rajsid

My 69 has a 3 year old 3:08 differential.
The PO was extremely proud of the 3:08 diff he had put in.
Is this a good diff?

What type of differential oil should be used for this diff?
Synthetic?

brs6482

Some of the guys LOVE the 3:08 because of the cruising speeds you get with the muncie. I have had one and it was nice. Kind of a pig but good for cruising. Standard rear-end fluid but donr forget the limited slip fluid (if yours has a limited slip) I get mine from GM.

GTR1999

308 is just the ratio. It was used on automatic cars and BB cars a lot.
What was he proud of, the way it was built or that he put it in?

Use Lucas 85-140 gear oil and GM additive.

rajsid

Thanks GRT,
He was proud of the fact that he paid $850 total to buy a rebuilt one from one of the big names and professionally put it in.

(I am proud of the fact that he did not do it himself )

Me80C3

I have the 3.08 and love it. I'm not into 1/4 mile, just a good cruiser. Putin' in a 3sp stick ( manual ) w/od in to get 75mph at 2300 rpm. It'll be behind a 450 horse 454. I'm usin' the 3 sp, cause I already have it.

68/70Vette

A really good combination with a 3.08:1 is a Richmond 5 speed. It will really wake up the car. The Richmond's fifth gear is a 1:1 just like the Muncie so you get the same good cruising performance. But the Richmond's first gear is much lower than the Muncie. With the Richmond in first gear, your car will have equivalent gearing of 4.11:1. In other words, in first gear, your 3.08:1 Richmond car will be geared the same as a car with a Muncie and a 4.11:1.

Chuck-75

I have a 75 and did the remove and replace myself.after cleaning the diff. and bringing all new parts to a pro that knew what he was doing to rebuild my diff. (he charged me $250.00 for rebuild)and after reinstalling the rear. I cant imangine anyone charging less then $1000.00 just for labor . the rebuild is pretty simple, but wow it takes a LOT of work for the Reinstall.
I used 2 bottels of GM Posi rear additive with heavy weight 80 oil.
Not related to yr question, I used Carbon fibor clutches and heavy duty springs. its a tighter rear and tires chirp a little around courners but I have a 425HP enging so I tried to go stronger.
$850.00 for a total remove and rebuild and replace? some where someone had to cut corners... if it was taken to a shop and had them do all the work........hope this helps.

Chuck-75

Opps forgot, with the 3:08, I had a th400 and with the stock engine the rpms would be around 2600 on the highway doing 55mph. modern cars dont run this high.
this is a great gear for daily driving, if yr looking for harder launches off the light, a higher gear will be yr choice.
anoughter choice is going with a 4 spd auto. the 200r4 or 700r4 will be a good choice with the 3:08 rear gear and give good off the line and good low rpm highway speeds. and will work with engine mods.
sorry I dont have much experience with manual trans with this rear gear...
just a home shade tree mech.

rajsid

[QUOTE=Chuck-75;1563683507]another choice is going with a 4 spd auto. the 200r4 or 700r4 will be a good choice with the 3:08 rear gear and give good off the line and good low rpm highway speeds. and will work with engine mods.
QUOTE]

I was thinking of a Keisler 5 speed down the line.
Good choice with this rear end?

knodty

Chuck75 are you sure about your figures as my th400 and 3.08 gave me 2700 rpm @ 70 mph the same as a buddy of mine who has a 68 427. I know mines a 3.08 as i checked the ratio last week as i'm just installing a th200r4. Don't know if any one else has the same figures as me or i've missed something somewhere.

GTR1999

Not trying to flame you here but the fiber clutches are not a good choice for a performance setup, they deleted a set of clutches and plates when switching from the junk snowflake clutches. I've had those clutches break down in my fingers. The 2 bottles of additive are good as I expect those clutches to hammer. You may be better off with 85-140 Lucas oil over the 80-90 wt gear oil.

stinger12

I'm sure your fiber clutches will be fine, but they definitely won't last as long as the full steel ones. Listen to Gary, he's a professional when it comes to differentials.

jim2527

I put 80-90wt Lucas in my diff. with 1 bottle of friction modifier. will that be an issue or should I change it out to 85-140wt.? Its a street driven car. No performance stuff.

GTR1999

Yes you can use the 80-90wt I just prefer the 85-140 Lucas. It seems to cling to the gears better then the std gear oil. No scientific tests behind this just personal experience.

As for the fiber clutches ask Tom about them sometime. I believe they ran them in a drag car,... once.

spedaleden

[QUOTE=rajsid;1563683958]
Keisler is great. The 5 speed give you better performance and smoother shifts and 5th gear keeps the engine from screaming. I had a 2:72 rear end gear in mine and put a 3:55 in. Car pulls a lot better and engine runs 1800 RPM at 80MPH.

TWINRAY

TH400 and 3.08 here and at 80, both needles straight up - 3 grand.

Brandywine

I have a 3.08 rear with the Keisler TKO500. I get the best of both worlds. The tranny and rear works out to be somewhere in the 3.90-4.0's in 1st gear and a 5th gear that I have not found top end on yet.

rajsid

That's what I want to put in
Does it matter what type of motor or flywheel you are running?

Brandywine

I don't know the specs for your BB motor...or existing tranny auto/manual? In any case I would talk with Richard of Keisler's tech support. His member name on CF is rj8806. Send him a PM with your info and he'll let you know what you'll need and what it will cost.

rajsid

Thanks will do...