Automatic Transmission Problem- downshifting at 3rd

[Ryan S.]

As you may know, I have been having a transmission issue. So transmission was rebuilt with a kit, replaced torque converter with a brand new one, added a DPI transmission cooling kit, upgraded governor computer from DMC, and while engine was out, also replaced vacuum hoses, spark plug wires, distributor, oxygen sensor.

Reassembled and test drove last night, car drove fine on 1st and 2nd gear but at 3rd, it downshifted and car slowed down. It kept doing the same, 1st, 2nd, and 3rd then it started to slow down. Just like if you were downshifting from 4th gear to 3rd gear in manual. Hope that makes sense.:hmm: Not wanting to damage anything, didn't try to go any faster beyond that point.

Other factors: Car was sitting in my garage for over 3 months. Battery was dead so I had to jump start. I may need a new battery.

I would greatly appreciate any feedbacks or suggestions.
thank you

[AugustneverEnds]

Low power can definitely cause strange behavior with the auto transmission so battery replacement is a good place to start. Is the rest of the charging system working ok? Also did you check the fuse for the auto trans?

[AugustneverEnds]

It's fuse 13 BTW. 10 amp I think.

[DMCMW Dave]

While driving, when it should go to 3rd gear pull fuse 13. It should go into third and stay there until you put the fuse back in. If it does, there is something wrong with the governor (new I know but stuff happens, and it's possible to install it incorrectly if the solenoid harness was removed). If that is what you see call me and I'll walk you through some function tests. We test them on a car before we ship the unit, but I don't recall if yours came in fully wired or not.

The way you describe it, it's starting out in first, going to second, and them dropping back to first. I can't envision how an incorrectly wired governor could do that, but the "yank the fuse" test is conclusive.

If it does not go into third with the fuse out, you have an internal hydraulic issue, meaning the rebuilder screwed up and gets to do it over again. But before you pull it have him run a line pressure test in the car as well.

[David T]

While driving, when it should go to 3rd gear pull fuse 13. It should go into third and stay there until you put the fuse back in. If it does, there is something wrong with the governor (new I know but stuff happens, and it's possible to install it incorrectly if the solenoid harness was removed). If that is what you see call me and I'll walk you through some function tests. We test them on a car before we ship the unit, but I don't recall if yours came in fully wired or not.

The way you describe it, it's starting out in first, going to second, and them dropping back to first. I can't envision how an incorrectly wired governor could do that, but the "yank the fuse" test is conclusive.

If it does not go into third with the fuse out, you have an internal hydraulic issue, meaning the rebuilder screwed up and gets to do it over again. But before you pull it have him run a line pressure test in the car as well.

Agree with everything here but would add to check all of the external adjustments and make sure the fluid level is correct in the transmission AND the final drive before you do anymore tests.

[Ryan S.]

Thank you for suggestions,
Installed a new battery.
I had a fuse switch so I plug a switch into fuse 13 and I just performed the fuse test. It didn't go into 3rd when I turn off the fuse 13 from 2nd gear. Instead, it felt like a power loss or nothing was happening with gas pedal pressed.
When I turn off the fuse 13, at the start, car wouldn't move, is it normal?
After driving, car had a slight burning smell (plastic like). Not sure where it was coming from.

[David T]

Thank you for suggestions,
Installed a new battery.
I had a fuse switch so I plug a switch into fuse 13 and I just performed the fuse test. It didn't go into 3rd when I turn off the fuse 13 from 2nd gear. Instead, it felt like a power loss or nothing was happening with gas pedal pressed.
When I turn off the fuse 13, at the start, car wouldn't move, is it normal?
After driving, car had a slight burning smell (plastic like). Not sure where it was coming from.

Confirm the gearshift is actually getting the valve body into the 3rd gear detent. If you can't get 3rd at all you probably have a problem with the roller clutch or C1 which will require the trans to come out. If it won't move at all with no #13 fuse the problem is internal, you do not have 3rd gear. Refer to G:04:03-:04

[Ryan S.]

We are praying that we don't have to take it apart again. I tried the fuse 13 test again but it doesn't look good.

This morning, I have been testing using a switch to fuse #13 to figure out which gear this transmission is engaging actually when it goes to 3rd. What I found out is....it is not Reverse, 1st, or 3rd. I am not sure what it is????
Let's say... if for some reason, 3rd gear is engaging or becomes the 1st gear, I should be able to move my car effortlessly from a stop with fuse 13 off but car struggles to move with gas paddle pressed. It sort of moves forward very very slowly and car shakes like it has no power.


From 2nd gear, right before it goes to 3rd, if I turn off the fuse 13 then car starts to slow down. It feels like it is going to a lower gear but without any power when I press gas. It feels like downshifting but not a true downshifting. Just slows down to a near stop even with gas.


With fuse 13 on, at 3rd gear, car starts to slow down and eventually the 2nd gear engages back on and car speeds up and slows down at 3rd and so on...it repeats the cycle.




So these tests confirm that 3rd gear is not going into 1st gear.

Hope Josh will give us some good news or guidance on this issue. It is getting pretty depressing these days as I just totaled my Lotus in an accident and D is still down. uggg...:cry:








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[DMCMW Dave]

[SIZE=2][FONT=arial]We are praying that we don't have to take it apart again. I tried the fuse 13 test again but it doesn't look good.

[FONT=arial][SIZE=2]So these tests confirm that 3rd gear is not going into 1st gear.



My guess is that when it's supposed to be in third, it's in second and third (or any other pair of speeds) at the same time. That would explain the shuddering/power loss rather than just the feel of being in too low gear. It's still an internal issue.

[Ryan S.]

Thanks Dave. Always appreciate your helpful advices.

[Delorean Industries]

Its definitely internal related. I would check the valve body first prior to pull the hydraulic unit. I second the two at one time theory due to a hydraulic fault.

[David T]

Its definitely internal related. I would check the valve body first prior to pull the hydraulic unit. I second the two at one time theory due to a hydraulic fault.

To confirm what gear you are in you can refer to the RPM v MPH chart for the automatic. Otherwise if the shift computer is working and commanding the valve body you can use a light box to see what gear. You should have the chart anyway just in case you lose the speedometer you can judge your speed with your tach. The pull the #13 fuse test is supposed to force the transmission into 3rd gear. Not a great way to drive but it is the "limp home " mode and will get you home, just take it easy from a standing start. If you get no forward motion when you pull #13 you have NO 3rd gear and it will be an internal problem, nothing to do with the shift computer. This assumes you have the proper level of fluid in the transmission and good line pressure.

[Ryan S.]

Thanks guys. I hope Clint can sort this out for me by next weekend.