My 1028 is down can I get some advice PLEASE oh please all knowing one

[Ronbo]

Guys I'm not much on diesels but ok on the transmission. . My problem is: It quit shifting . I thought rut- row and started to pull it out when I saw the broken vacuum line to the Modulator. I replaced the line and still no 3rd and soft 2nd. I then put a vacuum pump on the Modulator and its ok. But I'm getting no vacuum on the Modulator . The Vacuum diaphragm thingy is pulling 20 on the gauge where it connects to a Throttle sensor thing ( no wires ) and no vacuum is pulling thru it. down to the Modulator ( yet on the same devise
So my guess is the Throttle sensor thing ( on the injection pump rt. side ) what is it ? is my thinking correct? is it adjustable like a TPS ?
also the vacuum thingy that goes where a distributor goes on a small block does it get timed? ( I wouldnt think so ) ..is 20 on the gauge ok ?
Thanks
PS while I'm asking questions , I pulled the driveshaft ( rear )out and about 1 qt drained out, do you think the seals in the adapter b/t the trans. and transfer case are bad?

Thank you again oh great ones

 

[Ronbo]

Let me reword something to save confusion .. I'm getting no vacuum thru the TPS looking thing .. but has 20 at it ( none thru it ) .. Whats it for ? Could I not just hook the vacuum line from the modulator straight to the diaphragm thing that is pulling 20 lbs of vacuum

 

[toyrunner95]

ok so its staying in first and not going to second or third. the little thing on the side of the transmission is a shift modulator. the things on the injection pump is the vacuum regulator valve. inside that "vrv" is a spring. as you push on the throttle it opens the valve. so as you let off, it closes the valve allowing the trans to shift down without slamming into gear. the shift modulator regulates what gear you should be in compared to the engine RPM. so if your foot to the wood on the gas pedal and the vrv is letting all the vacuum through but the RPM on the engine isnt high enough to maintain 3rd gear or 2nd gear the transmission will downshift. a situation of that would be going uphill.

now adversly if you are going downhill and truck vrv isnt letting vacuum through the transmission will shift into the easiest gear it can. 3rd.

my first inclination would be the shift modulator on the side of the transmission. $60 at a auto parts store. an easy change. the vrv is about $125 and it takes a 10mm shallow socket on a long extension on a 3/8 drive to replace.

if the vrv went bad the truck would just start in 3rd and not downshift. but since yours is stuck in first. i would think that the modulator is bad.

 

[Warthog]

Here is a post about the Throttle Vacuum Valve

http://www.steelsoldiers.com/showthread.php?50568-CUCV-Throttle-Vacuum-Valve-Adjustment

The TM has a troubleshooting section for the transmission.

You have to have a good vacuum, good rubber with no leaks, a Throttle valve that send the correct signal to the modulator, a non-sticking modulator, AND a non-sticking/non-stripped governor on the other side of the tranny.

 

[Ronbo]

It will shift into 2nd ( softly ) no 3rd or only for a second or two.. I changed the modulator and no difference and removed the 4 bolts on the gov. on the trans and the gear is fine. I'm just not getting vacuum to the trams Modulator but I am getting vacuum to the vrv thingy just not thru the rubber T fitting on the vrv vacuum connection .

 

[Ronbo]

Thanks Toyrunner 95 and Thanks again Warthog you always seem to step up to the plate when someone needs advise . I am grateful.

 

[Ronbo]

I just got the new vrv and applied 20 " and it wont hold any vacuum .. 0. is it bad or am I missing something

 

[doghead]

That is normal.

Put it on and adjust it and see what you get.

 

[Ronbo]

Hey Dog I put it on But I cant get it to pull 20" of Vac. so I tightened the vrv down ( just centering it ) and the trans will shift but real soft. but it does go in all gears . Maybe I can adjust it and have it shift a little later and harder..
I really need it running so I can get back to work ( I use my truck for construction) and in a few weeks take the trans out an replace the flywheel , seals , etc all at once.. Is there a seal or two B/T the trans and transfer case? ( in the adapter housing? ) and does anyone use something a little beefier than trans fluid in the 208? Thanks again..

 

[toyrunner95]

when my vrv went out it stayed in second and wouldent go either way. if you really need it working, connect the two lines that go into the VRV directly together, that should give you 3rd all the time. but dont pull any steep hills.

i adjusted my vrv so it shifts fairly soft. i didnt like it to slam into gear. i believe its better for the syncros. but what do i know.

 

[Ronbo]

Well I replaced the modulator with another( 2 ) and vacuum checked it and all is good . I replaced the vacuum hoses and set the VRV in every position possible and it does shift all 3 gears but sure is soft and the position of the VRV doesnt change the shift at all. So is the VRV supposed to hold vacuum if one end is sealed off? maybe mine is half bad . The VRV is my main concern due to as soon as I can get a new flywheel and a shift kit I'm pulling the trans out for an overhaul .. I finally got the new king pins and springs for a 6 in lift. I guess brake lines are needed too.. Thanks for any advise gentlemen

 

[Skinny]

Check to make sure you don't have the steel line chaffing through somewhere. If you are trying to dial a shift characterisitc, being slightly to the harder side is better than the softer side. I doubt a TH400 in this application will break any internal parts during a slightly hard shift but any slippage will burn clutches. So if you have a choice...slightly harder is better. No synchros in an auto trans, you can't hurt it. You can though explode or chip planetaries and shells if too rough.

You may want to pull the governor and check the gear and weights. Shift points are always a battle between governor pressure (vehicle speed) and throttle pressure (vrv vacuum) in a non-electronic trans.