Overdrive trans or change rearend/gears

[fourspeedwagon]

I thought I read a thread about this before but.. I couldn't find it now.
My 68 has a three speed manual trans and I'm guessing 411 rear gear (maybe steeper?) I don't have a tach in it but it's really singing at 65-70 mph. I can't bring myself to cruise with it any faster than 65 for any distance. I'm not a great mechanic- as much as I love cars, trucks, bikes, tractors and own many, I admit, I'm just not great with a wrench. That said, would it be easiest to change out the trans for an overdrive unit or just find a rear diff with 355 (or so) gears?
My rig is a 68 2 wheel drive half ton suburban, mild 350. I think I'd rather have a different trans cause the 3 speed is also a pretty slow shifting unit but I can live with it.
What do you think? Thanks

[hopped up]

i think its easier to change the gears in the rear. eventhough thats still alot of work, changing the tranny is gonna lead to a bunch of other little thing your gonna need to change also.
Posted via Mobile Device

[hopped up]

i think its easier to change the gears in the rear. eventhough thats still alot of work, changing the tranny is gonna lead to a bunch of other little thing your gonna need to change also. tranny mounts , driveshaft, new shifter, linkage?
Posted via Mobile Device

[crazy longhorn]

I like a mid 3's gear, & IIRC my longhorn ran about 73mph cruising @ 3000 (400 turbo & a 28" tall tire). OD is nice, but expensive to set up....if you do a lot of hyway, & no towing, you might also opt for a 3.07 gear to drop the cruise revs a little more. best of fun,crazyL

[mud.man.rj]

Seems like I am going against the grain but I would change to a 4spd trans, sure it is a bit of work but lots of trucks came with them so it is original equipt and lots of help here for sure and that way it will still be geared good for hauling a load especially the weight of a suburban plus you will get rid of the sucked out 3 spd. The extra gear is really nice. Apparently you don't like the 3spd anyway so nothing but better for you.

[cdowns]

changing to a 4speed tranny will result in zero difference in the cruising problem he has// 4speed has same 1:1 final drive ratio as three speed

[mud.man.rj]

Well than maybe look into a 5spd instead of a 4spd if final drive of 3 and 4 spd is the same. Many use a Camaro 5spd in a truck, they seem to hold up well for daily driving. Cheap alternitive. Personally I like a 4spd auto but my truck came with a 4spd std so leaving it stock.

[Beat68CST]

If you're not opposed to automatics put a 700r4 in it.
If you want a brute manual do an NV4500.

They're both overdrive.
Posted via Mobile Device

[special-K]

I think changing the transmission is far easier than changing the rear or the gears in the rear. You already have a manual,so an overdrive manual would be easy. It is also easier to go from manual to automatic. I also like the idea on trans change over rear change because you take nothing away from the Suburban's power. The trade off for taller gearing for better hiway cruising is gutlessness everywhere else. With on O/D transmission you have the same puling power "plus" a gear for the hiway.

[MARKDTN]

Originally Posted by special-K

I think changing the transmission is far easier than changing the rear or the gears in the rear. You already have a manual,so an overdrive manual would be easy. It is also easier to go from manual to automatic. I also like the idea on trans change over rear change because you take nothing away from the Suburban's power. The trade off for taller gearing for better hiway cruising is gutlessness everywhere else. With on O/D transmission you have the same puling power "plus" a gear for the hiway.

I agree. OD trans gives you "best of both worlds".

[mrein3]

I'd change the transmission. Stump puller and highway cruiser.

[PanelDeland]

Tranny swap.The carriers in these rear ends come in low and high style.Yu may be able to get mid range gears(3:55 aftermarket I haven't chaecked) but the others come in a 3:07 or 3:73.
Keep in miind that you are probably used to a modern OD and thy tend to run fewer RPM's than the older cars.My 250/6cyl/3OTT truck seems to have a "sweet spot" about 63 mph.I would love to have a Gear vendors but will probably wind up going to a 200R4 or 700R4.

[fourspeedwagon]

Is the nv a granny 1st gear? Also, will it work with my current clutch and bellhousing? Anybody done a build thread with this swap? Thanks again.
Posted via Mobile Device

[Wrenchbender Ret]

If you cant do the work yourself I think you will be better off getting a 3.08 rear end from a salvage & have it installed. When you start farming out modifications you can get into some problems & expense. An automatic changeover is even more difficult.

[caboutin]

I am in my 5th year of trying to figure out my 700R4 and I don't recommend anybody ever change over to one. Put a six speed manual in your vehicle and you will smile!!!

[mtdave2]

i put a gear vender in my longhorn, best thing i ever did.

['72customdeluxe]

Quiet mufflers and sound deadening are cheaper than either. I can cruise 80+ in my '05 in 3rd gear and can't hear the engine at all over wind noise. A loud exhaust at 2k rpm is more annoying than higher rpm noise to me. If you drive enough, the o/d trans will eventually be offset by fuel cost though.

[cdowns]

if you put a 308 rear in the truck will have to work very hard to move it's massiveness and probally result in worse gas mileage in the long run

[mud.man.rj]

Only problem if you regear is your still stuck with the old dated 3 speed that was never great in the first place.

[fourspeedwagon]

I don't do any severe duty type action with the 'burb. A t5 or nv4500 sounds good, anything else that I should be aware of in parts hunting for the swap?
Posted via Mobile Device

[mud.man.rj]

A friend of mine did the same swap and I think he had to change clutch disc for proper spline count and trans yoke, he did the T5 trans.

[mud.man.rj]

I think his trans tunnel hump was fine with the T5, larger for the Sm465 like in my truck.

[slomotion]

If you decide to go with a T5 look for a Mustang "World Class" (brand name) gearbox, and a Sonoma tail shaft to put the shifter in the right place. The Camaro/Firebird/'Stang T5 shifter is designed for bucket seats and puts the shifter to the rear of the tail shaft. IIRC, I don't think I had to change my clutch plate, but did have to cut 1/4" off of the trans input shaft to keep it from bottoming out in the flywheel. This was behind a 292 I6, so the 350 may be even easier. My T5 is a .83 OD, and the engine went from "scream" at 60 MPH, to 2800 RPM at 65 MPH. The T5 is quite, shifts great, and weighs less than your 3 speed.

[davepl]

If you're mechanically up to it, I vote transmission all the way. I have TKO-600 five speeds in my two cars and before that a 200-4R. In the B-Body I run 4.11s and once the overdrive gear kicks in it's like cruising with 2.73s... but at launch time the first gear makes it like having 5.14s. Truly the best of both worlds.

That said, if you don't enjoy the work, it's far easier to drop it off at an axle place and have them swap in a lower set of gears. There are seven people on earth who can set up a GM 12-bolt properly and four of them are dead, so don't try it at home.

[VWBeamer]

Agree, OD transmission will give you best of both worlds, great off the line and pulling power , and still have low RPMs on the highway.