Join Date: May 2010
Location: Cordelia, CA
Petroworks transmission and clutch replacement and first thoughts
When I purcheased my 88.5 Samurai 3 years and 40,000 miles ago, it had a new clutch in it, but a noisy transmission that would not downshift into 1st or 2nd without double-clutching.
I thought it had a stock clutch, and I babied it accordingly, but one time while making a very steep climb from about 8,000' to 10,000' up the side of a mountain, I had to slip the clutch pretty bad to get moving, got it smoking nicely, and it has never been the same since, though it still worked fine. I found out after removing the transmission that I actually had a CenterForce Stage One clutch.
A while back, the transmission started making grinding noises in every gear but 4th. I wasn't confident to rebuild the transmission, so I decided to go with a Petroworks rebuilt one. I also got a "big bolt" shifter to go with it, and a Petroworks HD clutch.
The "big bolt" shifter just has a bigger shift locator bolt to last longer and I believe they machine the shifter ball notch to fit it. I figured while I had the shifter out, it was a no-brainer to do that.
The Petroworks HD clutch disc has a ceramic compound friction material on one side, and bronze "pucks" on the other. It is built specifically to be slipped to the point of abuse without slipping or failing. The Petroworks pressure plate is a simple diagphram type.
I wound up with a pre- '88.5 transmission which has the taller .795 overdrive gear, vs the .865 ratio of my original transmission.
I found that replacing the transmission was not as difficult as I expected. I have not done a transmission replacement in over 10 years, so was a bit nervous about it.
The first thing I did was put the front wheels up on ramps and drain the oil from the transmission then let it sit overnight to get as much out as possible.
I then pulled the passenger seat, front carpet, shifter boots, and shifter. I also removed the shifter tower from the transmission.
I wrapped some carpet padding around the distributor to protect it and the firewall from each other.
I removed the Thorley header and the cat to make more room. I also unbolted the front drive-shaft from the differential, but did not remove it. I removed the air filter box to have better access to the starter. I then detatched the clutch cable from the transmission. After un-bolting and removing the transmission mount, starter, dust cover, intermediate drive-shaft, and the four engine to transmission bolts, I pulled the transmission free, and found I had to turn the transmission sideways to get it to clear the clutch.
At this point, the bell-housing caught on one of the weights on the CenterForce pressure plate diagphram spring. I had to use a pry-bar to pop it lose. When it came lose, I was lucky to not hurt my fingers between the bell-housing and floor. I think if I do this again, I will place a box underneath to catch the transmission well off the floor or maybe some motorcycle tie-down straps across the frame rails.
After removing the clutch, I stuffed bread into the pilot bearing hole, and pounded a bolt into the hole to remove the pilot shaft bearing. You just pull the bolt and keep feeding bread in, until the bearing pops out. I like this method much better than using grease, as it is less messy, and I feel more reliable as the bread does not ooze out like the grease does. The bread turns into something like play-dough, and is very easy to clean up.
I did not like the Chinese bearings Petroworks sent, so I went to Napa to get Japanese bearings. The Chinese pilot bearing was not smooth rotating like the Japanese bearing was. The throwout bearing seemed ok, but you never know... The price should have clued me in to the quality of their bearings, but I figured they had just gotten a good deal. I find it hard to believe they ship such a high quality clutch with low quality bearings.
I moved my 88.5 gear switchs from my old transmission to the new one, with no problems. Thanks go out to BillJohn for letting me know they were compatible.
Getting the transmission back in was harder than getting it out. I have read that it is easier if you notch out the transmission mount, but had also read that you don't have to. I did not. I did find that I had to remove the shift tower to be able to rotate the transmission to where it would slip up past the clutch. I also used a pry-bar to aid in this. I do not believe I would have been able to get the transmission back in if I had used a CenterForce clutch, without notching the transmission mount.
After that, everything went back together smoothly. Since I had the shifter out, I filled the transmission from inside Sami, which was nice.
At this time, I went ahead and pulled all the seats and replaced the carpet.
After everything was back together, I found that I had a lot of extra slack in the clutch cable. It was well within the adjustment range though.
Over the weekend, I drove it 200 miles. I find the Petroworks clutch to be lighter than the CenterForce one. It also does not feel heavier when shifting at high RPMS, something I did not notice until it wasnt there any more. At first, the Petroworks had a very narrow friction zone, but either I got used to it, and/or as it has broke in, it developed a wider friction zone. I killed the engine several times getting used to it. The friction zone is still a bit narrower than before, but it is certainly no "on-off" switch either. I am very happy to have a clutch that is built for abuse, and feel knowone would have trouble getting used to it. The lock-up is firmer than the CenterForce Stage 1 ever had, but it retains springs so it should not hammer the drive-line. I do feel a bit of chatter when slipping it at low throttle settings, and have read of this in another review. It is not bad, and I can live with it.
I noticed that the shifter is more precise than before. The old shift locator bolt showed almost no wear, and I had not noticed it getting sloppier. The old shifter bushing was poly and in good shape, just like the new one. I figure the innards of the rebuilt transmission are probably tighter, and the notch in the old shifter probably had wear. The main area I notice this is when shifting from 5th to 4th. I used to be able to snick it directly from one to the other, but now have to let the shifter center itself before pulling it back to 4th. I'm sure I will get used to it, but right now it slows my shift down. No biggie...
The rebuilt transmission is very quiet. I hear some low volume normal whirring and a low volume whine that sounds kind of like radio static. The whine may be from other parts though and is so quiet as to not concern me. I had no clue just how noisy my old transmission was, even when it was working ok. I thought it was normal.
The taller 5th gear is very noticeable with the stock 1.3L engine. Almost any up-hill run now requires a downshift, and you really need to be up to speed before shifting into 5th, as the acceleration is down to a crawl. I really like the taller 5th on level ground and down-hill runs. Before, I did not normally cruise above 65 or so on the freeway. Now I cruise at around 70, and let it climb to 75 on the downhill stretches. That doesnt sound like much, but it is just enough to make it worthwhile to me.
The shifts still have a kind of a notchy feel if you try to rush them. I'm not talking about slamming the shifter. It's more of a snick-snick, instead of a snick....snick. I had attributed it to worn syncros on the old transmission. Maybe the new syncros need to break-in, or a different oil will help, like Redline MT-90. I am breaking it in on Lucas conventional 80W90 though. It might just be normal for a Sami trans. The shifts dont make any noise when the notchiness is present. It is strictly a feel thing. I try to slow down my shifts so it stays feeling smooth, as I feel this will contribute to a long life.
Sami just keeps getting better and better.
'88.5 Samurai JX, mostly stock