ok guys got a 95 blazer with the two piece bellhousing and the old vortec motor OBD2. so when I first got it the tranny was shifting fine when cold but when it got hot it would shift really hard into 2nd and 3rd. almost chirping the tires if I floored it. so I changed the filter and fluid. put 1qt of lucas trans fix and about 4qts of dex 3. seemed to have stopped the hard shifting when hot but did it when cold. also my rpms at 55mph is 2100. that's too high. but after about a week and fixing a vac leak the rpms went down to about 1700 at 55. anyway so I thought well get another 4qts and change it again. so took it for a spin this time without adding lucas to it. now its hard shifting all the time hot or cold and my rpms went back up to 2100 at 55. but if I put my foot down a bit more on the gas the rpms will go up then back down to 1700 ish... then let off the gas a bit to get to 55 again and rpms are up to 2100 push pedal down a bit they go up then down to 1700 ish.
fluid is at proper level
has brand new tps sensor
all vac leaks fixed
doesn't slip drives great just hard 1-2 and 2-3 shifts sometimes the downshifts are kinda harsh but not bad.


im thinking about getting another 4qts and a bottle of lucas trans fix and do it again. the transmission fluid before doing anything to it was a dark brownish red. didn't smell burnt just looked spent. also there was no debris in the pan just your normal clutch wear on the magnet.


what do you guys think I should do.

 

ive read a lot on the these forums and tried to reseat the computer connections and disconnected the battery for a while and it still shifts hard going into 2nd. but now it seems to be ok after warmed up a bit but still a little hard but not much. also it shifts ONLY after 15mph but less than 20mph. all the other blazers and jimmys, bravadas, ive drove shift at 10mph.


also ive read that it can be the engine coolant temp sensor. not the gauge sensor but the computer one.


what do you guys suggest, thanks

 

It could also be worn shift solenoids or the TCC solenoid. Being a 95 is it OBD 1.5? Are there any trouble codes stored? Search for code P1870 in the tech section. That's an OBD2 code, but your symptoms sound very similar.

 

the computer is OBD2. I just verified that today with my laptop scanner and all the sensors seem to be reading fine except one or maby. the map sensor is outputting 5-7 psi on the scanner at idle when cold 25 degrees out and hasn't been started for 5 hours. I also changed the map with a different one a while back with no change so idk.....????


the engine is the old vortec model with the cpi injection with vortec plate on top with old 2 piece bellhousing transmission .....


also no codes at all....

 

well I was out on the highway again today and the transmission stayed in lockup the whole way there 12 miles at 55mph 1650 rpm
but on my way back it was at 2100 rpm at 55 but I put my foot down on the gas a bit more and rpms dropped to 1700 ish and stayed there. then few minutes passed then 2100 rpms again so gave it some gas then back down to normal.
shifting into second and third is getting a bit softer but not normal
when I first got it, it looked like the transmission was never serviced. pan gasket crumbly and dip stick tube rusted solid in place, and fluid was nasty but not burnt smelling.

 

here is a video of what its doing. I didn't get on the highway but just to show you the shift points of 2nd gear.

 

anybody else have any suggestions? it seems to get better with time but just for other people that see this I just replaced the fluid 2 times. 2 gallons of atf. and one bottle of lucas trans fix. I swear by lucas trans fix as I have used it on a slipping tranny in a 94 s10 blazer and it worked for 2 years till I sold it. then again I put over 3 bottles of it in there lol. 3qts. im going to have this trans rebuilt in a few months but just wanted to see what anybody else had to say about it. thanks

 

well I pumped out 3 qts of fluid and put in 2 new qts of atf and another bottle of lucas trans fix. now the tranny stays in lockup on the highway at around 1600 rpms give or take 50. but it still takes it time and shifts hard into 2nd when cold. going into 3rd is fine now. im still gonna have the tranny rebuilt within the next few months.

 

El-Beautor is correct. Your 95 with CPI, (CMFI) is in fact OBD1.5 and it is not fully OBDII compliant. To be fully OBDII compliant, there must be oxygen sensors on each bank so the PCM can control fuel mixture for each bank seperately, CMFI does not. Your injector is "batch fired" which means when it fires, it sends an equal amount of fuel to each cylinder, each time it fires. Very few late production 95's had CSFI. All 1996 and newer had CSFI which is fully compliant OBDII.

What you're experiencing with shifting, is most likely a worn valve body in the transmission. The spool valves bind up in their bores and when line pressure increases, it forces them to move, and the shift is harsh. There are no "fixes in a bottle" for this problem If the trans has never been serviced, there may be a build up of crud in the valve body causing the spool valves to stick. Either way, provided the rest of the trans is OK, replacing the valve body should take care of the problem.

 

yea im just gonna have it completely rebuilt so I don't ever have to worry about it again. but obd 1.5 actually does make sense now because I can read every sensor with my scanner but the bank 2 sensor 1 o2 sensor. but I can read what bank 1 sensor 1 is doing. hmmm. but if it was 1.5 then why can my computer connect to it if it only supports obd2? and it stores PO codes cause I got one awhile back that was for the evap. but yea I can see it being 1.5 though because it should of stored a tranny code that po1870 when it wouldn't stay in lockup on the highway. but never did. thanks for your reply.