'79 rear end

[boogieman]

I've read the rear in my '79 is a Dana 44 used in Jeeps, too.

Any idea what gears I might expect in it as built?

I've seen a pic of the rear but don't see a tag indicating ratio.

The current owner says he has never been in there.

Boogieman

[Avanti83]

My 74 4-speed came with a 3:23 I believe. I think the automatic was 3:07. That will give you an idea. Otherwise you could jack up one wheel and count the wheel rotation versus drive shaft rotation when turned by hand.. A word of caution however, this won't work with a posi.

The Avanti.net website has a lot of data on Avanti's but the problem is that during this period, there was precious little documentation on the exact specs. During this time period a lot of them were built to customer order. My 74 should have a 400 SBC but the OP wanted a 350 and got same.

Dan Booth at Nostalgic has most of the build sheets from this era so you might find it on that document.

Good luck, Bob

[boogieman]

Thanks Bob. I already have the build sheet. No notation regarding rear end gears or ratio. Had no idea what was "standard". The 3.07 is about perfect for me as Texas has lots and lots of straight level roads leading off in any direction. I plan some serious highway mile trips. By the way my '79 is equipped with an L48 350, turbo 400 auto and no Twin-Track.

[Charlie Kile]

My 84 Touring Optioned Coupe came with a 2.86 Twin Traction rear end. Don't know if all the TOCs came with that gear set. But for Highway cruising it works well. The change to a 350 HO also helps.

Charlie RQB3921

Edited October 24, 2013 by Charlie Kile

[Guest dapy]

Are there significant performance improvements with the HO variants of the 305 and 350? if so what are they and how do you know you have a HO?

[Devildog]

Thanks Bob. I already have the build sheet. No notation regarding rear end gears or ratio. Had no idea what was "standard". The 3.07 is about perfect for me as Texas has lots and lots of straight level roads leading off in any direction. I plan some serious highway mile trips. By the way my '79 is equipped with an L48 350, turbo 400 auto and no Twin-Track.

My 75 had a 3.07 with automatic tranny, 400 SBC. The prior owner had installed a 700R4. I rebuilt my differential and I wanted to go to a 3:55, but the shop convinced me to go to 3.70. With the 700R4 this set-up gives 11:1 (3.70 x 3.0) in first gear and 2.69 (3.7 x 0.7) in 4th gear, 2200 rpm@70mph. I went on a 200 mile trip (Houston to College Station) recently and averaged 22 mpg.

I have 3.08 gears in one of my old Corvettes and that makes a nice Texas road cruising gear, about 2900 rpm @70 mph.

Glade to hear you are planning trips in your 79, I have taken several 400 mile week-end trips in my 75 and it is comfortable. Everyone really enjoys seeing an Avanti on the road where God and Studebaker intended.

I am registered to drive it to the SDC Golden Anniversary 50th International Meet, June 28 - July 5 in Dover...come along

Joe

Edited October 24, 2013 by Devildog

[boogieman]

Giving that serious consideration. 50th Anniversary and all.

[plwindish]

With the THM 400 trans, you could have a 3:31 Dana in it also. There are tags bolted on the rear cover of the rear end that would be able to decipher what the rear end is. The tag would be located in the 8 to 9:00 position on the outside of the rear end, held on by the cover bolts. My 76 has a 3:31 twin traction. The twin traction is listed on the build sheet, but I don't think the 3:31 is listed. Take a trip down the road at 70 mph, if your rpm's are 3000, your rear end is probably a 3:31. I don't want to give you more work, but with you wanting to travel down the roads in the car, look into replacing the THM with a 200R4, or a 700R4 AOD trans. The AOD trans will drop the rpms at 70 mph by 1000 rpms. The 200R4 has been maligned because early versions were not beefed up enough. Getting one rebuilt today would be more than beefy enough for the 350. The 200R4 is also more ratio similar to the THM400 than the 700R4. The highway gear (4th) will drop the rpm's and improve miles per gallon.

Edited October 29, 2013 by plwindish

[boogieman]

Another good friend owns and operates a transmission shop. I will check with him on the 200R4. My understanding is that the 700R4 might require floor pan or trans tunnel trimming due to physical size. You know anything about that?

[Gunslinger]

I have a 700R4 in my '70 and there were no clearance issues. What was run into was new neutral safety and backup switches had to be fabled due to being too close the the 2 1/2" exhaust system I had installed in place of the original 2" design.

It seems to be a car by car thing whether a 700R4 makes for clearance issues. Essentially, if one already has a TH400, a 700R4 shouldn't have any problems.

That being said, many say that a 200R4 has a better spread of gears than the 700R4.

[Devildog]

Another good friend owns and operates a transmission shop. I will check with him on the 200R4. My understanding is that the 700R4 might require floor pan or trans tunnel trimming due to physical size. You know anything about that?

Nope, a 700R4 will slip in there easily. I took mine out to change the stall converter and install a lock-up... easy. 700R4 is one of the best things you can do especially if want to drive on the highway longer distances:

a. 3.3 first gear

b. 0.7 4 th gear will give you 2000 rpm or less at 70 mph. quiet, smooth, etc.

Joe

[boogieman]

Thanks Joe. Will check it out.

Boogieman