gear ratios
The truck is a 1988 R30 Silverado dually four door weighing in at over 6600 lbs. The horsepower will be 375 hp, 400 lbs. torque with a Turbo 400 3 speed. Towing a 30 ft Airstream at 7800 lbs. Would li...
Forum Discussion
blt2ski wrote:
BIG issue you have is the really gal first gear in trans. IE a 2.48 which equates to a an approx 4-1. Which equates to around a max piling grade of 22-14% @ 20k lbs. A Muncie 4 sp with 3.42s I'm pumpkins can do 30+% due to the 6.8-1 granny low.
So a 3.55 and th400, else suck from a takeoff standpoint. My 89 R3500 flatbed with a stock 4bbl 454, th400 @ 4.10 gears cold not go up very many steep grades, blew up grannies every 30k like clockwork!
Another option is 2st two gears from a th350/700r4. Or as mentioned, best is a built 700r4. Then you have a 3.1 5-1 with tc engaged, and a.71 I'd to slow engine Dow. 4.33s or 4.56 gears and a 700r4 would be a sweet setup.
Marty
Yep. If the OP goes with 3.55’s then there will be trans problems, lots of strain put in it with the higher gearing. If it were me I would install a built 700r4 with the proper gearing.
