Too Late shift problem

[als804]

Actually these days my shift points are seriously late.

used to(some times a little early sometime a little late)
1->2 at near 2400rpm at near 23mph
2->3 at near 2500rpm at near 40mph.

these days( can shift at the exact same speed):
1->2 at 3400rpm at 33mph
2->3 at 3200rpm at 52mph

these days shift is too late.More than 3000rpm makes me feel hard and painful!
i checked all the vacuum lines but nothing problem found out.
some dude get it connected directly between vpump and v modulator of transmission.

you guys can you notice the problem?

 

[Skinny]

Find the dude that stole the vacuum valve on your injection pump.

Sent from my SM-T380 using Tapatalk

 

[TechnoWeenie]

That Turbo 400 uses the vacuum pressure to determine shift points. The vacuum regulator is there for a reason.

Also, if the vacuum pump is hooked up directly to the modulator, you should get super early shifts.

The lines, if not replaced, are almost 40 years old at this point. Replace the lines... It's possible the lines were going bad, and the previous owner hooked it up directly to the modulator as a way to mitigate pressure loss on a leaky hose.

 

[chevymike]

I had that problem when my modulator went bad. Without vacuum working correctly, TH-400 trans will shift at the governor max RPM, which is set to 3400 on the 6.2L diesels. This is like a failsafe if the vacuum system fails while driving. It will still shift, just a max RPM.

 

[Prepper_Pig]

I have the same problem after that crazy cold snap we had back in February. I couldn't find any problems with the lines (save a worn rubber boot on the line into the modulator) so I replaced the modulator and boot but my issue was not resolved.

 

[Sganderson]

I had the same issue, changed all of my lines because they were dry rotted.. There are two sizes. You need a bigger one that fits directly onto the vacuum pump and an adapter to step it down to a smaller. I discovered someone in error had placed the lines on backwards at the vacuum valve on the injection pump (which caused my transmission to shift late) There are two ports , Remember top goes to transmission modulator and bottom goes to the pump behind the engine.

 

[als804]

somebody told the vacumm pump should make -20inchHg Vacuum pressure, but mine couln't make very very weak vacuum. thanks to this nice forum, i got found the problem that is a vacuum pump problem. see number 3 picture shows a crack on kind of rubber surface inside the vacuum pump. somebody knows who sell the repair kit?

 

[cucvrus]

Cardone Industries 64-1200 Cardone Remanufactured Vacuum Pumps | Summit Racing

Says only 2 left in stock. It is a hard item to find.

 

[ezgn]

Cardone Select 90-1008 New Vacumn Pump $73.23 at Amazon 19 left.

 

[vanaisa]

When waiting new pump, you just can connect vacuum lines together and drive. Gear changes will be wery soft and un-noticeable.

 

[als804]

When waiting new pump, you just can connect vacuum lines together and drive. Gear changes will be wery soft and un-noticeable.

oh? I am afraid to say I don’t get it. Can you explain more easily?

 

[chevymike]

When waiting new pump, you just can connect vacuum lines together and drive. Gear changes will be wery soft and un-noticeable.

Actually that does not work. If not vacuum available at the trans modulator (the part the hose plugs into on the trans), it will only shift at high RPM and very harshly. This is usually the tell tail sign you have a vacuum problem (anywhere from the pump, lines, modulator, vacuum switch).

 

[vanaisa]

Chevymike, it works great - maybe i expaining it wrong (sorry, english is not my language) but when i had problems with my weak vacuum pump, my oldtimer transmission repair guy advised to discard this vacuum thingy on IP (again, cant say what it is, in my language it is vaakumkorrektor )

And it worked great,, drove about 2000mil before got new vacuum pump.

 

[als804]

i changed the pod only which i got from nice guy
everything is perfect and shift nice. thanks