I was on my way to a local cruise night and I lost 3rd gear. I topped off the fluid on my way home but then I lost 2nd gear. I had to drive all the way home in 1st.ou: Okay, enough of the sob story. I'm looking for a VERY affordable tranny to swap in. Maybe I'll try to tear apart the one I have for a rebuild while I drive on the replacement. Can the short and long shafts be be swapped? Thanks, MARK
I have a 69 short shaft out of a 69 vette, It belongs to the lady next door ! she would like to get $350.00 for it but might be negotiable ? Were in northern ohio Eastlake. Gary
Best bet is to rebuild the trans you have. Take it to a trans shop and find out what the problem is.....such as a worn case....if so, you can use any BOP TH400 case to fix it. You can not use a longshaft TH400 since you will need to shorten your driveshaft and that costs money since you will need to rebalance it. Also, longshaft will affect your pinion angle and create vibrations. The TH400 from the Vette will not work since it has a Chevy bellhousing bolt pattern.
You can use the long shaft tranny as long as you pull it down and swap the output shaft. But, since you have to pull it apart to do this, you may as well pull yours apart and see what's up. George is right, the Corvette transmission will not bolt up. You MAY find that you only need to hook up the vacuum hose to the tranny. You SHOULD be able to manual-shift it at say 30 MPH and it will jump into 2nd. That's the best test to determine if it's a vacuum related problem. Could also have a governor problem which is also very easy unless the case bushing has popped out in which case you will see the governor gear chewed up. If you see this, pull the tranny!
I checked the vacuum hose at the carb and it was connected. That's the first thing I thought of since I just added a 1" spacer. I thought I forgot to connect it. I also tried the manual shifting and that didn't work. When I get up to 25mph, the car bucks like it wants to shift. How will I know if the governer needs replaced?
Take a look at the trans modulator and see if the line is on it. I had something like that happen to me and that was the problem. Also could be the modulator itself.
Sounds like the lack of vacuum is not the problem since you can't manual shift it but just for laughs did you make sure that you have vacuum at the modulator? As far as the governor goes, pull it out and look at it. It is a very rare day when one of them "goes" suddenly, the only real reason, as I say, would be if the gear is chewed up and the governor won't rotate anymore, which is caused by the rear case bushing working it's way out and the governor gear becomes mis-aligned and the plastic gear wears out rapidly. ( Whew, that was a long sentence! ) This only seems to happen on TH 400s and I've seen more than several do this over the years. Failing these possible scenarios, it sounds like the front pump is going away, ( ie scarred housing and gears ) and you are losing line pressure. When I first read about your tranny problems this is what I thought of first since that is frequently the order of things happening ( first you lose 3rd, then a little later 2nd ) but it could have been other outside chances and they are easier to eliminate as possible problems before you pull the tranny out!
I Had a similar problem once on a 73 Electra. It turned out to be a carbon plugged vacuum line. Cleaned line out and everything went back to normal.
Let's see... I checked the vacuum line at the modulator and it was connected. I didn't check to see if the line was plugged but if it was I should still be able to manually shift shouldn't I? Even if the modulator is bad, I should still be able to manually shift? The only symptom I ever had was when the car would sit for a couple weeks, it had a hard time shifting in to 3rd (like not until around 3200rpm). But then it would be okay. If I drove it once or twice a week it never had a problem. Soooo, if I pull out the governor and it has a chewed up gear and I replace it, it's just going to get chewed up again?
Yes, it will chew up again in a few hundred miles. It takes finess to make it manual shift it and make it work. What I do is get it up to 30 mph in manual first gear and bump it into 2nd manually. If it doesn't go into 2nd I pull it back in 1st and do it again. Usually it will upshift the 1st time or two if it is a vacuum problem. If the sympton started out with a delayed 3rd shift when cold I would look very carefully for vacuum going to the modulator. Pull the vacuum line off "at the modulator" and make sure you have good vacuum there. I would also check the fluid and see if it smells burnt. If it is, you are probably wasting your time, if not, look carefully at the modulator and governor!
I'm going to pull out the governor when I get home this afternoon. If the gear is all chewed up then I will want to get another 400 and start rebuilding it. I can't afford to buy a "good running" 400 right now. I rebuilt a 200r4 2 years ago without any problems and I understand the 400 is easier. I never did detect any burnt fluid.
All righty now. I pulled the governor and it looked next to perfect. I checked the vacuum at the modulator and got 2 inch lbs. Ah ha! I checked the vacuum at the carb and was getting 18 in lbs. I found the rubber hose going to the modulator was not sealing properly. I cut a new piece of hose and retested the vacuum at 18 in lbs at the mod. I hooked it up and took a drive but it still wouldn't shift auto or manually. Then I remembered I didn't put the fluid back in. I checked the stick and found it a qrt low so I topped it off and retested. ...but it still didn't shift.:idea2: The fluid was completely pink by the way. Maybe it is the pump but do they just suddenly go out like that? Here's the governor.
My experience says that if the car moves, you have enough pump pressure that it ought shift. This sounds odd. Check one more thing -- disconnect your electrical connector and see if it shifts now. If it does, you have 12 volts going to the solenoid and the tranny THINKS it needs to hold out on shifting since it thinks you are at full throttle. Governor looks fine. Is the transmission whining? They will whine if the filter is restricted and that could POSSIBLY be restricting fluid from getting to the pistons to apply them. Let me continue thinking about this tonight!
Man this stinks! When I was road testing last night, I had a GT Mustang pull up beside me. I had to give him the "no, sorry, not tonight" wave. Anyway, I haven't hear any whine yet. And when I put it in D or R it gives a solid thunk like I would expect. The funny thing is, I can't get it to shift into 2nd but when I get up to 30mph and then coast it feels likes it's in 2nd. If I pull the shifter back to L1 I feel it shift.
All of those symptons seem to point to a vacuum modulator issue. I'm not sure I have ever seen one go bad but I sure think I would pop another one in there and make sure it has good vacuum to it. Wish the car was here -- I like figuring out stuff like this.
Go for the modulator first. Yes they do go bad. Also, as some stated the line does carbon up and I have seen the lines crack. The problem you describe sure sounds vacuum/modulator connected. It is cheaper and easier to work on this for awhile than pulling tthe transmission to find nothing wrong with it. JIm N.
Last night I disconnected the electrical connector just to make sure that wasn't the problem but that didn't make a difference. I picked up a new modulator and filter. I'll replace the modulator first and if that doesn't work, I'll pull the pan and replace the filter.
Don't think the filter would cause this problem, esp. if there is no whining noise coming from the tranny.
I replaced the modulator this morning and re-checked my vacuum line. It didn't make any difference. I got the car up to 4500rpm in first gear to see if maybe it would skip 2nd but it didn't.
