Intermitent Reverse Problem

[IdleUp]

I just noticed but it looks like this line is right up against the exhaust pipe _ I wounder if it's burnt and leaking air?

I'm still waiting to pick up my truck, but I noticed that every time I cold start the engine, I can get it into reverse a few times then it won't go in at all. Maybe its something to do with the low air pressure or just being cold ??

Thanks

[Rob]

I'm still waiting to pick up my truck, but I noticed that every time I cold start the engine, I can get it into reverse a few times then it won't go in at all. Maybe its something to do with the low air pressure or just being cold ??

Thanks

Typical of the problems you mention.

Rob

[IdleUp]

Typical of the problems you mention.

Rob

Rob,

What's your thoughts why it would only shift when cold and or with low pressure?

Thanks

[IdleUp]

By the way, I was right that line up against the exhaust is burnt half in two, but it's not leaking air and it runs aft (somewhere).

Edited January 14, 2009 by IdleUp

[Rob]

Rob,

What's your thoughts why it would only shift when cold and or with low pressure?

Thanks

Digging deep into the cold storage locker of unintelligible intelligence:

When the truck has set for a spell without air pressure, the internal "O" ring expands slightly making a seal against the bore. When air pressure is applied, the "O" ring is slightly compressed, and the escaping air from an ineffective seal lets the "O" rings take a set that does not seal until they are allowed to expand again. Those air cylinders have pressure applied on both sides of the piston during normal usage except when the funtion it performs is selected, then only one side of the piston is pressurized. Once the ring is compressed, it will remain that way until pressure is removed and the process starts again.

If you were to get the area very warm they would work fine; They probably would work acceptable in the summer as they are due to expansion of the piston, bore, and rings.

Just my opinion though.

Rob

[IdleUp]

Thanks Rob - it all makes sense now!

Bundle Up!

[Rob]

Thanks Rob - it all makes sense now!

Bundle Up!

-16 DEGREES FARHEIENT HERE!

Need to wear two pairs of underware to keep the boys warm this morning!!

Rob

[IdleUp]

Rob,

Let me ask you a question - I finally got to pick up my truck today and would you believe it wouldn't start so it's still sitting down there. It fired right up every other time i went down there.

I guess the 16 degree weather might be the fault. I have 3 good batteries, I even jumped the battery with my truck and it still turned over so slow it wouldn't start. Is this normal for these Macks?

Does the engine have pre-heat?

Where should I shoot the ether?

Thanks

[Rob]

Rob,

Let me ask you a question - I finally got to pick up my truck today and would you believe it wouldn't start so it's still sitting down there. It fired right up every other time i went down there.

I guess the 16 degree weather might be the fault. I have 3 good batteries, I even jumped the battery with my truck and it still turned over so slow it wouldn't start. Is this normal for these Macks?

Does the engine have pre-heat?

Where should I shoot the ether?

Thanks

I don't remember the engine that is in it but I seem to remember an E6-350. If the truck does not have a multi-grade oil installed such as 15W-40, but rather a straight weight such as SAE 30, it will be damned hard to crank over at low temps unless it is equipt with an immersion heater that works.

I would wrap a blanket, or tarp around the lower part of the truck and turn on a torpedo heater, (salamander) pointed under the truck for about 15 minutes. It will crank right over when the oil is thinned down a little bit from the heat.

I would plan to change the oil and service the truck right after you got it to it's new place of residence.

I'm not a big fan of ether, but a small shot in the air cleaner, or pipe to the turbo is where it goes. Best if someone is cranking the engine while another shoots the ether sparingly.

There are no preheaters, or glow plugs to be concerned with. The engine is direct injected and does not use them.

Rob

[IdleUp]

I don't remember the engine that is in it but I seem to remember an E6-350. If the truck does not have a multi-grade oil installed such as 15W-40, but rather a straight weight such as SAE 30, it will be damned hard to crank over at low temps unless it is equipt with an immersion heater that works.

I would wrap a blanket, or tarp around the lower part of the truck and turn on a torpedo heater, (salamander) pointed under the truck for about 15 minutes. It will crank right over when the oil is thinned down a little bit from the heat.

I would plan to change the oil and service the truck right after you got it to it's new place of residence.

I'm not a big fan of ether, but a small shot in the air cleaner, or pipe to the turbo is where it goes. Best if someone is cranking the engine while another shoots the ether sparingly.

There are no preheaters, or glow plugs to be concerned with. The engine is direct injected and does not use them.

Rob

Rob,

I finally got the rag started and drove it home I removed th batteries and charged them up - I snapped a few images of the reverse module just to confirm this is the right unit. I assume I just remove the four bolts right?

I also posted a thread on the interior forum looking for some interior parts.

Edited January 19, 2009 by IdleUp

[fjh]

That is compound low!

reverse is on the rear shift cyl that looks the same size as that one back shift lid.There is a switch on the dash for that one.

[Rob]

FJH is correct, that is the compound low reduction cylinder. You will want to rebuild it also while you have the floor section out of the cab as it is very easy to get to.

The reverse shift cylinder is the one at the rear on the rt. side of the transmission. The cylinder that has the external bolts running the outside of the cylinder is the high/low range cylinder. It is about centerline of the transmission.

Rob

[IdleUp]

Ok I'll snap an image of the rear module today so I know what I'm dealing with.

Thanks!!

[IdleUp]

Ok - I just shot these images of the rear shifter module from both sides - looks like it might be the one from the right side of the truck, ( upper image) I would imagine the wire goes to the backup beeper and dash light.

Do I just remove the 4 bolts on the end of the unit to access the shifter O rings?

Edited January 19, 2009 by IdleUp

[fjh]

Ok - I just shot these images of the rear shifter module from both sides - looks like it might be the one from the right side of the truck, ( upper image) I would imagine the wire goes to the backup beeper and dash light.

Do I just remove the 4 bolts on the end of the unit to access the shifter O rings?

No you have to remove the whole module! (Shiftlid) its a breeze on tht model of truck You can have it out of there in less than an hour!If your hving an intemitant revers problem still it maybe the larger cyl causing the problem there is a lock out pin in the lid,If the spliter does not make center for any reason the reverse air shift will be locked out!

When you get the lid off check to see that the set bolts are tight on the shift yokes in the lid that is the first check of the day!

If one or both are loose remove and apply locktight and re assemble. If not remove the cover of the big piston and check for any rust or broken snap ring.

[Rob]

No you have to remove the whole module! (Shiftlid) its a breeze on tht model of truck You can have it out of there in less than an hour!If your hving an intemitant revers problem still it maybe the larger cyl causing the problem there is a lock out pin in the lid,If the spliter does not make center for any reason the reverse air shift will be locked out!

When you get the lid off check to see that the set bolts are tight on the shift yokes that is the first check of the day!

As FJH suggests: Remove the complete shift cover assembly. When the cover is on a bench and inverted, there will be two shift forks; One fork is flat with rounded ends, (reverse/forward), the other is a round ball, (gear selection). Remove the capscrews from the endplate of the reverse shift cylinder and remove the endplate. Remove the set bolt from the reverse shifting fork so it slides easily on it's shift rail within the cover. Center the ball ended shift fork within it's travel, and pull the reverse shifting piston from it's bore towards the rear of the housing by using your fingers to force the shift rail to the rear. As FJH states there is a centering, or lockout pin the precludes the engagement of reverse if the main transmission fork is not is the neutral position, (centered).

I have a photo of the shift cover and will send it to you. There is also a proceedure how to properly adjust, and center the forks upon reinstallation. You will need to have a supply of air, fittings, and a regulator set to 60psi to do this alignment, (from memory). It will also have much less room for error if the universal joint at the back of the transmission is disconnected to ensure the tranmission is in neutral. If you have either a loose locknut, or take it loose to re ring the piston on the high/low cylinder, you must readjust for neutral or you will never be able to select reverse.

I've only had this one Mack air shifted transmission so I am no expert by any means. My experience is derived through trial and error, then analysis. But it does seem to work for me.

I would think that an E7-400 would be adequate for power citing that it is a mechanical engine. Never have seen an E7 series myself, (too new).

Rob

[theakerstwo]

Rob the exspresniance that you got on that trans is the best that you cant get. If it ant right redo it, if it breaks you pay for it and in the end you remenber it. I have been a seft taught.

[Rob]

Rob the exspresniance that you got on that trans is the best that you cant get. If it ant right redo it, if it breaks you pay for it and in the end you remenber it. I have been a seft taught.

Yes Glenn. I have learned more on the kitchen table than I ever could in school as I found formal education too "structured", and could not hold my interest. Grandma never did like me tearing into a Rochester, Holley, or Carter carburator on the kitchen table, but grandpa always would overide her, (finally got my own bench in the basement). I guess Briggs & Stratton, Tecumseh, and Clinton engines were the final straw. When I discovered how to repair and paint wrecked cars, I got the garage!

Rob

[fjh]

As FJH suggests: Remove the complete shift cover assembly. When the cover is on a bench and inverted, there will be two shift forks; One fork is flat with rounded ends, (reverse/forward), the other is a round ball, (gear selection). Remove the capscrews from the endplate of the reverse shift cylinder and remove the endplate. Remove the set bolt from the reverse shifting fork so it slides easily on it's shift rail within the cover. Center the ball ended shift fork within it's travel, and pull the reverse shifting piston from it's bore towards the rear of the housing by using your fingers to force the shift rail to the rear. As FJH states there is a centering, or lockout pin the precludes the engagement of reverse if the main transmission fork is not is the neutral position, (centered).

I have a photo of the shift cover and will send it to you. There is also a proceedure how to properly adjust, and center the forks upon reinstallation. You will need to have a supply of air, fittings, and a regulator set to 60psi to do this alignment, (from memory). It will also have much less room for error if the universal joint at the back of the transmission is disconnected to ensure the tranmission is in neutral. If you have either a loose locknut, or take it loose to re ring the piston on the high/low cylinder, you must readjust for neutral or you will never be able to select reverse.

I've only had this one Mack air shifted transmission so I am no expert by any means. My experience is derived through trial and error, then analysis. But it does seem to work for me.

I would think that an E7-400 would be adequate for power citing that it is a mechanical engine. Never have seen an E7 series myself, (too new).

Rob

The adjusting nut that you are refering to was deleted in later years this likly being one of them!If the split doesent center its self you have to shim the spring!When you get to the part in the rebiuld routine where you apply equal air preasure to both sides of the split hopfully you will have no problems.

Most times its OK.Also in the tips Rob gave to ya if the shift fork bolts were not tight when you go to loosen them THAT can be a 90% posability of your problem!

[Rob]

The adjusting nut that you are refering to was deleted in later years this likly being one of them!If the split doesent center its self you have to shim the spring!When you get to the part in the rebiuld routine where you apply equal air preasure to both sides of the split hopfully you will have no problems.

Most times its OK.Also in the tips Rob gave to ya if the shift fork bolts were not tight when you go to loosen them THAT can be a 90% posability of your problem!

I don't know how late my service manuals represent. The newest engine is called an ENDT1000 and not an E9 series. The highest horse rating is also 400 for that engine.

They do cover my 73, and my 1978 Macks quite nicely, and I seem to recall the last reprint date as 3/79.

Very sorry if my information has been misleading or confusing with your issue. There are obviously "updates" that I am unaware of.

Rob

[IdleUp]

Thanks so much for all the info - I'm going down tomorrow to pick up the rebuilding kit. Rob did you find that image of the shifter plate, I'm curious what it looks like.

I finally figured out why it goes into reverse. If the air pressure is below 60 lbs then I can generally get it in reverse as many times as I like, however as soon as the buzzer goes back off, it won't go in reverse any longer. I thought someone told me it might be a quick release valve. I'm wondering if that's the problem.

Thanks

By the way, my email is: mail@rotory.com

Edited January 20, 2009 by IdleUp

[fjh]

Thanks so much for all the info - I'm going down tomorrow to pick up the rebuilding kit. Rob did you find that image of the shifter plate, I'm curious what it looks like.

I finally figured out why it goes into reverse. If the air pressure is below 60 lbs then I can generally get it in reverse as many times as I like, however as soon as the buzzer goes back off, it won't go in reverse any longer. I thought someone told me it might be a quick release valve. I'm wondering if that's the problem.

Thanks

By the way, my email is: mail@rotory.com

Bro ,ID be checking the plumbing as well!

When reverse is selected you should have air at the forward port of the reverse cyl No air to the rear port of that cyl (if you remove that rear line there should be no air coming from or going to it! if itscoming from it its leaking inside and needs orings!)Also when reverse is selected you will have air to both sides of the spliter cyl holding the split in neutral.

[IdleUp]

Bro ,ID be checking the plumbing as well!

When reverse is selected you should have air at the forward port of the reverse cyl No air to the rear port of that cyl (if you remove that rear line there should be no air coming from or going to it! if itscoming from it its leaking inside and needs orings!)Also when reverse is selected you will have air to both sides of the spliter cyl holding the split in neutral.

I picked up the O-ring kit and a cover gasket today - I included a part layout below the guy gave me. I'm going to check the airlines as suggested. Is the reverse piston the one on the right #4?

The guy at the dealer said it could be the shifter control!!!

Thanks

[fjh]

I picked up the O-ring kit and a cover gasket today - I included a part layout below the guy gave me. I'm going to check the airlines as suggested. Is the reverse piston the one on the right #4?

The guy at the dealer said it could be the shifter control!!!

Thanks

Number 20 is the revese piston.

Read carfully what I wrote last ! Remove the rear line on the rev cyl with the air shift selector in rev ,check to besure there is no air escaping the cyl thru the fitting or coming down that line.if there is air on the line it may be the shift knob.

[Rob]

Number 20 is the revese piston.

Read carfully what I wrote last ! Remove the rear line on the rev cyl with the air shift selector in rev ,check to besure there is no air escaping the cyl thru the fitting or coming down that line.if there is air on the line it may be the shift knob.

save yourself the headache and rebuild the "Selectair" valve also. Completely rebuild that shift cover with all new rings, (teflon rings also).

That shift cover is cast iron and heavy. It also has locating dowels in the cover into the top of the transmission case and can bit a bit tricky to get to pop loose.

Rob