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T177 / Gears change ?

Dilafert

Dilafert

Basic User
City
Bayamon
State
PR
Hi All,

My transmission is giving me problems and will need to rebuild soon.

I have trouble keeping speed on the highway over 50mph. I have a TF999 , 35 inch tires and 4.10 gears. I have a 258 engine.

After 50 miles revs are too high and is difficult to keep accelerating. It feels like the transmission needs to shift to a 4th gear.

I’ve been planning on changing transmission to manual for some time.

Will changing to a T177 manual transmission resolve this issue and the Jeep will ride better with the current gears or would I have the same problem after 50mph?

Trying to find the best option to resolve this. I like how it accelerates now in 1st and I’m concern that going to 3.73 will not have a noticeable impact or will loose the current power.

Thanks for the help,

F
 
Does your trans need rebuilt due to slipping?

A T177 and the TF999 have the same 1:1 ratio in high gear as neither has overdrive. At cruise the auto will have a small amount of torque converter slippage. I don't think switching to a manual will have any noticeable effect in performance compared to a good functioning auto.

At 50 MPH you should only be turning 2000 rpm. 4.10s with 35s is a pretty popular setup with non OD transmissions. Do you have a tachometer to verify engine RPM? Have you checked your speedometer vs a GPS to verify speed?
 
My brother had that setup in a CJ7. I could do 65-70 mph. Didn't try to go faster.
 
I’ve got a tf999, 4.09 gears and 33’s, no problem with highway speed or excess rpms. Try to get a tach on it and use a phone app like Waze to verify your speed. You should be running less rpm than me at a given speed.
 
I have the setup you are talking about T-177, 3.73. But with 33s with a 258. 258 has mc 2100. I love it. Enough pickup for around town (I think the T-177’s lower first gear makes a difference. Will cruise at 65 and hold speed uphill. 70 feels ok too but feels like it’s working a little harder. 80 is about as fast as it goes.
 
I check this morning the tach with gps and shows almost 3,000 around 60mph. I would like to be able to cruise at this speed. Would need to open the diff and confirm if the gears are actually 4.10 or 4.56. Thanks for the replies , this definitely help to continue looking for the problem before spending money on an incorrect fix.
 
Dilafert said:
I check this morning the tach with gps and shows almost 3,000 around 60mph. I would like to be able to cruise at this speed. Would need to open the diff and confirm if the gears are actually 4.10 or 4.56. Thanks for the replies , this definitely help to continue looking for the problem before spending money on an incorrect fix.
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At those rpm, I really doubt that you have 4.10 gears.
 
I'm thinking your gears are deeper then 4.10 :twocents:

After blowing up three T5's, I swapped the T176 back into my red Scrambler. With 4.10 axle gears, 33" BFG Mud Terrains, and a T176 transmission I was spinning 2,800 RPM 65-70mph.

I like to drive faster then 65, so I swapped in an AX15. I usually drive 75MPH at 2500 RPM, same axle gears/tires.

I also ran 4.10 gears with 35" BFG Mud Terrains (T176) when I first rebuilt the Scrambler. It was OK, but 4.56 would have been better IMO.

If you are spinning 3000 RPM with 35" tires, you might even have 4.88 gears, or your torque convertor is slipping something fierce :shrug:
 
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