transmission won't shift to 3rd gear

[wreckless17]

I have 78 chieftain and transmission seems like it shifts good until you get to freeway speeds at 55 mph the rpms just get higher and higher the faster you go.  also if I shift manually it seems like its shifts three times but the rpms still are way too high the faster you go

[Old Man Powell]

I'm no expert, but I'll try helping. Are you knew to this rig or have you had it for a while? I ask only beacuse with the 3 speed tranny these things run practically 3k RPM at highway speeds. On my first "classic" RV I had to adjust mentally to hearing the engine run at those higher RPM's.

Now, if it's truly not going into third you might want to check vacuum line from carb. If you have a vacuum gage make sure it isn't bottoming out when the tranny is trying to go into third. Of course, check your fluid level, color and odor.

That's about the extent of my knowledge so someone else please jump in with more suggestions.

One thing I will recommend... if all else fails, go buy some Lucas Stop Slip transmission additive. I ususally don't put much faith into all these "solutions in a bottle," but I have personally seen that stuff same two transmission that were slipping or not shifting. I used it as a last ditch effort on an old truck I had. The tranny was shot... a used one from a junkyard was going to cost more than the truck was worth. I poured that stuff in and after a few minutes of it mixing in the transmission not only shifted again, it shifted better than it ever had. And it lasted!

My dad used it in his Dakota after his tranny started acting up. Sure enough, after it had a chance to mix in his transmission was like new. So, just something to keep in mind.

[ramit]

if it shifting 3 times that it these old rigs just roar at hwy speeds ..just turn up the radio lol W% run at 55 mph enjoy the trip

[Old Man Powell]

Good point... a loud radio will solve a lot of problems!

[legomybago]

Make sure your clutch fan isn't stuck on...that will make your engine sound like it's screaming down the highway...
Or you may have 456's and a locker in the back? lol

[wreckless17]

somethings not right because it feels like it should shift again and I can here the rpms rising the more gas I give it struggles to get up to about 65 the second I release the gAS the speed rapidly decrease back down to about second gear speeds.

the tranny doesn't slip at all it shifts smoothly it downshifts to climb perfectly this is what I don't get is at hiway speeds.

[legomybago]

How does it react driving it around on backroads? You should definetly feel the 3 speeds cruising around town. Your shift linkage from your carburator to the tranny controls your shift points. The "longer" the rod, the longer between shifts...How long has it been since tranny filter and oil change?

[DonD]

My 3 speed only shifts twice when underway. 1st to 2nd, then 2nd to 3rd.    W%

[wreckless17]

that's what im gonna do is change fluid and filter well see what happens

[cosmic]

I once thought mine wasn't shifting into 3rd,  so go in L1 Then L2 then into drive. It was like lagomybago said. my clutch fan. really made it sound like it wasn't in 3rd. What I did to be certain was pulled the 4 bolts and took the fan out. went for a quick drive and it was business as usual. So a new clutch fan it was.

[Froggy1936]

When my clutch fan locked up wile driveing in Florida I immeadiatly thought i lost the transmission . After a few feet of driving i noticed the tach was at normal position for speed . When i got to a spot that i could get off the road Investigation showed the fan was locked solid I stopped at a Advance auto store got a new clutch assy Checked into a motel parked in the back out of the way (with permission) Next day changed it right there . It is amazing how much noise the fan makes when revolving at full speed ! Make sure you check that before anything else  Frank

[ramit]

ya the stuck fan makes sinse that would make it sound like a train comin through Hm?

[Thundercloud]

Check for any disconnected or broken vacumm lines coming off the transmission. Just an idea. I had a K-5 Blazer that did that. Not sure what tranny you have and I'm no expert. That and some of that Lucas stuff is pretty good.

[TripleJ]

First establish that the trans does indeed shift into third gear then go from there.   I doubt a fluid and filter change will have any effect on this issue either way.  It won't fix a broken trans any more than it will fix a bad fan clutch

[DaveVA78Chieftain]

I do not take my engine above 45MPH in 2nd gear because engine RPM is as high or higher than 3rd gear at 55-60.  I run at 3000 RPM at 60MPH.

Dave

[Froggy1936]

There is the possibility of a stuck governor Not allowing 3rd gear A fluid change and a good additive shoud fix it If not its accessable with a tailshaft housing removal  Frank

[wreckless17]

it was the throttle shift cable I think its called that the one that goes from carb to trani I just am not sure how to properly adjust it

[UK-Winnie]

I saw this thread but I didn't didn't think of that - I had the same thing on my '63 Chrysler 300 (with a 413) when the linkage to the transmission would sometimes flip off it's bearing and it would stay in lower gears too long.

The Chrysler transmissions don't have a vacuum modulator - it's all done off the carburettor linkage.

Also I didn't realise you had a cable linkage.

If this is the problem then if you remove the cable from the trans you will see that the cable was pulling too much and preventing the little lever on the trans. from going properly to rest - you need to adjust the cable so that when the accelerator is not pressed the lever returns close to its rest position.  After that you can play with it a bit to get the shift points you prefer.

[Froggy1936]

17 First make sure the cable is operating freely (dissconect both ends and operate wile running motor oil down the cable) Its good to get the outer housing soaked with oil, With the choke held open (so throttle is fully closed ) connect cable at carb end THen wile holding Accellerator to the floor (engine off) move lever on trans forward till you fell it depress the valve against spring pressure fully adjust cable to hook up at this point . Then road test  at medium throttle trans should shift to second at approx 20 MPH then to third at approx 35 MPH  after accelerating to 40 mph press accellerator to the floor trans should downshift back to second gear and hold it till 45-50 MPH  Make sure engine and trans fluid levels are correct before road test   If trans will not upshift cable is too short or still sticking Frank