- This topic has 6 replies, 5 voices, and was last updated 11 years, 6 months ago by
.
-
Topic
-
hello , I have a 93 chevy pickup, with the 4l60e and the issue is its not gone into 4th gear a couple times on me
some background on this truck, 203,000 miles, tranny was rebuilt at 130,000
this truck has always had and engine overheating issue in traffic especially on hot days or when pulling a trailer, even a small flatbed trailer with a couple wheelers on it, I had replaced the radiator, water pump, thermostat (a few times), added an electric fan, new fan clutch, that was all about 3-4 years ago, finally tried a new fan clutch a couple weeks ago and it seemed to do the trick for that (bad new fan clutch originally I guess)
and another thing I should add, about a year ago the TCC was not locking up all the time, it seemed as tho I could hold the brake pedal out with my foot a bit and that would let it lock up however as dumb as it may sound I get about 13 mpg with this truck average, on the highway if I can keep it above 2000 RPM (75 mph)I could get about 17-19, so without the lockup at 60-65 im just into the 2000 range and getting 15 average, so basicly I sluffed the TCC switch off for that reason
1 other noted detail is only 1 time pulled onto an exit ramp to the highway and the truck stayed in 1st gear till I let off the gas at about 45-4800 RPM, only happened 1 time tho about1.5 years agoso that’s the basic background
so the present time:
the other day it was ungodly hot out and I was pulling a pretty heavy utility trailer with a full load of stuff, engine got a lil bit over 210 but the new fan clutch seemed to be doing the trick basicly helping someone move so not like I was pulling a truck but id have to guess a couplefew thousand pounds maybe, basicly all during rush hour so the truck was doing great, but after maybe an hour and a half it downshifted into 3rd and would not upshift again, so got to my buddys, we unloaded and I drove home pulling the same trailer but empty and no probs, everything was working like a charm, next day making the same run, but no traffic and paying much more attention to the tranny no issues till about to my buddys place and I hadn’t moved the accelerator a bit and was keeping the tranny in 3rd much more (my attempt at being more gentle) but it downshifted and no 4th again also incredibly hot humid and nasty out, got it unloaded and drove home without the trailer, not a single issue, next day no issues, but no trailer and a lot less miles
talking with a buddy we kinda thought maybe a 4th gear shift solenoid?, maybe heat related, pretty sure its partial atleast heat related…
1 thing I did notice is when I lost 4th and it would go to 3rd if I let off the gas the RPM would seem to drop and if it was in neutral….that’s possibly normal but I don’t know jack about trannys, and stopped caring about the time computers got involved with em. ive seem some stuff about the 4l80es having temp sensors and stuff but as I recall the 80s are basicly computers controlled 400s whiles the 60s are 700s, but thats about as far as my knowledge goes and my buddy is great with TH350s, and knows 700s pretty good, hes rebuilt a few but is no guru whatsoever…… any help/advice would be greatly appreciated
-
Replies
-
When towing, especially if it is a HOT day, you should have a external cooler installed. Who knows what’s happening to the fluid alone inside.
It might be a good idea to change the fluid in case it’s been overheated.
As mentioned check the trans fluid. if not burnt nor black I would change it. would also change the shift solenoids since the pan will be off and they are fairly cheap. test the vss for proper operating range , also check the tps as it is tied into the ecm and does effect shifts.
checked the fluid level, seems ok possibly just a tad overfull, but definitely smelled burnt, it looked decent color wise but ill look again tomorrow when I have more light just to double check
I understand the temp sensor will put this trans into lockup if it starts to get hot as a means to cool it down. You might have issues with one of the temp sensors or the TCC solenoid. This is common stuff for just about any electronic transmission.
You also mentioned the brake pedal, the switch also kicks out the TCC solenoid. Someone else mentioned the TPS and those are a known failure with GM trucks. If the fluid smells burnt, you may have a cooling problem with the engine in addition to the lockup issue. Remember, for every 20 degrees past 190 in the tranny, it shortens its life by half.
I send my ATF to Blackstone labs and have them work up a report for oxidation and wear metals. If its dirty, you can also particle count the fluid. Since you are towing, you need to run synthetic fluid for better heat transfer and reliability.
Allison 1000 requires synthetic fluid to remain in their warranty. It just shows that the manufacturers recognize the need for synthetic oil in their equipment.
- You must be logged in to reply to this topic.