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Author Topic: '89 wrangler turning 4500rmp @ 55 mph.?  (Read 6478 times)

Offline jeep wrang6

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'89 wrangler turning 4500rmp @ 55 mph.?
« on: October 25, 2005, 08:46:50 AM »
Hello. I just finished changing out a 4 cyl. with a manual trans. to a 6 cyl. (4.2L) with an automatic trnny(tf999). The jeep runs fine, and shifts fine, but once its in 3rd gear it seems like it should shift again.....? I have read about some tf999 having a lock-up torq. and some dont. Is there any way to tell if mine does? It just seems like the engine is working real hard in 3rd gear (and yes I am positive its in 3rd). If anyone has any info on this matter it would be greatlly appreciated. Thank-you.

Offline Bill Cooke

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Re: '89 wrangler turning 4500rmp @ 55 mph.?
« Reply #1 on: October 25, 2005, 10:13:39 AM »
It's hard to tell with the trans installed already. The difference is in the input shaft where the torque convertor slides on. A lock up trans has a machined down end on that shaft where a non-lockup trans has splines all the way out to the end. Most later 999's were lockup BUT like you say, some were not. You'd also know by the 300 RPM drop at about 2,200 rpms.

Looks like you need bigger tires to bring the RPM's down! 35's ought to do it.  ::)

Hope this helps

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