bjafeman

My 91 I-6 4 speed has about 120K on the clock and has a funny gear grinding issue I have a few questions about.

Problem:
If I go to shift into first or reverse when everything is cold (i.e. first start of the day or within a few miles) the transmission engages smoothly. No grinding or anything like that, even if I repeatedly use first. After the truck is warmed up, however, first and reverse will grind before engaging. 2-3-4 are all smooth enough regardless of temp.

Since I have a granny gear, it's not usually a big deal to skip first, but Reverse is annoying....people look at me like I'm an idiot, and since I seem to do plenty of other things to justify this I'd like to at least eliminate one.

My questions:

1) Bad synchromesh? If I'm hauling a load and go to second, then first at a dead stop, there's no grinding.

2) Would heavier or lighter oil help?

3) Do I have the Borg Warner T-18? It has a PTO.

4) My clutch is probably going to need a replacement in the next year and I'm brave enough to do it in my driveway. T-18 seems somewhat tankish and simple. Would it be worthwhile to rebuild/replace the trans then too, or is that kind of work best left to those who turn transmission wrenches for a living?

my92

I don't think it is Synchros I think your clutch is going faster then you think.
These transmissions use mercon ATF so lighter or heavier oil won"t help.
I think the T18 was used up 1984....don't quote me on that.
Find the tag on the trans that will tell all...the door jam may not be reliable if the trans could have been swamped.

Ham-Bone

my tranny did the same thing for about two weeks then guess what i now need a clutch lol it sucks

Just call me Sean

iTrader: (1)

These trucks had a recall for firewall flex. Over time when you push the clutch the firewall would separate and push out, putting additional room between the clutch master cylinder and clutch pedal. This causes the clutch to not fully release and the grinding. It may take a few times of pushing the clutch before the metal of the firewall heats up and moves more than when colder. My truck did the same thing, it would be better when cold. Have someone push the clutch in repeatedly while watching the clutch master cylinder under the hood to see if it moves out.

Just call me Sean

iTrader: (1)

Also, 1992 and earlier 4 speeds used 80 weight gear oil.

my92

I defer to the master...good looking out sean...I do remember that recall now that you mention it. Sorry about the ATF (one thing and man can always use more of.
Alcohol, tobacco and firearms). I thought they stop using 80 weight in 1990.
Saved that man his trans..I have the right to remain silent...I think I will use it. ;=)

bjafeman

Interesting to hear the firewall flex. I've thought that if felt like I had to push the pedal farther sometimes when things warm up. Wouldn't be surprised if it was a combination of the firewall and the clutch wear. Will check for firewall flex.
Thanks.

strangeling67

Huh mine does the same thing, no problems when cold but then after a little driving 2nd to 3rd crunches ? I'll have to check on the firewall flex as well !