Hog
Joined: 11 Dec 2001
Posts: 5016
Location: 1997 Chev ECSB L31 350 1997 GMC Sierra SLE RCSB, Ontario
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Thanks for the update.
1)How much did your cruise rpm increase?
2)Stock exhaust?
3) What kinda tire height are you running?
I wonder if this was a non-Direct IUnjection engine like in the GMT-800's/900's if the swap to 3.73 would still leave you short on the off idle/midrpm torque'ish feeling? The L83 5.3/L86 6.2, heck even the 4.3 LV1 are strong in that area.
When I went from 3.08s to 4.10s in my newish 1997 rcsb GMT-400 L31 350. It went from a 1700rpm- wouldn't hold OD/lockup on a grade a 70mph, to a held 4th gear/TCC lockup at 65mph with the cruise engaged on the same exact grade. I would "breeze" my right foot on the accelerator and the cruise control motor would barely even command more throttle to climb the grade. With the 3.08s, I could feel the pedal drop by about an inch, then the TCC would unlock and the trans would drop from OD to 3rd trying to maintain its cruise speed on that hill.
The 4.10s were awesome for city, 50mph driving and for quarter mile racing as I would trap in 3rd gear at about 4900rpm(stock rating was 255hp@4600rpm/330lb/ft torque@2800rpm). With the 3.08s I would trap at 49
However when late for work, or just attempting to emulate the "SPeeder", kicking the cruise speed up to 75mph resulted in an uncomfortable 2600rpm cruise rpm. With the 3.08s, that same 2600rpm could have me at the stock speed limiter at 98mph in OD locked up, but normal 75mph cruising was a much more relaxed 1900rpm.
I realize that describing a 2600rpm cruise rpm as "uncomfortable" sounds odd, esp. coming from a time when my first trucks came stock with 3 speed autos with no OD, but I also rocked 285.70/15(31" BFGs) and the 315/70/15 (33" BFG SPort Truck T/A H rated tires) in the older square bodies. I know you remember your Dad's or Brothers or your GrandDads(sorry cant remember) square body with the 400 SBC, IIRC it was a 1976 Chev???.
I loved those trucks as they had the "vent" style triangle windows that were perfect for ventilating the cabin. Just crack it a bit and it would suck you cigarette smoke right out and to ash, you just had to flick your smoke in the general vicinity of the vent window and aerodynamics would take over. Of course in the Winter up here, the occasional "snowdrift" would accumulate on the inside of the door if you didn't take extra care in properly closing the vent windows. Mine always leaked as they were old and well used.
peace
Hog
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