coughingskunk

Hey everyone, I'm new here and just bought an 87 pickup SR5 4wd from my buddy. Truck has 140xxx miles on it and in relatively good condition (or so we shall find out in the weeks to come).

It was leaking some oil from the valve cover and leaking some brake fluid from the clutch master/slave cylinders (both original) so I replaced both of those as well as the flexible clutch line and the clutch slave cylinder. No more motor oil and brake fluid leaks Also adjusted the valves while I was in there. There is however a bunch of grime all over the transmission and transfer case and I can see some seal replacements due in the future.

To qualify myself from those thinking that I don't know what I'm doing (and who will undoubtedly tell me I bled the clutch line wrong) : I have rebuilt two xs650 motors from crank up bored out to 700cc and built the associated motos from ground up with frame mods, brembo brakes, etc, replaced the motor in my old 91 civic hatch with a b18 and matching si trim tranny, bagged a 2wd sonoma and tucked 18's under it so I could drag bumper and just recently did a clutch/flywheel/pressure plate replacement on my audi 2.7t. Also a bunch of other crap you probably don't wanna read about. Basically at this point in my life I have a full garage short of a lift.

I have the entire service history of the truck in writing as it was in his family and well maintained up until about two years ago when it became a camping/weekend only truck. There was a new clutch/flywheel/pressure plate put in about 1500 miles ago. There is no mention of the pilot bearing, which I've been reading may be an issue. Is there a way to check without pulling the tranny? Some sort of whining or other indicator?

My issue is that shifting into first from a dead stop is near impossible once everything is warmed up. It feels like 1st is just gated off. Blipping the throttle does not make it any better. The only way that I can get into first from a stop are by shifting into another gear and then first and on the rare occasion it will just work. I will mention that 2nd gear feels like that around half of the time when I am attempting to put the tranny into a higher gear then back into 1st to take off. 3rd, 4th and 5th never have any issues while doing the trick to get into 1st. Also, no issue going into reverse other than a slight grind that I feel is reasonable.

No issues while driving at all. Everything shifts great, no clutch drag, no grinding between gears, no issues with lockouts. I can even shift back into first while coming to a stop without issue. My problem only arises when going into 1st gear from a dead stop. My buddy said that this is how the truck has driven ever since he purchased it form his grandpa.

Another bit of info is that I can hear a slight thud when I take the truck out of gear while slowing down and then placing the shifter against one of the gear gates before any grinding occurs. It is not loud but there is definitely something moving in the driveline. No sure if this is a related issue, or common.

Below is the list of things that I've done/checked already:
- New master/slave cylinder and clutch pedal adjusted to FSM specs. Feels great, and have confirmed that the slave cylinder has full throw.
- Pulled the shift bushing and it looked basically new. The black part at the bottom of the bushing had separated. Either way I bought a new bushing/seat and seal deal from Marlin that will be here later this week. There isn't a ton of slop in the shifter so I'd be surprised if this fixes it.
- Transfer case and tranny are on the low side of oil. No gushing leaks (no drops of anything under the truck) but there is some wetness underneath. I will change the fluids later this week once the parts from Marlin come in and see if that helps but I don't think it will.

Given the above novel, I've got the following questions:
Would this problem be due to a bad pilot bearing? Synchro? Shift fork?
Why is this happening only when the truck is warm?
Why can I put the tranny into another gear then first without issue?
What do I need to check and in what order to diagnose this? This is not a DD at all and I can take things apart and let them be for a while if needed (such as while rebuild the tranny, etc).

TL;DR: Truck shifts fine from a stop when cold. Truck won't shift into first when warm unless the transmission is put into another gear first. Need help.

Thanks erryone and sorry about the novel.

arlindsay1992

iTrader: (8)

Look up clutch pedal bracket fatigue. It's fairly common for our trucks and causes the clutch to not disengage entirely thus dragging slightly and still transmitting a bit of torque to the transmission input shaft. Repair requires removing the pedal bracket and weld repairing the crack or replacing the assembly.

If your pedal bracket is broken then it will cause the clutch to not fully disengage thus still transmitting a bit of torque to the transmission input shaft. First gear syncro takes a lot of abuse even normally. When shifting into first gear at a stop it must slow the transmission input shaft from engine idle speed to zero RPM to match the wheels. When downshifting into first as you slow down it needs to spin the transmission input shaft from whatever RPM in second to whatever RPM you need to be in first gear at the same speed. Since the difference in ratios between first and second gear is the greatest it means the syncro is doing a lot. All other syncros only make up the mismatch of a few hundred RPM between gears.

What you are doing when you shift into any other gear from a stop is using the other syncros to slow the input shaft from engine idle RPM to zero. The other syncros don't take as much abuse so they easily stop the transmission input shaft from spinning despite the dragging clutch still trying to rotate it. Once the input shaft is stopped then you are able to shift into first since the syncro no longer plays a role.

Reverse is not synchronized so if you press the clutch in immediately slowly bring the shifter into reverse you'll hear grinding. This is the actual gear teeth slowing the input shaft to zero RPM so that the gears can mesh. This does no damage and is normal. Many transmissions used to have non synchronized first and reverse.

coughingskunk

No kidding.. just looked at the pictures over in this thread. I'll check when I get home..

coughingskunk

Grad school and a girlfriend sure seems to eat up most of my time... Finally got a time to check out the clutch pedal bracket.

Turns out it wasn't the clutch pedal bracket. Sat under the dash last night cycling the clutch with no bracket movement at all.

Still waiting on the parts from Marlin as they won't arrive until saturday and will likely install those parts and change the tranny and tcase fluids and shoot grease through all the zerks at that point. I crawled around under the truck last night and confirmed that I will be replacing the seals on the tcase in a couple of weeks. The seal on the back of the tcase is on its way out and leaking pretty good.

Will report back next week with hopefully some good news!

millennium falcon

My truck does this sometimes too. I usually have to put it in second gear and let the clutch out a tiny bit until the truck moves a little then it will slide right into 1st. I have no idea what it causing this.....I know my tranny has high miles and lots of abuse so I''m guessing it is worn or out of alignment or something.

TransAmBandit

You said the clutch pedal is adjusted as per FSM. But is the clutch rod adjusted properly?

coughingskunk

Are you asking if the pushrod is adjusted properly? If so, then yes. Correct free play and engagement point per the FSM.

coughingskunk

New shifter bushing and seal/seat are in place and there is absolutely 0 positive difference in the feel of the shifting.. In fact, now the shifter doesn't like to go back into the neutral position when pressing the stick to the left side of its movement. It snaps back from the right extremely well, but just sticks to the left hand side when placed there.. Could I have a bad centering spring (or whatever it would be called)?

I can however now get it into first if I place the shifter on the gate for 1st gear and then slowly, without force, slip it through the gate. Small but noticeable difference.

the_supernerd

New fluid will probably help. If you have not already changed the fluid, try using some Redline MT-90. People speak very highly of it, especially on these trucks. I put some in my '05 Tacoma, and it seems to help the syncros hook up faster. It sounds like you have checked almost everything else I can think of.

What brand of master and slave cylinders did you use? I have noticed a difference in pedal feel between a lot of the no-name brands and the AISIN cylinders. Even though you adjusted the pedal to FSM specs, you can try adjusting the pedal a small amount both ways to see if that helps as it is easy enough to try. The aftermarket cylinder might need just a bit more pedal travel or something as the pistons might not be to exact factory specs.

My '87 4x4 has had trouble getting into 1st at various times over the years, especially if I try to shift it in right after I put in the clutch. It helps if I wait a few seconds with the clutch in before I shift into first. Now that I am thinking of it, the problem does not seem to be as bad as it used to be. I now have both an AISIN master and slave cylinder, but still the original clutch, transmission, and shift seat bushings with 226k on them. I probably have about 10k miles on the gear oil, which I think was Valvoline from the parts store. I do remember having a problem finding the viscosity and grade of gear oil that the manual calls for. Maybe someone put too thin/thick gear oil in yours or something like that? If I remember correctly, it calls for GL-4, and I could only find GL-5.

coughingskunk

In the recent tranny oil change I put in Amsoil 75w90 GL4 gear oil. Can't get MT90 locally and oddly enough, the only place I could find any GL4 spec oil was at the tractor supply store.. A deer crashed into my friends 08 taco and he has been driving my 87 literally since I changed the oil while waiting for the repair shop to fix his truck. I will say that getting into first has gotten slightly easier since the oil change.

I used AISIN master and slave cylinders for replacements of the original AISIN parts. I am going to try adjusting the clutch pedal so that it disengages the clutch higher in the stroke and see if that has any effect on the ability to shift into gear.

Who knows though. At least at this point I can get it into first without needing to shift to 3rd/4th then back into first. I've got next week off from school and will be pulling the transfer case to replace gaskets and seals since its leaking a bit, so maybe I'll uncover some other piece of the puzzle then.

the_supernerd

Sounds like you have the right fluid, and the correct parts, so the only other thing I can think of is the pilot bearing or the syncro. There is a chance it will get a little better after some miles on the new fluid. Good luck!