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Discussion Starter #1
Hello, I just got a check engine light with the code p0734 and i have no idea what to do. the dealership want over $200 just to check the problem for me. the code is "P0734 gear 4 incorrect ratio." I cannot find any information on any 4th gens about this topic and i have no clue what to do.
Thank you :(
 

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P0734 means the trans slipped internally while in 4th gear.

Are you having any problems with it now? Does it drive OK, and shift through all the gears 1-2-3-4-5 OK?

The typical reason for P0734 is a bad OD clutch (either the clutch discs are burned, or one of the piston seals is cut or damaged, resulting in a leak, resulting in reduced capacity). But if the OD clutch is bad, you should continue to experience slippage. And the OD clutch has to carry more torque in 5th gear than in 4th, so usually you get a P0735 (Gear Ratio Error in 5th) fault before you start blowing P0734s.

If you keep getting P0734 and/or P0735 faults, and notice trans slippage or weird behavior (shifts back and forth 4-5-4-5-4-5), then you likely have a compromised OD clutch pack, which calls for removing the trans and tearing it partway down to inspect / replace the OD clutch pack. But if everything seems OK now (and especially if you can tip into it in 5th gear without blowing any faults), then maybe you set the P0734 due to a one-time glitch, like a wacky speed sensor reading or a sudden dip in line pressure (due to low oil level or a bad filter).

The PCM saves a block of data (called DTC Event Data) each time a trans fault is set, which shows what was happening at the moment the fault occurred. A dealer can read this data using a scan tool. Your PCM should have six (6) blocks of DTC Event Data, so it will save data for up to 6 occurrences. The dealer should review this data before touching the trans at all. The data will show whether the P0734 was caused by a speed sensor glitch or a dip in line pressure, so you can rule those possibilities in or out. They should read (and print out) the DTC Event Data for you for a minimal charge (like maybe 15 minutes of labor), so you should be able to get that done for much less than $200.
 

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Discussion Starter #3
I will ask the dealer if they can print that out for me but knowing them, they will most likely decline. however, I could shift into 4th from 3rd many times and it would shift normally, but sometimes when im crusing it would have a really really hard shift. I have given it full throttle and hit 4th and it shifts fine a lot of the times, but I cleared the code the first time and drove it again for a few days and the code came back after a few days and many bad shifts :/ but also many good ones. Using one of my code readers, during the time with no check engine light, I plugged it in and said it is monitoring p0735 but when the check engine light returned it was only the p0734 code.
 

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Sounds like a weak OD clutch, then.

Also, my apologies... I was incorrect on the torque levels for 4th vs 5th gear. I was thinking of the diesel (68RFE) trans. If you have a 1500 truck, 4th and 5th are both overdrive gears, so the torque on OD is similar in both. OD is also used in 3rd (direct) gear, but it carries less torque there than in 4th or 5th.

I would drive gently when in 4th or 5th gear, to avoid toasting your OD clutch any further. You will eventually need to pull the trans and inspect / repair OD, but in the meantime go easy, and if you need to stomp on it, tap it down manually to 3rd gear first. That will help to protect your OD clutch.
 

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Discussion Starter #5
I have the 6 speed, so does the overdrive clutch work for the 4th 5th 6th gears?
the dealership told me they would want about $1,200 just to open the transmission and close it again, no parts or anything.
How hard would it be for someone to change it at home with a few friends? I don't mind working long hours on it, but is it way to hard? or is it just easy but a long process?
thanks for all your help so far
 

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I have the 6 speed, so does the overdrive clutch work for the 4th 5th 6th gears?
the dealership told me they would want about $1,200 just to open the transmission and close it again, no parts or anything.
How hard would it be for someone to change it at home with a few friends? I don't mind working long hours on it, but is it way to hard? or is it just easy but a long process?
thanks for all your help so far
Do you have a 1500 truck, or a 2500? In a 1500 truck, you would have the 65RFE transmission, which does have six speeds, but only uses five of them in normal driving (I'm referring to those as 1st thru 5th gears). The extra gear is in between 2nd and 3rd.

It takes about 10-12 hours of labor to pull the trans, tear it down, put it back together, and reinstall it, so that's why they're quoting you $1200. You would just add onto that any parts that need to be replaced (shouldn't add any more labor).

Rebuilding the trans yourself isn't really difficult, but it is a long process and you do need to be careful. Do you have a hand press you can use (to compress some of the clutch springs in order to get snap rings in and out)? Other than that, it's mostly all normal hand tools.

If you decide to go with the DIY method, PM me your email address and I can send you some hints and tips.
 

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Discussion Starter #7
So when I drive the truck in manual mode? Can I let it shift from 3-4? or should i try to keep it 3 and under? (sounds kinda confusing)

I was thinking of taking out the transmission then taking it to the dealership, letting them open the transmission and work on it, then I would just have to reinstall it? or would I need to many tools and not worth the trouble?

thank you for all the fast replies
 

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So when I drive the truck in manual mode? Can I let it shift from 3-4? or should i try to keep it 3 and under? (sounds kinda confusing)

I was thinking of taking out the transmission then taking it to the dealership, letting them open the transmission and work on it, then I would just have to reinstall it? or would I need to many tools and not worth the trouble?

thank you for all the fast replies
Yes, it is confusing!! Sorry, I should have explained better: In manual shift mode (ERS), the gears are numbered 1-6 (which includes the extra gear). So the added gear is "3" in ERS mode, direct gear (normally 3rd) is "4", and the overdrive gears display as "5" and "6". So keep it in "4" and you will limit the torque on the OD clutch.

Pulling the trans yourself is a valid option, and should save you about half on the labor costs. No special tools needed to remove and install the trans, other than a trans jack, and tool for disconnecting the cooler lines (or you can carefully use a pick to pull the clip out).
 

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8 speed

off the subject but i have a 2014 with the 6 speed and have a chance to get a 8 speed from a locl yard would there be alot involved in the swap
 

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off the subject but i have a 2014 with the 6 speed and have a chance to get a 8 speed from a locl yard would there be alot involved in the swap
The short answer is: YES!

It's not just as simple as changing the trans out. You will run into lots of other issues, including (but not limited to) wrong wiring harnesses, PCM incompatibility, trans cooler system is completely different, transfer case and driveshaft(s) probably won't match (wrong length and/or connection to trans), rear trans mount different, and possibly need different rear crossmember to boot, exhaust system may be incompatible (may not clear 8-spd trans), need to add electronic shifter (and no wiring harness for that, either), etc., etc.

You will find it a lot easier (and cheaper) to simply trade for an 8-speed truck!
 

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Discussion Starter #12
So far ive just had my truck parked thinking about my possible options, but i have a few questions that i cannot find the answers online. When does the overdrive clutch engage? only on drive? or also in manual mode? because i have not felt a hard shift in manual mode yet. Also, what would the point of having a different clutch for the overdrive gears?
thanks in advance!
 

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I would suggest you have the dealer or transmission shop do the work and get a warranty on it. PITA to do the work and find out something was missed. Pulling the trans out and having the dealer do the work is opening the door to issues who's responsible if there is a problem.

Work some extra hours to pay for it.
 

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So far ive just had my truck parked thinking about my possible options, but i have a few questions that i cannot find the answers online. When does the overdrive clutch engage? only on drive? or also in manual mode? because i have not felt a hard shift in manual mode yet. Also, what would the point of having a different clutch for the overdrive gears?
thanks in advance!
The "input clutches" transmit the input torque (from the torque converter / input shaft) to one of the members in the geartrain (like the rear sun gear, or the center carrier). The input clutches are UD, OD, and Reverse. The UD clutch is applied (and carries all the input torque) in the underdrive gears (1st, 2nd, and the extra "2nd prime" gear). The OD clutch is applied (and carries all the input torque) in the overdrive gears (4th and 5th). In 3rd gear (direct gear), BOTH the UD and OD clutches are applied, and they share the torque (OD carries 67% of the input torque, UD carries 33%). Direct gear is displayed as "4" when in ERS (manual shift) mode.

So the OD clutch is on in 3rd gear, but since it only has to carry 2/3 of the input torque, it will not slip if it still has most of its capacity. So you can often limit the trans to 3rd (direct) gear ("4" in manual mode) and still drive it OK, even if the OD clutch is weak (and slips in the overdrive gears).
 

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Discussion Starter #15
you're really helpful, im learning so much! but what would the point of having 2 different clutches for the different gears? Also, when I engage Ers and shift into any gear it has always shifted fine. even under WOT, the only time i feel the bad shifts is when in drive. But would previously having a tune on the car cause a burnt OD clutch or would it be excessive speeding?
 

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you're really helpful, im learning so much! but what would the point of having 2 different clutches for the different gears? Also, when I engage Ers and shift into any gear it has always shifted fine. even under WOT, the only time i feel the bad shifts is when in drive. But would previously having a tune on the car cause a burnt OD clutch or would it be excessive speeding?
You HAVE to have 2 different clutches in order to have 2 different gear ratios. Generally, in a typical transmission (automatic or manual), all the gears are constantly in mesh with each other. For manual transmissions, coned dog clutches are used to connect the proper gear to the output / intermediate shaft (you select a different gear for each gear ratio). For automatics, multi-disc friction clutches are used to send the input torque to the proper gear/element, and to connect reaction torque (from some other gear/element) to the case. So typically there are two different clutches applied (one for the input torque, one for the reaction torque) in any particular gear (for an automatic). Many automatics now also use clutches to engage or disengage connections between various geartrain members, so in some cases there are three different clutches applied for a particular gear ratio.

Same clutches are used in ERS mode versus Drive. If you are seeing a difference, it may be that you are delaying the shift into the upper gears (when using ERS) until you have backed off the torque level.

Excessive speeding should not cause clutch distress. Clutches get burned due to high energy during shifts, or by slippage when engaged. So it's not high speed that's the typical problem; it's excessive back-and-forth shifting, or excessive torque levels (like due to a tune).
 

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Excessive speeding should not cause clutch distress. Clutches get burned due to high energy during shifts, or by slippage when engaged. So it's not high speed that's the typical problem; it's excessive back-and-forth shifting, or excessive torque levels (like due to a tune).
Or, in my experiences, towing or hauling higher payloads without using "Tow/Haul" mode
 

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The short answer is: YES!

It's not just as simple as changing the trans out. You will run into lots of other issues, including (but not limited to) wrong wiring harnesses, PCM incompatibility, trans cooler system is completely different, transfer case and driveshaft(s) probably won't match (wrong length and/or connection to trans), rear trans mount different, and possibly need different rear crossmember to boot, exhaust system may be incompatible (may not clear 8-spd trans), need to add electronic shifter (and no wiring harness for that, either), etc., etc.

You will find it a lot easier (and cheaper) to simply trade for an 8-speed truck!
Wow my dreams of swapping in the 8 speed just went out the window. Just so I understand; driving in D you have 1-5 gears and driving in manual you have 1-6 gears? Engaging the manual driving function activates the extra gear?
 

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... Just so I understand; driving in D you have 1-5 gears and driving in manual you have 1-6 gears? Engaging the manual driving function activates the extra gear?
Yes, that is correct.

Normal driving you get 1-2-3-4-5.

In ERS mode you get 1-2-2P-3-4-5 but they are displayed as 1-2-3-4-5-6. So "3" in ERS mode is 2nd prime gear (the added gear). "4" is direct gear (which is normally 3rd).
 

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Great Thread

Most informative thread I have read in a while. Thanks for sharing your knowledge. One more question. To engage 2p do I have to go thru all gears manually or simply put it in 6
 
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