With that "thumper" cam you prolly gonna need a small converter with a high stall so it will idle while in gear(like traffic lights/ANY bumper to bumper stuff)  Its pretty snotty at low RPMs.   Jus say'in

3.50:1 for street use.Like MS sez.
(4.11:1 for street/strip stuff & of course trac-loc with this set up)

The wide ratio gearset of the 4R70W, will make 3.5 rear gears act like 4.11 gears in 1st and 2nd gear.
Limited slip is always a good choice.

Im running 3.50 with my 4r70w and 351c, 3.73 would be more fun probably. Im gonna stroke the 351c in 2 month so I leave the 3.50 for now, I had the original converter rebuilt, car Idle with no problems at 800-850 rpm. Stall should be around 2200-2300 and I think its an 11 inch converter.

Last edited by Mach173 (8/26/2020 11:19 PM)

I have a 3.73 in my 8.8 with the T-5 and works well for my driving, but I like a shorter gear and spend 90% of my time around town. My T-5 has the 3.35 first gear and anything shorter than the 3.73 would make first almost useless. My 66 had a T-5 with the 2.95 first and a 8" rear with a 3.80, this was a great combination, that car had a 393 which made lots of torque as well. MS has the formula listed but its all about the combination of gear ratios between the trans and the rearend.

I always have to go through this with my old Dad when I say I'm going with a low gear in the rear and I mention 3.73 or even 4.10, he will always laugh and say he would run back in the day 4.56 on the street and 5.13 at the track, and I have to explain he had a 4 speed with a 2.40 first gear.

I have a 416W stroker with a 94 GT T-5. 1st gear is 3.35 with a 3.0 differential. It's a pretty good stump puller leaving the stop. Not always good. I installed a vacuum gage for other tests and calibrations and found that at 70 it cruise's real good in 5th with plenty of reserve power but the gage is reading 13 to 14 inches. In 4th at the same speed the gage is reading 17 to 18 inches which is actually good for better gas mileage, I guess, but not as good for engine wear. I'm sure there is a better combination somewhere. The performance of the whole combination is way better than the C4 was but that also might have something to do with the cam change as well.

Mike my car would feel quite peppy with 3.0 gears, as I'm still running the 2.50's.

HudginJ3 wrote:

I have a 416W stroker with a 94 GT T-5. 1st gear is 3.35 with a 3.0 differential. It's a pretty good stump puller leaving the stop. Not always good. I installed a vacuum gage for other tests and calibrations and found that at 70 it cruise's real good in 5th with plenty of reserve power but the gage is reading 13 to 14 inches. In 4th at the same speed the gage is reading 17 to 18 inches which is actually good for better gas mileage, I guess, but not as good for engine wear. I'm sure there is a better combination somewhere. The performance of the whole combination is way better than the C4 was but that also might have something to do with the cam change as well.

This is a similar setup to how most 5.0s left the factory.  They used the tall first gear to allow a 2.73 final drive to keep gas mileage high for CAFE, while the 3.35 1st gets it out of the hole quickly so it doesn't feel like a slug with 2.73 gears. 
 

On my old 65 coupe with 135K its little stock 289, C4 I have 2:79s and turn 2550 at 70MPH. I get 15 MPG with the AC blasting and the cruise on

M'stangermike.....
I have the 3.00:1 gear also. (I think I do...if I counted the revs right?!!) Anywho.....with a T-5 it comes on pretty good thru the first 2 gears. Third gear is veeeery long-legged in my application. Wringing it out to my self imposed red-line of 5500.......I have exceeded most legal speed limits around!
Its funny (butt-knott great for fuel economy) in 5th gear under 60 mph the engine still has a slight lope to it.  Sort-uva nascar action.....
I really need a  3.55/3.60:1 to  "get the engine up on the cam" and still maintain a legal speed limit of 70-80mph and prolly pick up a couple miles per gallon..
It really hasn't been a detriment to everyday performance though.
6sal6

6sally6 wrote:

M'stangermike.....
I have the 3.00:1 gear also. (I think I do...if I counted the revs right?!!) Anywho.....with a T-5 it comes on pretty good thru the first 2 gears. Third gear is veeeery long-legged in my application. Wringing it out to my self imposed red-line of 5500.......I have exceeded most legal speed limits around!
Its funny (butt-knott great for fuel economy) in 5th gear under 60 mph the engine still has a slight lope to it. Sort-uva nascar action.....
I really need a 3.55/3.60:1 to "get the engine up on the cam" and still maintain a legal speed limit of 70-80mph and prolly pick up a couple miles per gallon..
It really hasn't been a detriment to everyday performance though.
6sal6

You'll find 1st and 2nd too short with a 3.50 gear and a 5,500RPM redline.  The thing you have to keep in mind is overall gear ratio.  Most V8 applications are best with an overall first gear ratio of 10:1.  Anything more and it starts to feel like a low gear in a dump truck.  With a 3.35 first and a 3.50 rear gear your overall first becomes 11.7:1.  Right now its spot on at about 10:1.

This is why the Z spec T5 has the 2.95 first gear.  The gear ratios in the trans were designed to pair better with the higher rear gears most 5.0 owners had installed.  Pair the 2.95 with a 3.55 and you're at 10.5:1 overall in first.  I have mine paired with a 3.73 in my '89GT, which is 11:1 overall in first, but that engine has a 6,500RPM redline.

I used to be able to tell what gears a guy had in his 5.0 at the strip by where he had to make the 1-2 shift.  Its how I knew 4.10s were a bad gear for any 5.0 that was close to stock.  The 1-2 shift came almost right out of the hole, and put you in 4th at the big end going through the traps at like 4,000RPM.  A car with a 3.55 was actually faster because it cut a better 60' and ran through the traps in 3rd at redline.  I watched a lot of guys get frustrated trying to prove that more was better.  Like most things its about the combination, not one magic bullet part. 
 

Using your 10:1 guide, Tom, seems about right.  My 90 GT had 3.55 with the Z-box and felt perfect on the street.  The Heap with the AOD always felt pretty dead off the line.  Well, the AOD has a 2.40 first gear and with the 3.55 I have in the rear that's 8.5:1 which is a bit tall.  The new 4R with 2.84 first gear comes in at 10.0:1 exactly so it should feel a lot better.

OBTW:  I was "raised" by guys who said that first gear is "low gear" and third gear is "high gear".  So when I refer to a high ratio...4.10:1... I call that a "low gear" or short,  and a low ratio like 2.72:1 is tall or "high gears".  Just a difference in terminology and probably who first taught us this stuff...but it can be corn-fusing.

BB1

Last edited by Bullet Bob (8/29/2020 7:16 AM)

I had a 3.70 in my old car and I had a 3.50 setup.  Between the two I liked the 3.50 gear and it was for the reasons stated.  I had the 94 T5 with the quick first gear and the 3.70 with my engine setup wasn't as fun to drive on the street.

Now since you have an auto trans and can adjust your shift points I would think the 3.70 may actually be a fun gear to have.