RPMs with a 304/3 speed - JeepForum.com
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post #1 of 10 Old 08-17-2021, 04:05 PM Thread Starter
phylodog
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RPMs with a 304/3 speed

My CJ has been at the shop since shortly after I bought it. It came with a T5 which I'm told would slide right in. Apparently it came from another CJ with a Dana 300. The person I bought it from seemed to be knowledgeable so I took him at his word and sent the CJ off with the T5 for install. Now I'm wondering if this is going to be the case or if my transfer case isn't going to be compatible. If that turns out to be the situation I'm planning to have the 3 speed repaired (it locks in 3rd gear) and run with it for the time being.

What little I was able to drive it, the RPMs seemed extremely high for the speeds I was driving. If I remember correctly it was around 2800 RPM at 45mph. My question being; is this normal for a 3 spd? I'm wondering if a previous owner put 44's on it or something and with the 35s it has now it's geared funky.

Sorry if this doesn't make sense, I'm still learning about this stuff.

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post #2 of 10 Old 08-17-2021, 04:23 PM
Fourtrail
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the 3spd still has a 1:1 top gear same as any non overdrive transmission. even with 5.38's you are still running almost 55mph at 2800 rpm. have you verified the tach is set correctly and gps verified your speedometer? if you have 3.54 gears which were popular with the t-150 in 77, then you may have been in low range as 2800 rpm would put you at just over 40 mph.

80 CJ-5, 74 CJ-6, 56 CJ-5
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post #3 of 10 Old 08-17-2021, 07:42 PM Thread Starter
phylodog
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Originally Posted by Fourtrail View Post
the 3spd still has a 1:1 top gear same as any non overdrive transmission. even with 5.38's you are still running almost 55mph at 2800 rpm. have you verified the tach is set correctly and gps verified your speedometer? if you have 3.54 gears which were popular with the t-150 in 77, then you may have been in low range as 2800 rpm would put you at just over 40 mph.
I have not. I literally bought it, drove it twice and sent it to the shop. I'll dive into it deeper once I finish up some other projects around the farm and have more time on my hands. Thanks for the info.
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post #4 of 10 Old 08-17-2021, 09:00 PM
RiverandSand
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The T5 came in 80-86 CJs with a D300 xfercase. 79-76 had a D20xfer case. So chances are 5 spd won't mate up, unless you have the D300 too.
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post #5 of 10 Old 08-18-2021, 05:45 AM
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Originally Posted by phylodog View Post
I have not. I literally bought it, drove it twice and sent it to the shop.
No offense, but if you're gonna own a CJ, you need to rethink this idea, 'cause it'll cost you too much to fix too little.
You also need to take a deep breath and inspect your Jeep from top to bottom before you do anything. The unfortunate issue with CJ's is there is almost a pathological need to do some upgrade, any upgrade, to the rig. This means after forty years and a plethora of owners, you sometimes don't know what is lurking under the hood, behind the cover, or beneath the dash.

Knowing what gear ratio (you may have to drop the cover and count the teeth) and tire size you have will tell you what RPM's you should be running at certain speeds. If that is off, then you can look at what would cause it, which is usually a speedo issue, t case in low, slipping clutch, or transmission in wrong gear.
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post #6 of 10 Old 08-18-2021, 07:32 AM Thread Starter
phylodog
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Originally Posted by jeepdaddy2000 View Post
No offense, but if you're gonna own a CJ, you need to rethink this idea, 'cause it'll cost you too much to fix too little.
You also need to take a deep breath and inspect your Jeep from top to bottom before you do anything. The unfortunate issue with CJ's is there is almost a pathological need to do some upgrade, any upgrade, to the rig. This means after forty years and a plethora of owners, you sometimes don't know what is lurking under the hood, behind the cover, or beneath the dash.

Knowing what gear ratio (you may have to drop the cover and count the teeth) and tire size you have will tell you what RPM's you should be running at certain speeds. If that is off, then you can look at what would cause it, which is usually a speedo issue, t case in low, slipping clutch, or transmission in wrong gear.
No offense taken. You're absolutely right and this is my 3rd Jeep (had a YJ & TJ before) so I know what you're talking about. I was hoping to get this one road worthy before the cold weather sets in so my daughter could learn to drive a manual. Once I get it moving, stopping and steering well enough I'll be digging into things much deeper, I should have more time then as well.
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post #7 of 10 Old 08-18-2021, 01:05 PM
JEEPFELLER
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Just a little info from my end

I have a '77 with a 258

T-150 / model 20 transfer

3.54:1 Front/ rear

235/ 75/ R15 Tires

I've had a total of 7 CJ-5s since 1981---all being "onlys" and daily drivers. Most with the same driveline as my present CJ-5.

Having tachs in all of them, I can pretty much guarantee that 2200 RPM = 55 MPH maybe with very slight deviations +/- 50 RPM (if that) I have been eyeballing the tachs for 40 years!

-----JEEPFELLER
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post #8 of 10 Old 08-18-2021, 01:33 PM Thread Starter
phylodog
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Originally Posted by JEEPFELLER View Post
Just a little info from my end

I have a '77 with a 258

T-150 / model 20 transfer

3.54:1 Front/ rear

235/ 75/ R15 Tires

I've had a total of 7 CJ-5s since 1981---all being "onlys" and daily drivers. Most with the same driveline as my present CJ-5.

Having tachs in all of them, I can pretty much guarantee that 2200 RPM = 55 MPH maybe with very slight deviations +/- 50 RPM (if that) I have been eyeballing the tachs for 40 years!

-----JEEPFELLER
Thanks!
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post #9 of 10 Old 08-18-2021, 03:07 PM
JEEPFELLER
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Mistake in my last post.

Have had 6 CJ-5s (not 7) and presently the '77 and my '46 Willys.

I did not have #5 very long, as you can see the previous owner ruined him with the big wheels, can't rely on his tach info. He was descent otherwise, I only gave $600 (he was dead and P.O gave up on him) It's amazing what a new ignition module can do!

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post #10 of 10 Old 08-21-2021, 04:27 PM
80cj
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Originally Posted by RiverandSand View Post
The T5 came in 80-86 CJs with a D300 xfercase. 79-76 had a D20xfer case. So chances are 5 spd won't mate up, unless you have the D300 too.
The T-5 was not available in 80. Only manual transmissions in 1980 CJ's were SR4 and T-176.
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