c4 wont go into any gear unless i rev it to 2500 rpms

[brandonhalfmann]

i have a 1990 ranger i put a 302 in with a c4 tranny i don't know why but it wont go into ANY gear unless i rev the motor to 2500 rpms and then it seem to go into gear and will go back out if i let off the gas...any ideas what it could be...bad vacuum? or transmission vacuum module?

 

[kimcrwbr1]

Check for manifold vacuum at the modulator. Is the tranny full of oil? Is the diaphram in the modulator good, Normally it is a cracked loose vacuum line, if vacuum is good replace the modulator if that dont work then maybe a dirty valve body. Did you change the oil and filter when you installed the tranny?

 

[kimcrwbr1]

If you do a oil change and filter check to see if the torque converter has a drain hole, drain the torque converter and get a can of oil cooler flush and flush out the oil coolerlines at the tranny and blow them out good with air.

 

[Tedybear]

Sounds more like severe low pressure. Is this a recent rebuild, used install, etc?....

I'd be more interested in putting on an transmission oil pressure gauge on the external port and seeing what's going on. Sounds more like a bad pump or severely clogged up filter. If it won't go into reverse or drive until you boost it to 2500 rpm? Sounds serious, and the modulator valve being bad will not prevent it from going into first gear or reverse. If it's got the correct level of fluid, it should at least engage first or reverse. If it doesn't? Pump or filter obstruction.

S-

 

[kimcrwbr1]

Agreed after reading it a couple times. I would drop the pan and give it a good visual look for metal shavings in the pan, large pieces not good. Take a large screwdriver and pry back and fourth looking for end play on the intermediate drum any more than about .042 thousandths it`s due for a rebuild. .008 to .042 is spec.

 

[brandonhalfmann]

i got the truck with the motor out of it and the transmission was already mounted in the truck i assumed the converter was full of fluid since it was leaking and forgot to put oil into it before i bolted up my motor...it could just be low on fluid would that make it do that

 

[kimcrwbr1]

Yup Run the engine and check the oil level with the tranny in neutral. It`s important not to over fill so add fluid 1/4 quart at a time until you see it in the cross pattern on the dipstick and let it come up to temp by driving it around. That would be the easy fix yes.

 

[Tedybear]

Yup Run the engine and check the oil level with the tranny in neutral. It`s important not to over fill so add fluid 1/4 quart at a time until you see it in the cross pattern on the dipstick and let it come up to temp by driving it around. That would be the easy fix yes.

I hope it is in fact that easy. That's actually a fairly good transmission that is pretty stout in most cases.

S-