Engine/Transmission (1994 - 1998) 2-stage upshift into OD?????

[gilgle]

This is my first post, so please bear with me. I have noticed since I got the truck that when it shifts into OD, it shifts with a drop of about 250 RPM, then about a second or two later, it shifts the rest of the way with another drop of about 300 - 400 RPM and a very noticeable increase in power. transmission fluid/filter changed 500 miles ago. TPS reset via battery disconnect/reconnect. No change. Any ideas?



Thanks in advance,

Glen

 

[BlakeDavis]

I think what you are seeing is the shift to OD and then the torque converter locking up, which is a good thing. Dont think it is anything to worry about.

 

[Bart]

Welcome Glen. If you are experiencing this at about 45 mph then Blake is right. First the o. d. shift (4th gear) then the torque converter locks up. It is normal. If your rig doesn't have gauges "GET THEM"! Watching the trans temp while climbing almost any hill under that 45 mph lockup mark sends the trans temp through the roof (250*+). Exhaust temps are another reason to have the gauges. You can drive the exhaust gas temps (egts) through the roof again (holy roof isn't it), by lugging the engine. The engine spinning faster than 1700 rpms is where the power curve starts. The gauges will educate you more than anything else, except this site.

 

[gilgle]

Thanks for the info, guys.



The shift point seems to depend on the amount of throttle. It generally doesn't want to shift until I get to about 50 mph and around 2000 - 2300 rpm if I am on the highway. It hangs there sometimes until I ease off the throttle; other times it shifts on its own.



So, the gauges are a good idea even if I don't plan on major HP upgrades?

 

[sleon]

2 stage upshift to od

Hi gilgle Having the same type of problem. Mine gets up to 60-70 at 1700 and jumps to 2000 rpm then back, thenup to 2000 again. Changed fuel filter and that helped,but still does it only not as much. 94 12 valve auto,300,010. I know, what am I crying about. original trans. Sleon

 

[Joe G.]

gilgle & selon,



Your transmissions are 47RH with a mechanical governor. Some of the later stuff about transmissions does not apply to the way your transmission behaves. The '96 and up use a 47RE with an electronic governor. However, the TPS behavior is about the same. Shift OD and lockup shift points are adjustable but you have to modify the TPS circuits a bit. The TPS is just a variable resistor so disconnecting the batteries has no affect on it. I don't think the behavior of the PCM regarding the transmission will be affected by disconnecting the batteries either on the 47RH equipped trucks. This situation has been discussed for quite some time on this forum. Do a search on TPS on this forum. Especially posts by Howard Durand and ridesamule. There is a lot of information there and a lot of posts to be prepared to read a bit.



The post above by Bart is right on. Get gauges. Don't lug the engine. The transmission depends on pressure to work right. Pressure depends on RPM so if you lug it you are putting more strain on the transmission than you really want.



Sleon,



Changing the fuel filter will NOT affect transmission behavior. That has absolutely nothing to do with how the PCM deals with the signal from the TPS to cause the torque convertor clutch to lock and unlock. The jumping to 2000 RPM is controlled by the TPS. You need to fix that before it tears something up. Do the search and read the posts about it.

 

[gilgle]

Thanks for the info, Joe. I have been reading about the TPS adjustments. I'll get the voltmeter out and take a look. Thanks again!