Problems going into drive from cold

[montreal]

We had a worrying problem occur before we set off yesterday.
The coach would not pull away in any gear. It was not warmed up but revving the engine had no effect on making it go forward or backwards.
I put a bit more transmission fluid in but i think it's at the right level.
Do I check it with the engine running? The dipstick is marked for hot and cold I think.
After switching off for 5 mins it finally 'clonked' into drive as normal.
It's done it again this 1st thing this morning but we have not left yet.
Fingers crossed. Only 300 miles to go!!

Del

[Skater]

Uh oh. This is never good.

Normally you check the transmission fluid with the engine running and in park, transmission warm, and on level ground. Some transmissions may be different, but most of the ones I've seen work that way (in fact our F-250 has a cold and hot mark like yours). Check your owner's manual.

Of course if it is low, you'll want to figure out why... it's going somewhere!

[HowieE]

Check the fluid again while the engine is running and in park. Had the rig been sitting for some time before you left home? If you do not see any trans fluid on the ground where you store the rig it may be inside. If it has been working since you left home it sound like the convertor seal may be leaking back to the trans and you have to pump the convertor full before it will apply power to the trans.

Top off the fluid level as noted above and record the level. Let it sit overnight and start the rig, try for a gear, and check the fluid level as soon as you start. Note the level and check again about 1 minute later. If the level has dropped notably the oil has been pumped somewhere.

[xrvr]

is it actually going into gear? I know nothing about as mh, but I had an sob that would not go into gear until the air pressure built up. I do not think ASare the same but just in case. Jim

[Protagonist]

Originally Posted by montreal

We had a worrying problem occur before we set off yesterday.
The coach would not pull away in any gear. It was not warmed up but revving the engine had no effect on making it go forward or backwards.
I put a bit more transmission fluid in but i think it's at the right level.
Do I check it with the engine running? The dipstick is marked for hot and cold I think.
After switching off for 5 mins it finally 'clonked' into drive as normal.
It's done it again this 1st thing this morning but we have not left yet.
Fingers crossed. Only 300 miles to go!!

Del

It has been a lot of years since I worked in a service station (back before they were "convenience stores"), but I seen to recall that you usually check the oil with the engine off, and the automatic transmission with the engine running. The "hot" and "cold" marks refer to the temperature of the transmission fluid, which you can feel if you wipe the dipstick with your finger. If it's cool enough not to burn you, go by the "cold" mark.

If the fluid is low, you have a leak somewhere. An automatic transmission is a hydraulic pump and hydraulic motor all in the same housing, and it's a sealed system except for the dipstick hole. If you're low on fluid, it's definitely leaking; vehicles can't burn off transmission fluid like the burn oil.

When you check the dipstick, look at the fluid, not just the level. The fluid should be red, clear, and slightly sweet-smelling— according to AAMCO. If it's dark-colored or has a burnt smell, the transmission has overheated at some point in the past and caused the fluid to break down. When this happens, the fluid forms a sort of varnish that can gum up the works.

If the fluid isn't overfilled, isn't low, and isn't scorched, the most likely cause of failure to go into gear would be slipping bands. This requires service by a trained mechanic.

As an aside, the "clonk" noise may not be coming from the transmission. It might be coming from a universal joint connected to the transmission's output shaft. That is a serious problem that should also be addressed by a trained mechanic.

Also, if the gearshift is going to the correct gear but the transmission isn't shifting, then the problem could be outside the transmission, in the shift linkage. Again, time for a trained mechanic.

There is a common theme here, the need for a trained mechanic. If I were you (and bear in mind, I'm not you) I wouldn't drive it any farther than the nearest repair center until problem is resolved.

[ScrapIrony-2]

I don't know if a malfunctioning overdrive unit might be the cause(don't even know if you have one)...I would go to a mechanic...the closest you want me to an engine is probably down the block...m

[montreal]

I think the fluid was low. I have had some issues with where he was parked.
When reversing out we are parked on mud which has got more churned up due to the weight and rain. This coupled with the fact that I was trying to pull away and turn on D!
Fluid had come out of the dip stick probably as it was overfilled or overheating?
Any way about a litre and a half has sorted the problem and it goes into gear from cold now.
Thanks

[Protagonist]

Originally Posted by montreal

I think the fluid was low.

Any way about a litre and a half has sorted the problem and it goes into gear from cold now.

Now, you need to find where you lost a liter and a half of transmission fluid. It had to go somewhere, and if you don't fix it, it will just keep leaking.

[Keyair]

Dell, yes the low fluid will cause a no drive or slow engagement.
Even a litre low will make a difference.
You need to figure out if it is leaking or if it overflowed, that is a warning too.
Not sure how familiar you are with Auto's as I know I was a noob untill I got here... Automatics in the UK, were rare when I lived there.
Transmission fluid should be bright red, and smell sweetish... if it makes ya jump back and turn up ya nose... its a bad sign!
The level should be checked at normal temps with engine running in P. "Rocking" to get out of mud etc is hard on the transmission and will cause overheating sometimes.

[montreal]

It's been a while. Looking into this now. I think I have a bad vacuum modulator. This could be sucking fluid out and burning it in the engine. Could explain things as it was low again after a long tuning up period and a blast on the road. Also heard that it causes a slight mis fire. Always thought it popped a bit. Any ideas? Going to change fluid and filter and modulator 1st. Governor checked and ok. Could a broken or slipping governor plastic gear cause non engagement of forward gears?

[Keyair]

Yes, Common problem, and cheap fix.
My 454 powered suburban had the same issue, and the PO spent lots of $ having the heads removed and rebuilt to cure the smoking ... only to find it was the Vacuum modulator.