Looking at a 68 Dodge 100 with a slant six and a four speed. The code on the door says it has a 3.55 ratio. Would this be a sure-gip unit? I have heard alot of the slant six trucks had them..

Thanks for the advice!

I have yet to find any external ID to denote a Sure Grip is inside. The "spin the wheel" test is the most simple way. If no axles are in the housing, you'll have a hard time knowing without pulling the 3rd member out for a look.
Oh, the ratio has NO association of whether or not a Sure Grip is inside. I'm told that any ratio could have been ordered with S.G.

it is way more possible to find a sure grip in a 2 wheel drive than a 4 wheel drive because there are few special order trucks---mopar figured if you had 4X you didnt need it----i checked my 71 door tag on a non sg truck and nothing is there---i am sure i have seen it noted on other trucks at the pickapart it is stamped in on the open equipment spaces at the bottom of the tag---bob

I have owned around 20 61-71 Dodge trucks and most had 3.55 or 3.91 open diffs, I have rarely seen a suregrip in one of those style trucks, and they were ALL 741 cases.

Look on the door tag for any boxes that reference the rear axle type. Most of the ones I've looked at are like this one http://www.t137.com/registry/help/canadiantags/images/w1j2963002.jpg or this one which is likely the one you have. It's for a C500 but the D100 will be similar. http://www.t137.com/registry/help/canadiantags/images/4586002338.jpg It should say either Sure Grip or SG in the Rear Axle/Make box.

Kevin

I pulled over a hundred 3.91 sure-grips from '60s vans and pickups. Around here, a sure-grip is fairly common if the vehicle was equipped with 3.91 gears. A van or pickup equipped with a 3.55 or 3.23 sure-grip is much more uncommon, however.

BTW, the presence of a quarter sized thrust block in the differential does not negate the possiblilty of a sure-grip. '69 and newer cone sure-grips used the same thrust block as open differentials. A pair of narrow side gear splines per side will positively identify a cone sure-grip.

Ok thanks for the information everyone. I will try to strike a deal on the truck and see what happens!

Another part to take a good look at is the hood, it is a one year only design though it looks like the 61-67 hood the bottom lip goes straight across while the earlier ones do not.

I agree with Cass.
It seems I find a lot of sure-grips in the mid 1960's to mid 1970's 2wd Dodge trucks & Vans.
Just this past week I bought an A-100 Van and an 1970 Dodge truck, both with 8-3/4" axles, 3.91:1 gears, and sure-grip differentials...and best part was I got both for scrap price!
Both vehicles have the 5 x 4.5" 'car' bolt pattern as well, so one will work great for our own hot rod truck!
They are both '741' 3rd members.



Dodge A-100 Van 318 engine, 3-speed manual transmission (column shifted), 8-3/4" 3.91 s/g axle:











1970 Dodge short box truck. 225 slant six engine, 4-speed manual transmission, 8-3/4" 3.91 s/g axle:

Most of the time, there is nothing to designate sure-grip on the body tag.

I've never seen the "39AS" code. I assume AS is short for "Anti Spin".

I occasionally see a separate decal under the tag printed "TC lock" (Traction Control?). I usually see this decal on fleet vehicles.

Once I saw a tag that read "39NS" (No Spin aka Detroit Locker).

Even some big block trucks got the 1 3/8" pinion. I had an original '68 383 4-speed D-100 equipped with a 3.55 open 741 case.

I've never pulled a 742 case from a truck or van, but I have removed a few 489 cases from '69-'71 4 x 4s. 489 cases are very common in vans and pickups newer than 1971, however.

I think 1972 was the last year for the 741 case. As far as I know all '73-'74 vehicles equipped with 8 3/4" rears got the 489 case.

Ok, looks like I made a deal on the thing at about scrap price. Hopefully it will have a decent set of gears in it!!!

I used to live in Spearfish, and I scrounged many sure-grips from pickups and vans in the area.

Unfortunately, 3.55 sure-grips are much less common in '60s vans and pickups than the 3.91 version.

even if it doesn't have a sure grip it is still worth the $$

A nice 3.55 open third-member is worh about $200.

Spearfish huh? Have you been out here recently? That Spearfish-Sturgis area along I-90 has really grown. Spearfish has been turning into a yuppie town slowly over the past few years! Rapid City has grown a little too.

I usually won't hesitate to buy a parts car, but I know so little about the trucks, so I had to ask a couple questions! Thanks Again!

I also agree with Cass. I fine alot of 391's and even 355's in trucks and vans. Mostly get 391SG's from 4wds. Just picked up a 67 D100 383 w/355. Hoping it's a SG. Haven't checked yet.

I lived in Spearfish from '88-'93. Until '05, I came back for a couple weeks every summer to scrounge rearend cores.

After my grandpa died in '05, the only time I go to SD is when I drive through on the way to Mopar Nationals every year.

My mom was born in Deadwood and my relatives live in Lead. My wife has relatives in Sturgis and Hermosa. My sister in law grew up in Rapid City.

My family also owns a cabin in the Black Hills (by Rochford).

That's awesome! I have been on vacation To Polson a few times too, I really like that end on the state and Glacier is one of my favorite Nat. parks,