Taming Transmission Shifts

[OD Heavy Hauler]

How do you fine tune the TH400 shifts? The one in my 1008 shifts at right point I believe(1-2@ +/- 20mph then from 2-3@ +/-30mph) but it shifts like it has a super shift kit in it. If it had the power it would be barking the tires. It does it most all the time whether its warmed up or cold.

 

[Warthog]

It could be the modulator or the Vacuum Valve

The TM 9-2320-289-20 covers checking the transmission in the Troubleshooting Section.

Item #51 on page 2-55. It lead you to Section 3-21 and 3-21.1

Here is my version of adjusting the Vacuum Valve.
http://www.steelsoldiers.com/cucv/50568-cucv-throttle-vacuum-valve-adjustment.html?highlight=vacuum


Also TM 9-2320-289-34 covers troubleshooting the transmission in more detail if needed.

 

[doghead]

Warthog, just yesterday I followed your thread and adjusted mine. It now shifts just right!

Thank you for that great thread.

 

[Warthog]

Glad I could help.

 

[OD Heavy Hauler]

Is the modulator valve on the tranny adjustable and how is it done? I don't have any way right now to pull a vacumn on system to make sure it's ok or for adjustments like I saw on your post link with the mity vac tool.

 

[pidgeon]

There is a screw in the middle of the vacuum port of the transmission modulator. I pulled mine almost all the way out.

Also the vacuum valve on my truck was bad. It's fairly easy to check. Take it off and trist the orange connector that hooks up to the throttle body. Blow into it. If it doesn't change the amount of air being blown through, it's bad.

Hard trans shifting from what I've read is almost always the modulator, the lines or the vacuum valve.

 

[LanceRobson]

If you have not replaced the vacuum lines do that first. They start at the vacuum pump on the top rear of the engine. Follow them to the modulator and on to the transmission. We replace them on every CUCV we come near and have only ever had to adjust one that someone adjusted prior to our changing the hoses.

After 25+ years they are porous and the leakage will result in hard shifts or late shifts.

Lance

 

[OD Heavy Hauler]

I'll check them out 1st on my next day off before I start other adjustments or parts replacements. How much vacumn does a diesel run compared to a gasoline engine? I was told it was a lower amount. Being a newbie to these MV's with the diesels I'm going to have to crawl before I walk.

 

[doghead]

OD HH, by the last post you made, I highly recommend you download and read both the -10 and -20 Tech Manuals. They will answer all your questions and give you a picture of what your dealing with.


If you don't know what those TM's are, I recommend you go directly to the CUCV forum and start reading the wiki at the top, and work your way down.

 

[Warthog]

I'll check them out 1st on my next day off before I start other adjustments or parts replacements. How much vacumn does a diesel run compared to a gasoline engine? I was told it was a lower amount. Being a newbie to these MV's with the diesels I'm going to have to crawl before I walk.

Diesels do not produce a vacuum like a gas engine. For that reason a vacuum pump is added to the engines.

Like Doghead said, make sure you visit the CUCV Forum and check out the CUCV Wiki at the top of the Page. All the tech Manuals are linked there.

The first one you want to read is the TM 9-2320-289-10 Operators Manual. It covers everything to operate the truck One important item is the Light System. ie how to turn on the brake lights.

Then for repairs you need two manuals, TM 9-2320-289-20 and TM 9-2320-289-34. Thes manuals cover the majority of the systems on the trucks. There are corresponding parts manuals for both.

 

[dieselpony]

There is a screw in the middle of the vacuum port of the transmission modulator. I pulled mine almost all the way out.

From what I know the CUCV originally had modulators WITHOUT the adjusting screw. Can be replaced very easy though . . .

Walter

 

[OD Heavy Hauler]

Those TM's here on SS that you listed are the complete manuals (like dealer service manuals or owners manuals) that can be downloaded to my pc? While I'm at it I'm going to ask one more question. I was told by person I got truck from and an ex-soldier that alternator belt squeal is normal from these vehicles when 1st started up and not to try and tighten belts up to get it out so as to not kill alt (gen) bearings. Is Gen 1 on pass. side or driver side? Just so I'll know which is which. I want to make sure this truck runs good as I want to trade/sell this M1008 to buy a M1009 to better suit my needs.

 

[pidgeon]

From what I know the CUCV originally had modulators WITHOUT the adjusting screw. Can be replaced very easy though . . .

Walter

Correct. The old one on mine did not have it. The aftermarket one does.

 

[Warthog]

Those TM's here on SS that you listed are the complete manuals (like dealer service manuals or owners manuals) that can be downloaded to my pc? While I'm at it I'm going to ask one more question. I was told by person I got truck from and an ex-soldier that alternator belt squeal is normal from these vehicles when 1st started up and not to try and tighten belts up to get it out so as to not kill alt (gen) bearings. Is Gen 1 on pass. side or driver side? Just so I'll know which is which. I want to make sure this truck runs good as I want to trade/sell this M1008 to buy a M1009 to better suit my needs.

Yes the Tech Manuals are like the dealer service manuals, but are written for the average GI. They are in PDF format and you can download them.

If the belts are squealing means they are loose and need to be adjusted. But DO NOT over tighten as you will kill the bearings.

Gen1 iis the driver side and charges the front battery. This runs all of the truck electrical except the starter and glow plugs (on a stock system)

Gen2 is the passenger side and charges the rear battery. This alternator MUST have the "isolated ground" (search for it)

 

[OD Heavy Hauler]

I noticed yesterday evening while checking out some things the Gen 1 sheave is out of alignment with the drive sheave off front of water pump. Not sure if It will go back in line. Thats a day off project. It don't look like its that much adjustment on it. Thanks to all for the help/advice. I'm sure this site will be a great info site now and in the future

 

[Warthog]

I noticed yesterday evening while checking out some things the Gen 1 sheave is out of alignment with the drive sheave off front of water pump. Not sure if It will go back in line. Thats a day off project. It don't look like its that much adjustment on it. Thanks to all for the help/advice. I'm sure this site will be a great info site now and in the future

There is a spacer that is used on the ps pump bracket. Sometimes this spacer will go missing when the pump is replaced. It causes the pulleys to misaline.

I have some pictures at work that I will post on monday.

 

[OD Heavy Hauler]

Thanks Warthog. Something must be missing or out of place. I'll look back here Mon.

 

[IdahoPlowboy]

If you have not replaced the vacuum lines do that first. They start at the vacuum pump on the top rear of the engine. Follow them to the modulator and on to the transmission. We replace them on every CUCV we come near and have only ever had to adjust one that someone adjusted prior to our changing the hoses.

After 25+ years they are porous and the leakage will result in hard shifts or late shifts.

Lance

This was all it took to solve all my tranny problems, Thank You LanceRobson.