mattoliver80
Member
Caterpillar 735 articulated truck will not shift out of first gear on flat or uphill grade but will downhill. It's really got me puzzled! Any suggestions would greatly be appreciated.Reverse works normal.
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cat 735 won't shift out of first gear
- Thread starter mattoliver80
- Start date
mattoliver80
Member
Hold gear is not on or is in 8th.. About 2150 max on rpm
Nige
Senior Member
S/N prefix of the truck please ........... B1N perchance..?
Is there any significant difference to the maximum engine RPM you see when travelling on level/uphill (when the truck refuses to upshift) compared to downhill (when it will)..? If the engine is getting to higher RPM downhill than it is level/uphill then it would appear there could be a problem with lack of power. If there is no difference, read on.
My first thought if there's no difference in engine RPM uphill or downhill would be that for some reason the Lockup clutch in the converter is either not engaging at all or only partially engaging. On a downhill run even the lack up a lockup clutch would in all probability probably not prevent the truck ground speed (assisted of course by gravity) getting to a point at which a transmission upshift would be triggered. Hence the transmission upshifts.
Is there any significant difference to the maximum engine RPM you see when travelling on level/uphill (when the truck refuses to upshift) compared to downhill (when it will)..? If the engine is getting to higher RPM downhill than it is level/uphill then it would appear there could be a problem with lack of power. If there is no difference, read on.
My first thought if there's no difference in engine RPM uphill or downhill would be that for some reason the Lockup clutch in the converter is either not engaging at all or only partially engaging. On a downhill run even the lack up a lockup clutch would in all probability probably not prevent the truck ground speed (assisted of course by gravity) getting to a point at which a transmission upshift would be triggered. Hence the transmission upshifts.
mattoliver80
Member
I'm here at it now and it says model 735....product id # CAT0075.. circumstances up to this point were..throwed code for trans filter stop up,changed all oil and filter. It was not going into drive most of the time. Sometimes it would. Fluid had lots of metal on both magnets and fluid was black. Now it goes into gear fine just want shift out of first on level or uphill
mattoliver80
Member
4 mph and it throwed the code for the filter being stopped and the warning alarm sounded and wouldn't go off. That stopped after I changed filter and oil.
Nige
Senior Member
Lots of metal on magnets............. did you maybe take a photo of the metal..?
Black fluid - maybe something's burnt, most likely a clutch. Did fluid you drained smell burnt..?
Any idea when the oil was last changed and how many hours the truck's run since..?
Could still be the converter lockup clutch because the whole powertrain (converter & transmission) shares the same oil.
Did you get chance to check engine RPM on level/uphill versus downhill..? Any difference..?
Black fluid - maybe something's burnt, most likely a clutch. Did fluid you drained smell burnt..?
Any idea when the oil was last changed and how many hours the truck's run since..?
Could still be the converter lockup clutch because the whole powertrain (converter & transmission) shares the same oil.
Did you get chance to check engine RPM on level/uphill versus downhill..? Any difference..?
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mattoliver80
Member
Nige
Senior Member
No difference in engine RPM and I would be looking at the lockup clutch next, if nothing else than to eliminate it from the fault diagnosis.
A slow shift from 1st to 2nd downhill followed by (relatively) "normal" upshifts beyond 2nd could be another pointer towards the LUC. Remember 1st gear is the only one that has both converter drive & lockup, 2nd upwards is direct drive only. When you're driving the truck can you feel the LUC engage..? It should feel a bit like the truck has changed gear but in actual fact it hasn't. Is that the only 735 on the job site..? if there are others then try driving one of them and see how the LUC feels when it engages. On larger trucks it's quite noticeable from the seat, not sure about an Articulated.
That looks like "fuzz" from normal wear (although maybe in higher than normal quantity) rather than a major component breakup. A lot depends on how long ago the oil was last changed - at which point one would hope that the magnet was cleaned. But do you know this for sure..?
That magnet wouldn't necessarily frighten me too much if I knew a bit more of the previous history of the transmission and maybe also had photos of what the magnetic plug looked like on previous oil changes.
Something's wearing in there, that's for sure. How many hours does the truck have on it, or the transmission if it doesn't have the same hours as the truck..?
A slow shift from 1st to 2nd downhill followed by (relatively) "normal" upshifts beyond 2nd could be another pointer towards the LUC. Remember 1st gear is the only one that has both converter drive & lockup, 2nd upwards is direct drive only. When you're driving the truck can you feel the LUC engage..? It should feel a bit like the truck has changed gear but in actual fact it hasn't. Is that the only 735 on the job site..? if there are others then try driving one of them and see how the LUC feels when it engages. On larger trucks it's quite noticeable from the seat, not sure about an Articulated.
That looks like "fuzz" from normal wear (although maybe in higher than normal quantity) rather than a major component breakup. A lot depends on how long ago the oil was last changed - at which point one would hope that the magnet was cleaned. But do you know this for sure..?
That magnet wouldn't necessarily frighten me too much if I knew a bit more of the previous history of the transmission and maybe also had photos of what the magnetic plug looked like on previous oil changes.
Something's wearing in there, that's for sure. How many hours does the truck have on it, or the transmission if it doesn't have the same hours as the truck..?
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mattoliver80
Member
Whole truck has 9660hrs and we bought it at auction. Is there a way to check the lock up clutch or does the tranny have to be pulled. We bought 2 and they came from the same company and the other one was not bad at all and fluid was clearing.
Nige
Senior Member
As per my post above (eidted while you were typing probably) ........... try driving the other truck and see if you can feel the LUC engage, then try the problem truck.
LUC pressure should be able to be checked from outside. Let me have a look ...........
Edit: Need the Serial Number. Look at the last 8 digits of the 17-digit PIN number. They will be something like B1Nxxxxx where the x's are numbers from 0 thru 9.
LUC pressure should be able to be checked from outside. Let me have a look ...........
Edit: Need the Serial Number. Look at the last 8 digits of the 17-digit PIN number. They will be something like B1Nxxxxx where the x's are numbers from 0 thru 9.
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Irish in oz
Well-Known Member
I had a problem with a 740 playing up with gears and it turned out to be the (actual gear sensor) on the right hand side of the transmission another 740 we had also played up and it was the toothed wheel that the transmission sensor picks up off had come out of place giving false readings
Nige
Senior Member
This brings to mind another thought. If that amount of material was on themagnet, what's the chance of some metal particles adhering to the end of the magnetic pickup for the speed sensor..?
mattoliver80
Member
AWR00516 is the last 8#s... I know for a fact that the lock up is working on the other one b/c of what you said it would almost feels like it shifts but it doesn't. The one that's not shifting doesn't do it at all. Is there any way to check the converter from the outside???
Irish in oz
Well-Known Member
True that might be worth checking as its relitavely easy to get at at the back of the trans
Nige
Senior Member
Send me a PM with your e-mail address. I'll send you the Testing & Adjusting Procedure so at least you'll be able to check the converter pressures.
The LUC is operated by a solenoid valve on top of the transmission - one of 3 (upshift, downshift, & LUC). Maybe you have a wiring fault that is not allowing a signal to get to the solenoid valve, or maybe the solenoid valve itself is dodgy. I'll send you the electrical schematic as well so you can troubleshoot that side as well.
mattoliver80
Member
Nige
Senior Member
You have mail ............
mattoliver80
Member
Well I went directly to the lock up solenoid and valve to check the ohm's. It measured a lil high but still in range. So Itook off the whole solenoid to check ooperation of the valve and at first it was somewhat stuck in place, after it came free I checked the ohm's and it read way out..like 4.00 high. It said 8.7+/- .40..it reads 12.5 now. I figured what the heck and hooked it to 12v and nothing,hooked it to 24v and nothing. I ordered a new solenoid from Thompson cat and it will be there in the morning. Hope that fixes my problem and thank you so much for your help!