- Location
- Fort Irwin, CA
Gentlemen of the SEC! I'm back for a bit and trying to get the Blurple in proper shape before I stable it for two or three years. I am going to a new post in South Korea and the Army won’t ship cars there. I don't want to come back to the US and immediately have to work on the jeep. I need your wisdom.
I know this is long, but I'm trying to get the detail questions out of the way up front.
- problem -
The problem is that I was having a really hard time getting the trans in gear (AX-15) sometimes especially when stopped. First gear required a lot of hunting for Fourth or Second and Fifth and then I could catch First. This is frustrating spending three or four seconds doing this at every stoplight - though I could usually get the jeep in First at a slow rolling speed that meant holding the clutch in for the whole time the light was red and eventually that'll ruin the throwout bearing.
I took the jeep to a local shop in Lawton, OK and they separated the engine and trans and supposedly the pilot bearing just fell right out of the back of the block. They replaced the pilot bearing with a poly bushing (much like the 258 ci engine takes) and the problem was fixed for a while, but it has reared its ugly head again in exactly the same way. I have a Hurst short-throw shifter on the trans which I am sure is exaggerating my problem, but I don’t think it is the source as the issue comes and goes mysteriously. I’m removing it shortly to compare how it feels with the old stocker.
- background / other info -
The jeep is a 1998 with a Russ Pottenger-built 4.5L stroker made out of a '96-98 block, and the original AX-15 rebuilt ~17,000 miles ago. I have been chasing vibrations on and off, and I keep wanting to blame the vibes on the engine because they're bad enough that I’ve lost two fuel rail bolts and the rear header/manifold bolt keeps backing out and my exhaust downpipe flange bolts keep vibrating loose as well (with new exhaust hangers). I also had to change the rear main seal twice since the engine swap and it looks like the new one is seeping almost immediately.
The engine is largely smooth at idle but using the A/C brings on a nasty vibration that I'm still trying to understand, and I am wondering if something is off in the balance of the engine internals. Or possibly the harmonic balancer as I am not entirely sure how that works or how I would determine it was failing at its job. Under load the A/C vibe seems to smooth out. The jeep does have some highway vibes from ~58-65 mph that feel similar to the A/C vibes, and can be felt in the gas pedal particularly.
I also wonder if I have an engine vibration caused by the A/C compressor (aftermarket), the 136A alternator (aftermarket) or even the power steering pump (sourced new from PSC but works badly at idle). I’m a little at a loss, I thought the straight six was supposed to be a helluva smooth configuration.
The engine and trans internals are still something I don't completely understand, so I'm not sure whether to blame this on the stroker motor or the AX-15 that I had rebuilt. I don’t have time before I fly off for my next station in South Korea to just throw parts at this.
- recent work -
The jeep's at almost 252,500 miles now, and the new pilot bushing was put in around 4,000 miles ago. It took probably 1,500 miles for the shifting to start getting worse again, and it's now sometimes bad enough I am concerned I won't be able to get it in gear.
As far as the highway vibe, the driveshafts are probably OK. The rear was professionally balanced at a driveline shop, and has received a new CV yoke after I forgot to lube the old one. The front seems OK as received from Tom Woods. I removed and greased both driveshafts 1,300 miles ago and inspected the U-joints and brought them to a shop for a second opinion. I was told they’re fine.
The outer yoke nuts on the diffs are tight. The rear yoke on the T-case was pretty loose for awhile, and tightening it has gotten rid of some vibes I was chasing at the time ~2000 miles ago. Front yoke nut was fine.
I’m going to recheck my driveline angles hopefully today in between other errands, but they were shimmed as part of the lift kit I bought from DPG Offroad.
The axleshafts are a possible vibe source as they’re aftermarket. The rears are Yukons. Forgot the front brand.
Tire balance is another vibe source I know. I have black Cragar steelies all around (one new) that have been somewhat abused but professionally balanced by a Goodyear outlet in OK and are as smooth as they've ever been. They might cause my highway vibe, might not.
I have changed so much on this jeep it’s hard to eliminate various factors, but I’m trying.
I know this is long, but I'm trying to get the detail questions out of the way up front.
- problem -
The problem is that I was having a really hard time getting the trans in gear (AX-15) sometimes especially when stopped. First gear required a lot of hunting for Fourth or Second and Fifth and then I could catch First. This is frustrating spending three or four seconds doing this at every stoplight - though I could usually get the jeep in First at a slow rolling speed that meant holding the clutch in for the whole time the light was red and eventually that'll ruin the throwout bearing.
I took the jeep to a local shop in Lawton, OK and they separated the engine and trans and supposedly the pilot bearing just fell right out of the back of the block. They replaced the pilot bearing with a poly bushing (much like the 258 ci engine takes) and the problem was fixed for a while, but it has reared its ugly head again in exactly the same way. I have a Hurst short-throw shifter on the trans which I am sure is exaggerating my problem, but I don’t think it is the source as the issue comes and goes mysteriously. I’m removing it shortly to compare how it feels with the old stocker.
- background / other info -
The jeep is a 1998 with a Russ Pottenger-built 4.5L stroker made out of a '96-98 block, and the original AX-15 rebuilt ~17,000 miles ago. I have been chasing vibrations on and off, and I keep wanting to blame the vibes on the engine because they're bad enough that I’ve lost two fuel rail bolts and the rear header/manifold bolt keeps backing out and my exhaust downpipe flange bolts keep vibrating loose as well (with new exhaust hangers). I also had to change the rear main seal twice since the engine swap and it looks like the new one is seeping almost immediately.
The engine is largely smooth at idle but using the A/C brings on a nasty vibration that I'm still trying to understand, and I am wondering if something is off in the balance of the engine internals. Or possibly the harmonic balancer as I am not entirely sure how that works or how I would determine it was failing at its job. Under load the A/C vibe seems to smooth out. The jeep does have some highway vibes from ~58-65 mph that feel similar to the A/C vibes, and can be felt in the gas pedal particularly.
I also wonder if I have an engine vibration caused by the A/C compressor (aftermarket), the 136A alternator (aftermarket) or even the power steering pump (sourced new from PSC but works badly at idle). I’m a little at a loss, I thought the straight six was supposed to be a helluva smooth configuration.
The engine and trans internals are still something I don't completely understand, so I'm not sure whether to blame this on the stroker motor or the AX-15 that I had rebuilt. I don’t have time before I fly off for my next station in South Korea to just throw parts at this.
- recent work -
The jeep's at almost 252,500 miles now, and the new pilot bushing was put in around 4,000 miles ago. It took probably 1,500 miles for the shifting to start getting worse again, and it's now sometimes bad enough I am concerned I won't be able to get it in gear.
As far as the highway vibe, the driveshafts are probably OK. The rear was professionally balanced at a driveline shop, and has received a new CV yoke after I forgot to lube the old one. The front seems OK as received from Tom Woods. I removed and greased both driveshafts 1,300 miles ago and inspected the U-joints and brought them to a shop for a second opinion. I was told they’re fine.
The outer yoke nuts on the diffs are tight. The rear yoke on the T-case was pretty loose for awhile, and tightening it has gotten rid of some vibes I was chasing at the time ~2000 miles ago. Front yoke nut was fine.
I’m going to recheck my driveline angles hopefully today in between other errands, but they were shimmed as part of the lift kit I bought from DPG Offroad.
The axleshafts are a possible vibe source as they’re aftermarket. The rears are Yukons. Forgot the front brand.
Tire balance is another vibe source I know. I have black Cragar steelies all around (one new) that have been somewhat abused but professionally balanced by a Goodyear outlet in OK and are as smooth as they've ever been. They might cause my highway vibe, might not.
I have changed so much on this jeep it’s hard to eliminate various factors, but I’m trying.