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Discussion Starter #1
OK, here is my problem. I have a TH350. Last week the transmission functioned perfectly. It is still very new - it only has about 300 miles on it. Yesterday, I was on the highway, and the car was driving great, then it dropped down into second. I put it into neutral, then back into drive, and it went into 3rd gear again. The problem continued. It would stay in third for a while, then drop down into 2nd. So, I brought it home, and I check the fluid level. It was fine. I put in another quart anyway, just to make sure it was not a low fluid problem. That did not fix it. I have not messed with the kick down cable. It is new, and still in good condition. The adjustable modulator is new, still in good condition. I am sure the shifter is adjusted correctly - it goes into 1st gear just fine. When it is in neutral, the car does not move at all, then when I throw it into drive, the car wants to move. It feels like only air is in the converter - but, if that were true, the car would not work in 1st, right? I have a pretty radical cam, but the transmission used to work just fine, and I have enough vacuum to run power brakes pretty well.
I read around on the forum, and other articles suggest that it could be the filter. My question is, how would the filter get clogged up so soon? the transmission is new.
Also, I want to install a B&M shift improver kit - could that fix the problem?

thanks in advance for the help -Ed
 

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A shift improver kit will not fix a damaged tranny , unless the problem is in t he valve body. Then the problem may be fixed during the kit install.

You need to make sure the vacuum to the modulator is correct for shifting to happen. The vacuum feed should be from full manifold hook up and not Tee'd into some thing else


I really do not understand the comment about " feeling like air in the converter" . Does it feel like car does not want to move or a high stall converter in action or ?
 

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Discussion Starter #3
clarification on the problem

Ok, I will clarify on what I mean by 'air in the converter'. I get in the car. In park, normal, everything is fine. I will put it into drive, and the car, at 3000 rpm, will have enough power to roll forward about a 1/2". That is what I mean by air in the converter. Perhaps it is the clutch disks not engaging. I don't know. But, continuing on, if I shift down into first, the car moves great!

I know the vacuum is good, because the transmission used to work just fine - last week. I did not change any vaccuum settings, and all the lines are hooked up. It is hooked up to the single vacuum port on the holly street dominator intake - it is the only thing attached.

I am just not sure what the problem is. I am going to put a new filter in tomorrow, the B&M shift improver kit for street/strip, and new fluid. Hopefully that will fix it. If that is not it, then I really don't know. Thanks -Ed
 
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Since your saying that you can manually downshift into 1st and it goes right, it sounds like you have a problem in the governor or possibly in the valvebody. Check the fluid level with the engine at operating temp. If the fliud level is correct and the fluid is not dark or have a burnt smell, check the governor to make sure the valve isn't stuck or the gear chewed up.

Changing the fluid and filter won't likely correct a problem. If that filter is pluged, you have a serious problem! Installing a shift improver kei will only correct the problem if there is a stuck valve or some other problem in the valvebody that is corrected with it's installation.
 

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Had a TH400 that acted sort of like that once and it turned out to be a broken spring on the governor. Tranny wouldn't shift above 1st. Pretty easy to check - it slips right out after taking off the big cover on the tail shaft opposite the speedo gear drive.

Yours does sound more like a vacuum modulation problem though.
 

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Discussion Starter #6
Vacuum Problem

Suppose it actually was a vacuum problem. If I had no vacuum, or very little vacuum going to the modulator, the transmission should still shift up, just really late right? If it does shift up really late, how late is that? 3000 rpm, or 7000 rpm?

Also, could I have a little more detail on the governor. I am going to install that kit tomorrow, and I will take a look at that governor at the same time.

Also, thank you everyone for the help. I will make sure to post what worked to solve the problem, for future reference.
 

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If the tranny will not move till you shift to manual low gear .... the roller clutch is not holding. It is broken , installed back wards or something

When you shift to manual low... the low / reverse friction pack is applied. The vehicle will then move from a stop.

The govenor , vacuum modulator has NOTHING to do with this problem of no forward movement in "D" when the vehicle is stopped

Not shifting after the vehicle is moving... that is a different problem.

After the vehicle is moving then......... the govenor and vacuum modulator come into the operation of the tranny.
 
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The reason that I mentioned the governor is that it sounds like the trans is not downshifting, since you said that it goes right if you manually downshift. The governor is supposed to cause the downshift, and will usually cause no downshift if there is a problem with it.

The governor is located behind a large round cover at the rear area or the case. The cover, many times has a heavy wire clip over it. After prying off the cover the governor pulls right out. It should have a nylon or plastic gear on one end and 2 weights on the other. Check the gear for broken or missing teethThe center part has slots and a valve inside it. Looking in the slots, you can see the valve. Holding the governor vertically by the gear, and squeezing the weights together and releasing them, should move the valve freely. Usually, if the valve is sticking, it can be cleaned with brake clean or a similar product and shaking, the lubricate with trans fluid. If the valve cannot be freed up that way it must be removed and cleaned. The valve is removed by removing the roll pin that holds in the gear, remove the gear, and the valve comes right out.

Good Luck
 

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Crosley said:
If the tranny will not move till you shift to manual low gear .... the roller clutch is not holding. It is broken , installed back wards or something

When you shift to manual low... the low / reverse friction pack is applied. The vehicle will then move from a stop.

The govenor , vacuum modulator has NOTHING to do with this problem of no forward movement in "D" when the vehicle is stopped

Not shifting after the vehicle is moving... that is a different problem.

After the vehicle is moving then......... the govenor and vacuum modulator come into the operation of the tranny.
I'm going to have to agree with Crosley. Several times I've seen a broken govenor and the car will move in drive, it will just be stuck in first gear.
 

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Discussion Starter #10
Status so far

Ok, today I drained the fluid in the car, and replaced it with new quality transmission fluid. I used a vacuum guage on the intake manifold - 14 to 15 " of Hg. No signs of any vacuum leaks. I checked the kick down cable - it is just fine. The car still works great in drive and reverse, but no 2nd or 3rd gear.

So, it must be the governor, as suggestic in this thread. Also, is the governor related to the speedo drive gear?? My speedometer has stopped working. I know there is a plastic gear on the rear driveshaft in the tranny. Would a broken governor and non-functioning speedo sender be related??
 

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the govenor and speed-O gears are different and separtate on the T-350 tranny.

No up shifts does point to a bad plastic gear on the govenor as adtkart points out.

If the govenor does NOT spin, the tranny does not know it is moving and oil pressure from the govenor is not raised to move shift valves
 

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Discussion Starter #12
Ok, so I swapped it out, and this is what I noticed

Ok, so I swapped the tranny out. To be technically correct, it is a TH350CH. If that has any significance, I don't know. Well, I noticed two things possibly wrong when I removed it. First, the TV cable looked like it could have been stuck in the up possition at the point where it bolts to the tranny case. But, the tranny should still drive while in Drive, it will just stay in 1st gear (I am assuming). Second, and more significantly, I found a hairline crack and a slight kink in the tranny cooler lines. The hairline crack did not leak fluid, so it must have been pulling air into the line with the fluid. That can't be good for it (right?). The kink also should not be good for it, putting strain on the pump (right?). Other than that it seemed fine. No metal particles, no burned fluid, nothing. The plastic gear inside the tailshaft housing (not the speedo gear, but the one further to the front) was fine. I believe this goes to the governor. Also, I stated that my speedometer was not working. The cause for this was the plastic gear on the tailshaft inside the housing had moved forward towards the front of the tranny. The metal clip that is supposed to retain the plastic gear did not have the little tip that sticks into the tail shaft. So, the speedo works on my car again.
Also, something that I learned. Don't buy the TH350 shift improver kit if you have a TH350CH. The instructions say the TH350 kit won't work. Damn. Ok, again thank all of you for your help. -Ed
 
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