hey y'all- Need help trying to figure out the best approach to getting a 61 chevy 3/4 ton to go down the highway and not be miserable. Truck has 283 with a th350 behind it and 4:10 rear end. Local axel shop said gears can't be swapped and they suggest 700r4. I worry it won't be able to handle that much weight -thanks
How many hills where you drive, and is it going to haul heavy stuff a lot? I guess if it were me, where I live, I would try to get lucky again to find the somewhat rare 3.2 ratio 8 lug rear from late 70s to late 80s Chev/GMC. I've found that a good place to look in junkyards, is in a fully optioned/fancy suburban. I also found one in a 79 4x4 pickup I have one in my 66 camper special 4x4, tired 350 with TH400, and it still tows heavy cars on a car trailer. RPMs seem fine on highway
I'm for the 700r4 with big trans cooler. A friend has chevy 2 with 411 gear and 4l60e rolls great on the interstate and still has 411 low speed pull.
700R4/4L60 trans were routinely used in 3/4 ton applications. The truck versions 'may' have heavier duty components.......or may not. Either way, a properly rebuilt unit would be up to the task and a good sized cooler would be desirable. Ray
Don't know how much dinero you plan to spend but my kid uses a late Allison automatic with O.D. behind his big block in his chevy pickup. Handles all the weight you'd care to pile on the truck and trailer. Yeah, it's a little "whiny" ...
7oor4 was stock in my 2 wd 3/4 burb ( hd 3/4 's or 4wd had the th400 ) in the mid 80's they used corvette parts ( gov and other parts in it to increase line pressure and shift points (found out on rebuild ) ) and you cannot tow a trailer in OD at all ( must be in direct ( 3) or you wipe the clutch in the convertor and trans as its a 3:20 gear in OD , I burned mine up trying to tow 4500# worth of car and trailer thinking otherwise ) you can haul some weight in the bed but watch for hills . a 4l60e is the same as a 700 except its electric controlled , they do make a 5 gear planetary which is stronger for the 60 but the gearing is the same . but since rebuilders and 4 x guys gotten into the scene they have built them (700's) up pretty stout and some are even fixed so the pressure cable is not needed and it doesn't shift hard . do some shopping you can find a strong one , or use a built up th350 with a Gearvendors unit if you can find one .
Price an overdrive transmission that is build appropriately...be sure to figure out the mounting, it's a bit longer than a TH350. Look around for a later model rear end. I'd be surprised if you really have a 4.10, I thought they were 4.57 normally? I put a 3.73 14 bolt rear from an 80s suburban in one of my old trucks, it worked out pretty well, aside from the rear being a bit wider than original. I also had an 80 C20 that came with the 3.21 rear. I had a 305 engine in it for a little while, it was a dog, I had to start in granny (4 speed trans), and it wouldn't go up much of a hill in high gear. Putting a 350 engine in the truck fixed that.
The van 14-bolts are single-float, so you can keep your hubcaps, and are narrower than the same-era pickup axles, if memory serves. A 700R4, with a good cooler, of the newest vintage you can find, would also do the trick.
May daily driver for years (recently) was a '61 Suburban. There's several ways to skin this cat. First, the rear ends: The drop-out center rear is a handicap, because friendlier gears aren't available. Neither is Posi. Well, not for anything near "reasonable," anyway. The HD rear end for our trucks from '60-'62, was a Dana 44. This was also the standard rear for GMC trucks. Oddly, the standard rear suspension for Chevys was coil/trailing arm, while it was leaf springs for GMC. The HD rear for Chevy was leaf spring, and for GMC it was coils and trailing arms! I don't know what your 3/4 ton came with. My Suburban came factory with the Dana 44, and I found a spare a while back too. Hunt around for a Dana, and you can swap any gear ratio you could ever want, and you can find cheap Jeep posi units too. I've got a 3.42 in mine. Up front, the 700r4 should be fine. You aren't doing heavy hauling, towing big trailers, etc. etc. If you want to swap to a manual trans, look for the MY6 4spd OD set-up. It's a New Process trans Chevy put in their trucks from '81-'87, and runs 4th gear as a .72:1 OD. I've got that in my Suburban too. I don't have a tach, but going down the highway at 80mph was effortless with the crate 350. If I kept it at 55mph, I could knock down 18-19mpg. At 75, that dropped perceptibly! Usually around 15-16mpg, with 235/70/15 tires. -Brad
You can find 3.55 gears in 71/72 3/4 ton pickups if you hunt a bit. They are a tad wider than the earlier axles so you can't run real deep rims but that would be the simple way out. I found one for my 71 GMC a couple of years ago but haven't tried it out yet.
The panhard bar length and its mount is totally different on the '60-62 trucks, and the mounting pads for the trailing arms are also slightly different widths.
HUH the truck or the tranny? I may try a different local axle shop and a 700R is just a t 350 with an OD it should hold up just fine. They may have meant that you need a different carrier to go with a taller gear, I would think that you could find a 3/4 rear with a 3.73 that is what my Johnny Cash '63 had.
Thanks Brad, would put it manual but she was a factory automatic so would like to keep everything stock. Will probably go for the r4 at the end of the day...
Silverado's for many years came with 3:55/3:73/4:10 ratios and the 4L60 60e trannys. My 2000 had a 3:73 4L60e combo and ran down the highway great. My Avanti has a 4:10 and 2004R 355 SBC combo and is a great highway cruiser. Bottom line, find a 700R4/4L60 and put it in. You won't be sorry, as a piece of advice when you are looking in a pick-n-pull for a tranny. Look for a clean one that should indicate it was recently rebuilt.
No such thing as a 4L80. That's a 4L80E. The E is for Electronic. They, along with the 4L60E require an expensive controller to operate them. Without it, they do not shift.
Sorry 4L80E,the were used behind 6.5 diesel and I do not believe they used the controller ,but I am sure you will correct me.
The Jalopy Journal
