I need to put a 3.73 gear in my, waiting for destuction, 7.5 rear end or upgrade with minimum wallet suction. Any help here?
Procure a used one from an S-10 at a salvage yard. Lots of them are 3.42, 3.73, and 4.11. '88 and earlier should be 26 spline. You can source a posi carrier from '93-up F-body but, that will require 28 spline Grand National or aftermarket axles......waaaaaaaaaaay stronger!
Contact me I have a 3.73 gears an posi unit form an 85 ss monte ---------- Post added at 08:18 PM ---------- Previous post was at 06:29 PM ---------- $200 plus shipping
People rag on the 7.5 GM axle saying it's not good for much more than a stock v6, but I have read a lot on the subject and get mixed stories. There are however, some key factors to consider: 1. The stock carriers were cast iron and weak. Even the F body 7.625 (which fit inside the 7.5 housing) were cast iron. They were stronger, but still relatively weak. 2. To remedy this, Eaton makes a steel 28 spline carrier (in either Torsen or clutches) that will practically eliminate flex which soft iron is notorious for, which holds the gears well in place and is many times stronger (F body racers claim to be able to regularly run 9's with this carrier in a 7.5). 3. The 8.5 everyone cheers on about uses 28 spline axles, so using a set of those for the 7.5 28 spline carrier should be just fine. Not to mention the aftermarket 28 spline steel axles you get from Moser (I think it is) are 30% stronger than the stock GN 28 spline axles. 4. Welding up the case will greatly reduce flex, as will: 5. Using a TA rear end girdle, which adds extra rigidity and helps hold the carrier bearings in place, as well as holding an extra 1/2 pint of oil and keeps fluid cooler. Use whichever gear set you want, though 3.23:1 is the lowest you can go using a 3 series carrier, and the higher you go, the smaller the pinion gear gets, which increases the risk of ring/pinion failure. Safe numbers are 3.23, 3.42, and 3.73 (being the highest you want to use). This setup won't hold up to supercharged stroker bigblocks, but should be safe for use with (my guesstimate) moderately built 350's and maybe a stockish low compression 455. Things to remember: shock energy kills a rear end. Jolting launches on slicks, manual transmissions, towing, etc. are to be avoided or limited. If the car never sees slicks, doesn't have a high stall, uses the 3.42 or 3.23 gears, I wouldn't be afraid to put a stock low compression 455 in front of it and expect it to last the lifetime of the car/combination. Bear in mind stock 7.5 stuff IS weak. You have to do these upgrades if you want this strength.
