1994 toyota pickup 4x4 22re 4 cl. I replace the engine and clutch. Onces the truck is run for about 30 mins. I find it stiff in getting to ist gear after a stop. I also sometimes hear the gear grinding when shifting to 2nd and 3rd gear. The transmission doesnot slip and the truck runs well. Just that stiffness to get it in ist gear after a stop sign and sometimes gear grinding on 2nd and 3rd gear.

Sounds like the clutch.

It can be the issue with weak battery or faulty battery or if battery is ok,then its faulty starter causing the issue.

From start to end troubleshooting these problem i suggest you to click the link below and follow its procedure:-----

What to Do When Car Turns Over But Won't Start?

http://technoanswers.blogspot.com/2012/11/what-to-do-when-car-turns-over-but-wont.html

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Car starting issues?

http://technoanswers.blogspot.in/2012/02/car-starting-issues.html

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Car Starting Problems

http://whoisbyme.blogspot.in/2012/06/car-starting-problems.html

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1991 Toyota Trecel: Engine Starts fine but dies when gets Warm?

http://whatisbyme.blogspot.in/2012/05/1991-toyota-trecel-engine-starts-fine.html

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1994 Toyota Pickup: Starts fine but dies in few seconds?

http://howtobyme.blogspot.in/2012/05/1994-toyota-pickup-starts-fine-but-dies.html

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1999 Chrysler Cirrus: 8 IGN Fuel Starter Fuse Blows?

http://whatisbyme.blogspot.in/2012/06/1999-chrysler-cirrus-8-ign-fuel-starter.html

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2001 Toyota Camry: No start After replacing Battery?

http://whatisbyme.blogspot.in/2012/05/2001-toyota-camry-no-start-after.html

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1989 Toyota Pickup Truck: Turns over but not start?

http://whatisbyme.blogspot.in/2012/05/1989-toyota-pickup-truck-turns-over-but.html

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Car dead and will not Start?

http://whatisbyme.blogspot.in/2012/05/car-dead-and-will-not-start.html

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1995 Lexus LS400: Running Hot?

http://whatisbyme.blogspot.in/2012/05/1995-lexus-ls400-running-hot.html

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2001 Toyota Prius will not start?

http://whatisbyme.blogspot.in/2012/05/2001-toyota-prius-will-not-start.html

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1996 Jeep Grand Cherokee: Engine will not start?

http://repairhelpcenter.blogspot.in/2012/06/1996-jeep-grand-cherokee-engine-will.html

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Mitsubishi will not start

http://www.howtorepairguide.com

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These will help.

Thanks.

This is a professional answer which it takes for us 4 hrs.I do not know for you.

Click the link below :----http://wikisolutions.blogspot.in/2012/02/get-free-answers.html

If you're sure that the clutch hydraulics are working properly ... then you are going to need to pull the transmission to see why the release isn't working .... bad throw out bearing, problem with pressure plate or ??

Trouble shooting here:
http://www.ncttora.com/fsm/1993/clutch/1troubles.pdf

Has your clutch been replaced. if yes how long ago?

No, By pushing in the clutch to stop the hum all you are stopping from turning is the transmission and ( transfur case if 4 wheel drive ) the engine is still running ..and some parts in the rear differential . I have had 4 nissan pickups and currently drive a 1995 pickup, without actually hearing the noise I would look toward the transmission, these Manual transmissions are very prone to bearing failure. This has happened to 2 of the one's I have had including the one I have now. You can also see as time goes by if the noise is quieter in fourth gear than others because this is direct drive and not as many trans bearings are involved Good Luck

What engine? four wheel drive?
Remove rear drive shaft, transfer case if it is four wheel drive, and front drive shaft.
Remove transmission.
Get the kit to replace clutch disk, pressure plate and throw out bearing.
If the flywheel is worn, or grooved, replace it or get it turned at a machine shop.

If you are leaking fluid from the clutch master cylinder then you have air in the system. You could try and bleed the air out of the clutch slave cylinder to get the gears but it would not last. The only way is to replace the defective master cylinder, replace all of the fluid and bleed out the air through the slave cylinder.

The clutch disk has broker, a piece of the friction disk material has boken loose and is wedged between the friction disk and the preasur plate. I had this happen to my '77 280Z. You will need to replace the friction disk.