Transmission issues... fluid?

My 95 is mostly original, and only 155,000+ miles. 2.7/5-speed/4WD.

Lately I noticed its a little hard to shift. Doesn't grind, but just takes effort to slip into first gear (that's when I notice it the most).

Original clutch
I replaced all the clutch hydraulics (master/slave, hardline and hose).

Engagement is in the middle of pedal travel. I can lift the pedal off the floor (running, in gear), and the truck doesn't start moving until I am an inch or two off the floor. Clutch seems to hold fine.

But even with the clutch all the way on the floor, its still a little difficult to shift into 1st gear... When moving the shifter forward, I can "hear" a slight "knock" when trying to move shifter into 1st but before actually going into 1st... Like I am in neutral and its just not going in to first without some effort (not too bad, just noticeable, not like butter). But absolutely NO grinding...


When I inherited the truck in early 2021, I changed all the fluids. For the transmission I THINK I used Valvoline (75W90?) that was rated for GL-5 and GL-4. My receipts show I bought 5 or 6 quarts of the Valvoline, and 1 quart of Lucas Synthetic 75-90. From my other cars, I recall GL-4 was for "yellow" metal synchros...

But now reading the label on the Valvoline gear oil bottle (I swear I read before buying), it says GL-5 (for hypoid gears/differentials) and GL-4 for "non-synchromesh" transmissions...


I changed the front and rear diffs, the transfer case and the transmission oil.

I know I didn't mix the oils, and pretty sure the trans takes more than 1 quart (can't find my manual)... Although I might have had some more Lucas from my other car projects.



Uh Oh...

What gear oil should I run in my transmission? Thinking I may drain and refill just to be safe... I hope its not too late.

 

I mean, as much as you're stressing on gear oil... I'd suggest it's probably time for a new clutch. 28 years is GOOD run.

 

Yup. Replace the shifter bushings, fill the trans with Redline MT-90, and do the clutch.

 

I will change the fluid, and possibly look into the shifter bushings...

Replace the clutch? Probably not, as it doesn't seem to be an issue. It grabs/holds fine, and release is mid-travel for the pedal...

 

How is your suspension? Shocks etc? Have they been replaced recently or ever?

 

I too would vote to also change the clutch. I had similar experiences in my '97 - at around 360k miles and as far as I knew was the original clutch that was engaging just "fine"... until it didn't anymore and left my son stranded and me having to go tow him home in the middle of the night. Upon pulling the tranny there was nothing left of the clutch but the fibrous material all over the housing. At 28 years, its due and worth the piece of mind I would think.

 

???

I know that shocks and suspension have absolutely nothing to do with the clutch/transmission…

suspension is great, bushings and boots all look good, lubed everything ( plus my brother maintained the truck well). Shocks were replaced with Bilsteins. U-joints replaced (double-Cardin was inspected and lubed), driveshaft center carrier bearing replaced. Brakes flushed and new flex hoses.

None of that is the problem.

 

Did you know that your original suspension and your replacement Bilsteins have a life span of around 50k. Sure you can keep driving around on them, but they're toast. The point is, just because something isn't outright broken doesn't mean it's not underperforming and warrant replacement. Your clutch is a wear item just like the shocks and pretty much every rubber item on the truck. You can say their good and fine, but at 28 years old, it's time to replace all that.

 

L78 (375HP),
I would suggest Marlin HD shifter seats Heavy Duty Seats | Marlin Crawler, Inc. and Redline MT-90 in the tranny. I have inexpensive Lucas dino oil in my rebuilt R150F tranny now for break-in and it is working well. Your clutch/your truck so your call on that. Best of luck!