FIRST DRIVE AFTER ENGINE REBUILD AND TRANS NOT WORKING

[rfiset]

Hi all. This is my second post today but another topic. The resto shop took car out for first drive after my '73 Vert had the 351 4V rebuilt. The engine is running great but the tranny does not shift correctly. It got stuck in third and then stuck in reverse. The transmission worked fine before the car went in. It sat out of the car for 6 months during the engine rebuild. The shop has checked everything they can but can't seem to find the reason and said it will need to be removed, examined and rebuilt. ANY IDEAS what may be wrong? Probably a long list. I really like the shop and they are frustrated also. Was planning to drive it home but not yet unfortunately. It does not sound like something simple............ Thanks 7173 fans!

 

[Idaho Chris]

C-6 or FMX?

Hard to understand why it would work fine and after R&R would need rebuilding. Makes me think something external and simple. Shifter not hooked up correctly, fluid, trans cooler lines, vacuum line problems, etc.

How many miles on the tranny?

 

[71coop]

When I swapped transmissions (ragged-out FMX for a rebuilt FMX) I had to tinker with the shifter rod adjustment to get it to shift from P through D1 correctly. It's been a while, but it seems like I had to get the shifter and rod relationship in in exactly the right spot to correctly move through the gears.

 

[detritusmaximus]

When you say it is stuck, do you mean the shifter won't move or it stays in a particular gear even after moving the selector?

If it's the latter...something in the valve body? Is there a valve that is related to both reverse and third?

 

[Don C]

Start with the simple, fluid level and shifter adjustment.
Make sure the fluid level is correct and checked after it has run for a while to make sure all of the air is out of the system. Even though they didn't remove the torque converter from the transmission it may have drained out into the pan, which cause a low fluid level after the torque converter fills back up. Another possibility is that someone filled it to the full line when it was cold, which results in it being overfull, which may cause foaming and air in the system. When it is cold after running a few minutes the fluid should just show on the bottom of the dip stick, with the engine running and transmission in park.
Maek sure they have the correct procedure for adjusting the shifter linkage, someone may just be doing it by guess and feel.
Oftentimes the low man on the totem pole is assigned the final few "easy" items and doesn't get them all right. I have known of people that should know better not checking the fluid level with the engine running.

 

[turtle5353]

Hopefully they didn’t jam up the converter when installing motor. If they didn’t seat the converter completely and pulled trans up tight to the block with the bolts, they may have smoked the pump.

 

[turtle5353]

Also check vacuum line to modulator and modulator itself.

 

[Sheriff41]

I'm with @Idaho Chris - which transmission are we dealing with? Being reverse and third sounds like a shifter issue on a manual box

 

[rfiset]

Thanks to everyone who responded! It is a C6 trans with supposedly less than 20,000 miles but may be 120,000. Title history doesn't go back far enough to know for sure. The shop is going to contact a trans specialist to go over it. Would love for him to find something simple. Going over to the shop after the New Year with a video and diagram I made of the vac lines before they pulled the motor. Maybe something will show up that might help them figure it out. Will update post when I hear more. They assured me they checked everything.....but sometimes one can overlook the obvious..... Many thanks for your ideas.

 

[machattack]

Hopefully they didn’t jam up the converter when installing motor. If they didn’t seat the converter completely and pulled trans up tight to the block with the bolts, they may have smoked the pump.

This happened to me on the new engine and Tranny rebuild. All parts were new but the new convertor from Oriely auto bolted up a tiny smidgion off. Put it into a bind and caused issues. Had to pull the tranny and relieve the bolt pattern holes out some and Wa-La it all worked great and I have 6k miles on it now.

 

[cjstaci]

I agree it doesn’t sound like a simple fix. My thought is fresh fluid in a used transmission can sometimes wash debris loose causing clogged passages. If you’re not sure of how many miles are on the transmission, I think you would be better off going through it. It’s good insurance and piece of mind.

 

[rfiset]

Thanks cjstaci. After having the engine rebuilt it would be foolish not to go thru it completely. Just wasn't planning to spend more $$$ than I already have. Peace of mind worth it like you said. Stuff happens.

 

[cjstaci]

2024 will have your car running, drive it like it’s 1973. Happy new years!

 

[72MustangSprint]

Thanks to everyone who responded! It is a C6 trans with supposedly less than 20,000 miles but may be 120,000. Title history doesn't go back far enough to know for sure. The shop is going to contact a trans specialist to go over it. Would love for him to find something simple. Going over to the shop after the New Year with a video and diagram I made of the vac lines before they pulled the motor. Maybe something will show up that might help them figure it out. Will update post when I hear more. They assured me they checked everything.....but sometimes one can overlook the obvious..... Many thanks for your ideas.

Makes me think the shop jammed it up or didn’t hook up correctly. Second thought some debris shook loose and caused a problem internal of transmission

 

[cjstaci]

Just following up, did you get the problem fixed and if so, what was wrong?

 

[rfiset]

cjstaci, the trans is working again quite well. I was able to get it home and in my garage before all the snow arrived! Thankfully! The shop checked the kickdown lever and it was functioning properly. They replaced the vac modulator checked the vac hoses and vacuum and still no improvement. Turns out the culprit was fine debris clogging up the valves in both the governor and valve body. Likely stirred up removing the transmission and replacing the fluids. It also sat for 6 months while the engine was rebuilt. The shop removed the tailshaft and found one of the valves was sticking in the governor and cleaned that and got it working correctly both reverse and forward but still not upshifting/downshifting correctly. They then dropped the trans pan and found fine debris in the bottom of thepan and the main regulator valve sleeve stuck. They cleaned the entire valve body and got all the valves working, ran the trans fluid thru a filter and put it all back together. May very well eventually need a full rebuild someday. Glad to have it back! Thanks for your interest. Rick

 

[cjstaci]

Glad it worked out well for you.

 

[rcadd1ct]

cjstaci, the trans is working again quite well. I was able to get it home and in my garage before all the snow arrived! Thankfully! The shop checked the kickdown lever and it was functioning properly. They replaced the vac modulator checked the vac hoses and vacuum and still no improvement. Turns out the culprit was fine debris clogging up the valves in both the governor and valve body. Likely stirred up removing the transmission and replacing the fluids. It also sat for 6 months while the engine was rebuilt. The shop removed the tailshaft and found one of the valves was sticking in the governor and cleaned that and got it working correctly both reverse and forward but still not upshifting/downshifting correctly. They then dropped the trans pan and found fine debris in the bottom of thepan and the main regulator valve sleeve stuck. They cleaned the entire valve body and got all the valves working, ran the trans fluid thru a filter and put it all back together. May very well eventually need a full rebuild someday. Glad to have it back! Thanks for your interest. Rick

Good news!

Did you by chance have the radiator flushed/swapped after the trans rebuild?

Junk can get in the cooler from the previous trans and fresh fluid will deposit it into the freshly rebuilt transmission.

Sounding like that might have happened.

Good luck with your project. Hopefully the weather will break and you can drive it some.

 

[basstrix]

Thanks for the follow-up. Glad you got it working.

 

[rfiset]

rcadd1ct, The original functioning non-rebuilt trans was reinstalled after the engine rebuild. Never had the radiator trans cooler flushed but it was a relatively new radiator and they replaced the trans fluid twice. Still could of come from radiator trans cooler tho. Never considered that but makes sense as all the trans fluid goes thru the cooler eventually. They got a lot of fine metal out of the panand valve body so hopefully that was most of it! Thanks for your input. Rick