [FONT=&quot]3914F[/FONT]

 

[porkysplace]

Here is the link to the kit I used on ebay/QUOTE]

Screenshot with part numbers.

 

[doghead]

https://www.google.com/search?q=th400+governor+gear&ie=&oe=


https://www.transmissionpartsusa.com/TH400_Transmission_governor_gear_kit_p/400-000046327.htm

 

[carter262]

Thanks for the help and information. As always you guys rock!!