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| 83 904T shudder at 35-40 MPH https://slantsix.org/forum/viewtopic.php?t=39894 |
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| Author: | Reed [ Mon Apr 19, 2010 11:56 am ] |
| Post subject: | 83 904T shudder at 35-40 MPH |
Yet again, transmission problems with my brother's 83 Dodge shorty van. 225/904T. The transmission currently in the van is one I bought out of a junkyard a few months back. It is a 1984 A-904T. Lockup, wide ratio gearset. The transmission had writing on it indicating it had been rebuilt, and the torque converter had a stocker on it saying "Remanufactured 10/06". So, all indications were that this transmission was rebuilt in late 06 or early 07. Before I installed the transmission, I drained the fluid (including the torque converter as best I could), refilled it with ATF +4, changed the filter, and installed a Transgo TF SC shift it. Initial, the transmission performed fine. Shifts were firm, but not harsh, no slipping between gears, all was good. Over time, a problem has developed. Low speed operation is fine, high speed operation is almost fine, but the transmission gets a NASTY shudder between 35-40 MPH. It is only at that speed, and not the corresponing engine RPM or throttle position, that the shudder occurs. At higher speeds the transmission does not shudder at the same throttle position or engine RPM. Additionally, there is no kickdown at highway speeds. Cruising at 50+, the transmission will not kickdown when the throttle is depressed rapidly. Low speed/part throttle kickdown seems to be working great. Adding to the mix is the fact that my brother had a transmission coler that was literally half the size of the radiator in his van. Roughly 1x2.5 feet. I am hoping that the problem is something as simple as the low/reverse band needs adjustment. However, I am going to get a set of transmission line pressure gauges and do a full diagnosis, hopefully this coming weekend. I am also thinking it might be the torque converter locking up prematurely or somehow incorrectly and lugging the motor. Anybody have any suggestions or tips as to where I should be looking to track down this shudder? How do I check the torque converter lockup to see if that is the problem? Thanks! |
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| Author: | SlantSixDan [ Mon Apr 19, 2010 12:03 pm ] |
| Post subject: | |
Have you verified the torque converter is actually locking up? Speed range you mention makes me a little suspicious because that's the lower end of the range at which you might expect the lockup to occur. (It's actually about 10mph too slow...) |
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| Author: | Reed [ Mon Apr 19, 2010 1:30 pm ] |
| Post subject: | |
Hmmmmm. No, I haven't. I'll check that this weekend. Thanks. |
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| Author: | Doc [ Mon Apr 19, 2010 1:31 pm ] |
| Post subject: | |
My 81 LFG Lock-up 904 used to lock-up with a shutter... at 40 MPH. We "lived with it" for a few years and then I found a stiffer lock-up spring. We installed the new spring, turned the main line pressure up one turn on the screw and change the fluid. That trans now locks-up at 46 MPH with no shutter. The maker of the stiffer L-up spring said that it would increase the L-up point by 10 MPH but we only got a 6 MPH increase in our application.  DD |
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| Author: | Reed [ Mon Apr 19, 2010 3:35 pm ] |
| Post subject: | |
Thanks Doc! The behavior of the transmission makes me suspect it is lock-up related, so I think I will focus my attention on that system. |
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| Author: | SlantSixDan [ Mon Apr 19, 2010 3:58 pm ] |
| Post subject: | |
See this post and I would definitely shim it with some ring washers in a truck/van application. I would want to shoot for a lockup speed of 50 to 55 mph. |
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| Author: | Reed [ Mon Apr 19, 2010 4:53 pm ] |
| Post subject: | |
Thanks Dan! I'll try finding a stiffer spring and figuring out how to shim it. What I shim and what I shim with is still unknown to me, but I will spend some time with a FSM and google and hopefully figure it out. |
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| Author: | D-Ram 1596 [ Mon Apr 19, 2010 6:17 pm ] |
| Post subject: | |
Well my truck must be off too, because it locks up at around 35 also. Unfortunately it hasn't been hooked up since the lean burn was replaced. |
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| Author: | Reed [ Mon Apr 19, 2010 7:07 pm ] |
| Post subject: | |
OK! I cracked my Factory Shop Manual and located the "lock-up" spring on the valve body. No sweat. I don't even have to pull the transmission to replace it, just the valve body. Whew. Incidentally, I found this smilie on another board and thought of you, Dan.   So, my brother is going to try and get one of those stiffer lock-up springs from the dealer and we will hopefully install it this weekend. Now, as far as shims go, I am assuming that the shims would be washers that go on one end of the lock-up valve? Presumably the end opposite where the spring goes? Anybody have experience with shim thickness and effect on on lock-up actuation speeds or is it a guess and try proposition? |
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| Author: | Doc [ Tue Apr 20, 2010 10:05 am ] |
| Post subject: | |
Go get a TF-TC "shift kit" from Superior Transmission. http://www.superior-transmission.com/Pr ... .cfm?ID=44 On ebag for $40.00 (shipping included) Use P/N: KTF-TC to search for other online sources or find a local distributor. This kit gives you 3 different lock-up springs, along with some other nice info to help a Torqueflite shift better. These lock-up springs are somewhat stiff and install into a small space... it is hard to get the correct tension by shimming or stretching the stock spring. The stiffer springs are much stronger, with thicker wire size. DD |
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| Author: | Reed [ Tue Apr 20, 2010 10:06 am ] |
| Post subject: | |
Anyone have experience or opinions with or about THIS spring kit? |
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| Author: | Reed [ Tue Apr 20, 2010 10:07 am ] |
| Post subject: | |
D'OH! Doc beat me to it! Since i have a recommendation, I will give that kit a try. Thanks! |
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| Author: | Bren67Cuda904 [ Tue Apr 20, 2010 1:09 pm ] |
| Post subject: | |
I was told by a very good tranny builder that those kits have a tendency to lose there spring "stiffness" over time and heat cycles. I guess maybe there spring steel is cheap and or made in china. |
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| Author: | Reed [ Tue Apr 20, 2010 1:13 pm ] |
| Post subject: | |
Well, I am fairly sue that the spring in the transmission right now has worn out, so if a new spring fixes the problem then (a) I have determined what the problem is and (b) I can track down a better quality spring if and when this new one fails. |
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| Author: | Eric W [ Wed Apr 21, 2010 1:52 am ] |
| Post subject: | |
Intresting..the trans in the 5th locks up at around 35-38 mph...kind of a pain when it locks up under moderate acceleration. Let me know how it goes Reed..Looks like something I want to do in the future. I raised the line pressure and it helped firm up the shifts over stock, as did the adjustable kick-down rod. I think that van will be fine with either a smaller cooler or the stock one. Even with the small cooler on my Satellite, I could still feel the cooling lines are cool to the touch after a long drive. |
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