High RPM's with 33's and AMC V8

Hey Everyone,
Ever since I did my CJ8 transmission project, I've had very high
RPM's. I put in a AMC 360 with a 727 tranny and CJ Dana 300 t-case.
It's a reman transmission, stock replacement for a J Truck / Wagoneer /
Cherokee. The engine is from the same heritage vehicle, a used engine.
I put new gaskets and Edelbrock intake with a Holley 4 bbl. The axle
is a stock AMC 20 with one-piece axles and 2.73 gears and 33" tires.
Yes, 2.73's. Things work great, except I'm running very high RPM's.
60 mph (actually 55 on the speedo) is running at 3000. 70mph (65 on
speedo) is 3200-ish, and is the "smooth" spot on the whole combination.
You can imagine what this is doing to my gas mileage, and that keeps
me from driving it. A round-trip to/from work is 24 miles. And a 1/4
tank of gas. I would like to keep this setup, but if the rpm's can't
go down I have no choice but to start over again. Of course a torque
converter will only affect the low revs, not the whole range.

Ideas? Advice?

Thanks,
Don W

Um, have you considered the fact that you have to make sure the ratio
inside your axle has to be a good match for your tranny? It sounds to
me like your axle ratio is just way too low for the transmission's final
drive ratio. Like possibly the axles have a 4.56 but 3.73 would be
better, though that is just an example since you didn't say what your
current axle ratio. Whatever it is, the fix is to install a higher
ratio set of ring & pinion gears inside your axles.

Jerry

QuickTruck wrote:
> Hey Everyone,
> Ever since I did my CJ8 transmission project, I've had very high
> RPM's. I put in a AMC 360 with a 727 tranny and CJ Dana 300 t-case.
> It's a reman transmission, stock replacement for a J Truck / Wagoneer /
> Cherokee. The engine is from the same heritage vehicle, a used engine.
> I put new gaskets and Edelbrock intake with a Holley 4 bbl. The axle
> is a stock AMC 20 with one-piece axles and 2.73 gears and 33" tires.
> Yes, 2.73's. Things work great, except I'm running very high RPM's.
> 60 mph (actually 55 on the speedo) is running at 3000. 70mph (65 on
> speedo) is 3200-ish, and is the "smooth" spot on the whole combination.
> You can imagine what this is doing to my gas mileage, and that keeps
> me from driving it. A round-trip to/from work is 24 miles. And a 1/4
> tank of gas. I would like to keep this setup, but if the rpm's can't
> go down I have no choice but to start over again. Of course a torque
> converter will only affect the low revs, not the whole range.
>
> Ideas? Advice?
>
> Thanks,
> Don W
>

--
Jerry Bransford
PP-ASEL N6TAY
See the Geezer Jeep at
http://members.cox.net/jerrypb/

Hi Don,
You mentioned torque convert, as if it may have a stall speed, if
so that's your three grand. As seventies five miles an hour through 2.73
ratio on 33" tires is only two grand:
http://corvetteactioncenter.com/tech/tools/rearend.html
God Bless America, ßill O|||||||O
http://www.billhughes.com/

QuickTruck wrote:
>
> Hey Everyone,
> Ever since I did my CJ8 transmission project, I've had very high
> RPM's. I put in a AMC 360 with a 727 tranny and CJ Dana 300 t-case.
> It's a reman transmission, stock replacement for a J Truck / Wagoneer /
> Cherokee. The engine is from the same heritage vehicle, a used engine.
> I put new gaskets and Edelbrock intake with a Holley 4 bbl. The axle
> is a stock AMC 20 with one-piece axles and 2.73 gears and 33" tires.
> Yes, 2.73's. Things work great, except I'm running very high RPM's.
> 60 mph (actually 55 on the speedo) is running at 3000. 70mph (65 on
> speedo) is 3200-ish, and is the "smooth" spot on the whole combination.
> You can imagine what this is doing to my gas mileage, and that keeps
> me from driving it. A round-trip to/from work is 24 miles. And a 1/4
> tank of gas. I would like to keep this setup, but if the rpm's can't
> go down I have no choice but to start over again. Of course a torque
> converter will only affect the low revs, not the whole range.
>
> Ideas? Advice?
>
> Thanks,
> Don W

If you are using the tach from a 6, it will be reading about 1/4 high on
the rpm......

Other than that, your torque converter must be shot and slipping like
mad to rev that high with 2.73's....

Are you sure about the 2.73 ratio?

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's

QuickTruck wrote:
>
> Hey Everyone,
> Ever since I did my CJ8 transmission project, I've had very high
> RPM's. I put in a AMC 360 with a 727 tranny and CJ Dana 300 t-case.
> It's a reman transmission, stock replacement for a J Truck / Wagoneer /
> Cherokee. The engine is from the same heritage vehicle, a used engine.
> I put new gaskets and Edelbrock intake with a Holley 4 bbl. The axle
> is a stock AMC 20 with one-piece axles and 2.73 gears and 33" tires.
> Yes, 2.73's. Things work great, except I'm running very high RPM's.
> 60 mph (actually 55 on the speedo) is running at 3000. 70mph (65 on
> speedo) is 3200-ish, and is the "smooth" spot on the whole combination.
> You can imagine what this is doing to my gas mileage, and that keeps
> me from driving it. A round-trip to/from work is 24 miles. And a 1/4
> tank of gas. I would like to keep this setup, but if the rpm's can't
> go down I have no choice but to start over again. Of course a torque
> converter will only affect the low revs, not the whole range.
>
> Ideas? Advice?
>
> Thanks,
> Don W

Hey Guys,
I just talked to a friend that's been working in a tranny shop for 10
years. He said the torque converter will indeed only affect the
low-end speed. He suggested slipping as well, but it's been this way
for over 1000 miles, and it wouldn't last that long if it were
slipping. The fluid is still full and cherry red.
I hadn't thought about the tach, i guess it's time to get one from
Collins Brothers to read 4,6 or V8. Once that happens i'll worry more
about it. I need to replace axle seals this weekend, i will check the
gear ratio for the third time. I counted teeth before, I wasn't
relying on the axle code.

Thanks,
Don W